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A colorimetric molecular probe for Cu(II) ions based on the redox properties of Ru(II) phthalocyanines
Abstract
The one-electron oxidn. of a Ru(ii) phthalocyanine induces a dramatic color change and provides a useful tool for the selective and highly sensitive colorimetric detection of copper(ii) ions in neat aq. solns. [on SciFinder (R)]
... In recent years, some Pc-based chemical probes have been reported in the literature [34][35][36]. For instance, Achadu et al. were able to determine biothiols playing a critical role in cell metabolism, with an approach based on the fluorescence "off-on" mechanism. ...
... For this study, Pc macrocycle which has conjugated 18 π-electron system enabling strong absorption and emission in the visible and NIR regions was chosen as the skeleton structure for designed probe. The photochemical and thermal stability ensuring long lifetime and easily tunable ring system properties of Pc core make it inevitable to be used in the probe platform [16,17,25,[34][35][36][37][38]. Identification and transport of the most prevalent metal cations has been reported to be major challenges in different fields of chemistry. ...
The aim of this work is to construct a new A2B2-type of unsymmetrical and ratiometric phthalocyanine (Pc) based-probe O-A2B2ZnPc to provide an effective solution to critical inadequacy to be experienced for the detection of hazardous Be2+. O-A2B2ZnPc enabling strong absorption and emission in Near-Infrared region (λabs-λem wavelengths of 694-712 nm) showed excellent selectivity and sensitivity toward Be2+ among competitive metal ions by both spectrophotometric and fluorometric methods. The probe with oligomeric Pc form in THF was degraded with the addition of aqueous Be2+ and arranged to J-aggregation form, resulting in a remarkably diminishing in Q-band at 694 nm as well as a new band formation at 746 nm, and a considerably decreasing in fluorescence emission. The probe has superior features for the determination of Be2+ such as high quantum efficiency and photochemical stability, rapid response (1 s), high selectivity and very low Limit of Detection (0.26 ppb and 1.5 ppb) for UV-Vis and fluorescence, respectively which are quite good values according to the permissible amount of Be2+ (4 ppb) in water as specified by World Health Organization. O-A2B2ZnPc can be shown among the best performing probes with its unique properties according to previous studies in the literature. In addition, the geometrical and spectral features of the O-A2B2ZnPc were analyzed in detail by DFT calculations.
... On the contrary, the symmetric complexes Pc*RuL 2 are much more resistant to ligand exchange. So, in order to prepare the stable complexes Pc*RuL 2 one of the following methods can be used: the template condensation of phthalonitrile in the presence of ruthenium source and N-donor ligand [10,30,[35][36][37][38][39]; the replacement of labile benzonitrile molecules in Pc*Ru(PhCN) 2 by substituted pyridine ligands at 25-70 • C [4,5,7,34,40]. The starting complexes can be prepared either by template condensation of phthalonitriles with RuCl 3 ⋅nH 2 O [3] or by direct metalation of phthalocyanines with ruthenium carbonyl, Ru 3 (CO) 12 in benzonitrile [4,40]. ...
... So, in order to prepare the stable complexes Pc*RuL 2 one of the following methods can be used: the template condensation of phthalonitrile in the presence of ruthenium source and N-donor ligand [10,30,[35][36][37][38][39]; the replacement of labile benzonitrile molecules in Pc*Ru(PhCN) 2 by substituted pyridine ligands at 25-70 • C [4,5,7,34,40]. The starting complexes can be prepared either by template condensation of phthalonitriles with RuCl 3 ⋅nH 2 O [3] or by direct metalation of phthalocyanines with ruthenium carbonyl, Ru 3 (CO) 12 in benzonitrile [4,40]. In the latter case short-time reflux leads to carbonyl complexes Pc*RuCO [20] whereas overnight reflux of reaction mixture leads to ruthenium complexes with coordinated benzonitrile molecules in two axial positions Pc*Ru(PhCN) 2 [4]; the substitution of labile acetonitrile molecules in Pc*Ru(CH 3 CN) 2 by substituted pyridine ligands at 25-80 • C. The starting complexes can be synthesized from Pc*Ru(CO) via decarbonylation under UV-irradiation in acetonitrile solution [5,7,32]. ...
We report an extensive study of axial ligand replacement in ruthenium(II) complexes with tetra-tert-butyl-phthalocyanine (tBu4Pc). For this purpose oxidative decarbonylation of [tBu4PcRu](CO) in the presence of trimethylamine was performed providing [tBu4PcRu](NMe3)2 complex in 92% yield. Its heating with pyrazine in o-dichlorobenzene at 100°C gave [tBu4PcRu](Pyz)2 in quantitative yield. A simplified TD-DFT approximation has been used to explain the difference in the appearance of UV–Vis spectra of synthesized complexes with different N-donor ligands in terms of π-π* or charge transfer excitations, assignment was validated by the studies of solvatochromism of synthesized complexes. The reported finding can pave a convenient way to a relatively mild selective synthesis of ruthenium phthalocyaninates carrying N-donor aromatic ligands. Such complexes attract interest for various photo- and electroactive applications, catalysis and medicine.
... PS7-12 were prepared by replacemento ft he labile nitrile ligands in Ru(PhCN) 2 Pc or Ru(MeCN) 2 (PEG) 8 Pc, [28,30] by pyridyl ligands L4-6.U sually,t hese coordination reactions are carried out either in the neat pyridine derivatives if they are liquids, [37] or in chloroform, [14,28,30] toluene [37] or hexane [38] as reactions olvents. In this case, owing to the low solubility of ligands L4-6 in these solvents, we carried out their coordination to RuPc in DMSO at room temperature. ...
The synthesis of ruthenium(II) phthalocyanines (RuPcs) endowed with one carbohydrate unit—that is, glucose, galactose and mannose—and a dimethylsulfoxide (DMSO) ligand at the two axial coordination sites, respectively, is described. Two series of compounds, one unsubstituted at the periphery, and the other one bearing eight PEG chains at the isoindole meta‐positions, have been prepared. The presence of the axial DMSO unit significantly increases the phthalocyanine singlet oxygen quantum yields, related to other comparable RuPcs. The compounds have been evaluated for PDT treatment in bladder cancer cells. In vitro studies have revealed high phototoxicity for RuPcs unsubstituted at their periphery. The phototoxicity of PEG‐substituted RuPcs has been considerably improved by repeated light irradiation. The choice of the axial carbohydrate introduced little differences in the cellular uptake for both series of photosensitizers, but the phototoxic effects were considerably higher for compounds bearing mannose units.
In our research, we produced some novel porphyrin derivatives 4a–g in high yields. We also synthesized and characterized some of their metalloporphyrin complexes 5–11. The structures of these novel porphyrins were assured by spectroscopic techniques. The geometric structure and magnetic properties of metallo-porphyrins 5–11 have also been studied. Antiviral and antitumor activities were estimated and the structures activity relationships were accomplished. The Porphyrin derivatives 4g, 4f, 9, 10 and 11 displayed strong antiviral activity for HSV-1 compared to Aphidicoline as reference. While derivatives 4g and 6 exhibited very strong activity against HIV-1. Porphyrin derivatives 4g, 6, 9, and 10, in general, displayed strong activity against all the tested human cell lines.
The present review article focuses on fluorescent probes based on Ru(II)-polypyridyl fragments connected with different chelates, their significant roles in coordination chemistry and their applications in selective recognition of biorelevant Cu2+ and Fe2+/Fe3+ ions. A critical analysis of the detection of metal ions by both “turn-on” and “turn-off” nature, properties, mecahnism and applications of these sensors, is presented. Emphasis has also been laid down on the efficiency, selectivity and specificity of these sensors towards biologically important Cu2+ and Fe2+/Fe3+ ions.
A new amphiphilic near-infrared aza-BODIPY dye bearing both hydrophobic alkyl and hydrophilic oligo-ethylene glycol chains was synthesized by facile click reaction. By introducing the electron-donating N,N-disubstituted amino groups into the molecular structure, the new dye show outstanding absorption and fluorescence characteristics, specifically, absorption wavelength up to 850 nm and emission up to 950 nm, and fluorescence quantum yield of 0.29. The solvatochromic properties of the new dye were investigated by UV/Vis absorption and fluorescence spectroscopy. Furthermore, the electrochemical properties of the dye were studied by electrochemical cyclic voltammetry. The application of this dye for the detection of metal ions was further studied. The results indicated selective binding ability of the dye for Cu²⁺ ions and revealed its promising application potential as a near-infrared fluorescence probe.
Series of substituted µ‐carbido diruthenium(IV) bisphthalocyaninates [Pc*Ru]2(µ‐C) [where Pc* = tetra‐tert‐butyl‐, octa‐n‐butoxy‐, tetra‐15‐crown‐5‐ and hexa‐n‐butoxy‐mono‐(15‐crown‐5)‐substituted ligands] were synthesized using two alternative approaches – (i) direct metalation of phthalocyanines with Ru3(CO)12 in refluxing o‐dichlorobenzene where [Pc*Ru]2(µ‐C) are formed as by‐products together with monomeric complexes [Pc*Ru](CO) and (ii) dimerization of [Pc*Ru](CO) by dichlorocarbene generated in situ from chloroform and bases (KOH or NMe4OH), which affords target complexes in high yield. Application of the appropriate base – NMe4OH was found to be crucial in the case of synthesis of crown‐substituted µ‐carbido dimers. Reaction of Ru3(CO)12 with the phthalocyanine bearing bulky mesityloxy‐groups yielded solely monomeric complex which could not be dimerized under any studied conditions. Therefore, the influence of nature of peripheral substituents in phthalocyanines on their reactivity in metalation and dimerization reactions was revealed.
Phthalocyanines (Pcs) have been known for excellent electron transfer properties owing to their extended (Formula presented.)-conjugated structures. In addition, functionalized iron oxide nanoparticles (Fe(Formula presented.)O(Formula presented.) NPs) have attracted considerable interest owing to their unique spectral and electronic properties. Hence, it can be reasonably expected that Fe(Formula presented.)O(Formula presented.) NPs decorated with Pc molecules could provide a useful electrocatalytic system. Herein, we present the preparation and electrochemical properties of cobalt-phthalocyanine (CoPc)-decorated Fe(Formula presented.)O(Formula presented.) NPs ([email protected](Formula presented.)O(Formula presented.). The Fe(Formula presented.)O(Formula presented.) NPs were first coated with a silica layer to produce SiO(Formula presented.)@Fe(Formula presented.)O(Formula presented.). Subsequently, CoPc with a siloxane end group (CoPc-TEOS) was anchored to the outer surface of the SiO(Formula presented.)@Fe(Formula presented.)O(Formula presented.). The [email protected](Formula presented.)O(Formula presented.) thus prepared was fully analyzed using various characterization methods. Distinctive electrochemical responses of CoPc and [email protected](Formula presented.)O(Formula presented.) in the presence of picric acid were observed, demonstrating the potential application of the current approach to electrochemical catalysis.
µ-Carbido diruthenium(IV) phthalocyanine complex was prepared for the first time from the free-base octabutoxyphthalocyanine by the direct metalation with Ru3(CO)12. The first examples of catalytic activity of Ru(IV) binuclear phthalocyanines...
Three ruthenium(II) phthalocyanines functionalized at their axial positions with 4 - 12 PEG chains bearing hydroxy, amino and ether terminal groups, were synthesized and studied as PDT agents against bladder cancer cells. All three dyes displayed high singlet oxygen generation quantum yields in DMSO (Ф∆ = 0.76). The water-soluble Ru(L3)2Pc also shows high singlet oxygen quantum yields (Ф∆ = 0.48) in neat water. In vitro studies show that these complexes are accumulated in bladder cancer cells, are nontoxic PSs per se, and have high phototoxicity efficiency.
The Ru(II) sensitizers, [((HOOC)(n)-(Pc))Ru(NCS)(2)](2-) (labeled as Pc-n; n = 0-4, Pc = phthalocyanine) and [((HOOC)(n)-(TBPor))Ru(NCS)(2)](2-) (Porn; n = 0-4, TBPor = tetrabenzoporphyrin), for solar cells have been studied on their optoelectronic and redox properties using density functional theory (DFT) and time-dependent DFT. It was shown that the number of carboxylic groups bonding to tetrapyrrolic ligands (i.e. Pc and TBP or) can fine-tune electronic structures and absorption transitions of Pc-n and Por-n, but slightly change their geometries. The tetrapyrrolic macrocycles, especially in the cases peripherally substituted by carboxylic acids, are the ideal spot to accommodate excited electrons. Analyses on both atomic electron-spin density and electronic structures reveal that one-electron oxidation of Pc-n and Por-n occurs around ruthenium and -NCS moieties; in contrast, that of [(Pc)Ru(Py-COOH)(2)] (PcRuPy, Py = pyridine) was calculated to be macrocycle-based, agreeing with experimental observation. Additionally, intensities of Q absorption bands of Pc-n and Por-n have been calculated to be strongly enhanced upon increasing the carboxylic acid number. Among them, Por-4 shows intense and broad Q bands centered at 508, 546, and 617 nm, matching well with solar spectrum. In brief, the present calculated results of electronic structures, spectral features, and oxidation potentials as well as comparison with experimentally known dyes of PcRuPy and [((HOOC)(2)-(bipyridine))(2)Ru(NCS)(2)] (N3) suggest that Pc-n and Por-n, especially Por-4, would be suitable photosensitizers for dye-sensitized solar cells (DSSCs).
Here we present the synthesis and properties of quinoline-substituted zinc(II) phthalocyanine, Zn[Pc(O-QN) 4 ]. Zn[Pc(O-QN) 4 ] can function as a highly selective chemosensor against Fe3+ and Zn2+ ions, exhibiting efficient fluorescence quenching and enhancement, respectively. Various characterization techniques were employed to investigate the intermolecular interactions of Zn[Pc(O-QN) 4 ] with metal ions. A double-electron exchange and a forbidden photoinduced electron transfer behavior in Zn[Pc(O-QN) 4 ] were attributed to such opposite responses. Furthermore, by taking advantage of selectivity, we successfully employed Zn[Pc(O-QN) 4 ] to stain and record confocal fluorescence microscopy images of Chang liver cells in the presence of metal ions.
This work deals with the synthesis and photophysical study of fluorescent molecules, aiming to construct new chemical sensors for the selective detection of environmentally or biologically important metal ions. A series of fluoroionophores consisting of triazole moiety and different fluorophores was utilized to investigate the functions of triazole group in chemosensors. Our comprehensively photophysical and complexing studies of these ligands demonstrated that triazole groups could contribute as part of conjugated fluorophores, as metal binding sites or linkers. Several selective chemosensors were successively developed for the detection of Cu2+ or Hg2+. By incorporating dansyl fluorophore into calix[4]bisazacrown, a new potassium chemosensor was constructed. A sulfonate fluorescent calix[4]bisazacrown was created for the selective and ratiometric detection of Al3+ in lutidine buffer solution at pH 6.0 with a satisfying sensitivity. Finally, we aim to realize modulation of cation binding through the photoinduced charge redistribution in the excited state. Two binding motifs based on fullerene and betaine pyridinium were designed for this purpose. Preliminary results demonstrated that PET in fullerene might be not suitable but pydinium betaine hold great potential in the cation translocations.
Recently, growing attention has been paid to the sensitive determination and removal of Cu2+ because short-term exposure to high levels of Cu2+ can cause gastrointestinal disturbance and long-term exposure can cause damage to the liver and kidneys. In this paper, we herein reported a novel reusable glutathionemodified magnetic fluorescent Fe3O4@ ZnS nanosensor (MFNS) for simultaneous detection and removal of Cu2+ from contaminated water samples. The results showed that MFNS could quantificationally detect Cu2+ with high sensitivity and selectivity under a broad pH range (pH 4.6-9). The maximum sorption capacity of MFNS was calculated to be about 91 mg g(-1), which is superior to the reported reports. The removal of Cu2+ from contaminated water samples was achieved by the aggregation-induced sedimentation (AIS) strategy. Moreover, the suspended magnetic nanosensor could be removed by external magnetic field, and the potential secondary pollution was avoided.
Structurally simple, 2,2-diferrocenylpropane-based ion pair receptor 1 was synthesized and characterized by 1H NMR, 13C NMR, HRMS, elemental analyses, and single-crystal X-ray diffraction. The ion pair receptor 1 showed excellent selectivity and sensitivity towards Pb2+ with multi-channel responses: fluorescence enhancement (more than 42-fold), a notable color change from yellow to red, redox anodic shift (ΔE1/2 = 151 mV), while HSO4- promoted the fluorescence enhancement when Pb2+ or Zn2+ were bounded to the cation binding-site. 1H NMR titration and density functional theory were carried out to reveal the sensing mechanism based on photo-induced electron transfer (PET).
It is well known that photosensitizers play a vital role in the dye-sensitized solar cells (DSSCs). Understanding of their structures and photophysical properties is necessary to enhance the photoelectric conversion efficiency of DSSCs. In this work, a series of sensitizers [PcRu(RPy)(Py-COOH)] (Pc=phthalocyanine, Py=pyridine, R=COOH, ON, H, Me and OMe) as well as their one- and two-electron oxidized derivatives have been investigated using density functional theory (DFT) and time-dependent DFT. Their structural and spectroscopic properties were addressed. Full optimization demonstrates the ruthenium center exhibits octahedral geometry with six nitrogen donors. One- and two-electron oxidation slightly shortens equatorial Ru-N bond lengths relative to neutral dyes, but lengthens their axial ones. The experimentally known RuPc-1 has been calculated to evaluate performance of various functionals, basis sets, computational models of solvent effect and solvent sorts. And the TD-BLYP/SDD/PCM/Ethanol approach was used for spectral calculation in the present work. The comparison among calculated absorption spectra reveals that the neutral complexes are more suitable for photosensitizers in dye-sensitized solar cells than their oxidized derivatives. Neutral dyes were calculated to display a strong Soret absorption peak at 350 nm and a relatively weak Q band at 600 nm. They were assigned as intra-phthalocyanine pi ->pi* transition and Ru -> Py-COOH metal-to-ligand charge transfer. As these dyes anchor to semiconductor photoanode by the carboxyl of axial pyridyl group, their it pi ->pi* transition has no contribution to the subsequent electron injection. Further association with above ruthenium dyes missing absorption between 400 similar to 580 nm in visible region elucidates why DSSCs sensitized by them have such a low overall conversion efficiency of photo to electricity. Building on the present results, it is suggested to fabricate a sensitizer like [((COOH)(n)-(Pc))Ru(L)(2)], where anchoring carboxylic acids are bonded to equatorial Pc macrocycle and strong electron-donating groups are axially introduced. With this arrangement, Ru center, donating L groups and Pc macrocycle (high-lying pi occupied orbitals) all serve as electron donors, while Pc ligand (low-lying pi* unfilled orbitals) and peripheral carboxylic substituents behave as electron-accepting reservoir. This in-progress work is anticipated to design dyes that improve the conversion efficiency of DSSCs.
We report a novel synthetic approach, with good yields, for the synthesis of selective dimethylamine-substituted phthalonitriles (1-3) in the presence of triethyl phosphite and dimethylformamide at 160 oC. The peripherally-modified dimethylamine substituted Zn(II)phthalocyanines (ZnPc1-3) with varied number and position of dimethylamine groups were prepared for a systematic investigation on the effect of the substituents on their electronic and spectroscopic properties. Compounds show strong aggregation behaviour in methanol and this behaviour decreasing with the increase of the alkyl chain of the alcohol solvents (i.e., from methanol to octanol). The fluorescence quantum yields of ZnPc1-3 showed an excellent correlation with the extent of the molecular aggregation. The versatility of the ZnPc1-5 compounds possessing both electron donating and electron withdrawing substituents at their periphery is investigated towards the detection of nitroaromatic compounds (NACs) in solution and in the vapour phase. It was found that ZnPc1-5 exhibit high selectivity towards trinitrophenol (TNP). A good linearity of the fluorescence detection using ZnPc3 as the fluorescent probe was observed in the concentration range of 50×10−6–450×10−6 M in chloroform, with a detection limit (LOD) of 11±2 ppm. Stern-Volmer (SV) and DFT studies reveal that the fluorescence quenching behaviour occurs through photo-induced electron transfer from the excited state of Zn(II)phthalocyanine to TNP with static quenching behaviour occurring in a predominant fashion. The formation of honeycomb-type pores of ZnPc3 thin film promotes high selectivity and accessibility to TNP vapours (7.7x10-3 ppb).
A new rhodamine-based sensor 1 was designed and synthesized by incorporating rhodamine B and benzimidazole moieties Sensor 1 exhibits high selectivity and sensitivity to Cu2+ in CH3CN-water solution (HEPES buffer, pH = 7 0) with an obvious color change from colorless to pink Other metal ions such as Hg2+, Ag+, Pb2+, Sr2+, Ba2+, Cd2+, Ni2+, Co2+, Fe2+, Mn2+, Cu2+, zn(2+), Ce2+, Mg2+, K+ and Na+ had no such color change and have no significant Influence on Cu2+ recognition process The interaction of Cu2+ and sensor 1 was proven to adopt a 1 1 binding stoichiometry and the recognition process is reversible
A new dinuclear Ru(II) polypyridyl complex, [(bpy)2 Ru(H2 bpip)Ru(bpy)2 ](4+) (RuH2 bpip, bpy=2,2-bipyridine, H2 bpip=2,6-pyridyl(imidazo[4,5-f][1,10]phenanthroline), was developed to act as a one- and two-photon luminescent probe for biological Cu(2+) detection. This Ru(II) complex shows a significant two-photon absorption cross section (400 GM) and displays a remarkable one- and two-photon luminescence switch in the presence of Cu(2+) ions. Importantly, RuH2 bpip can selectively recognise Cu(2+) in aqueous media in the presence of other abundant cellular cations (such as Na(+) , K(+) , Mg(2+) , and Ca(2+) ), trace metal ions in organisms (such as Zn(2+) , Ag(+) , Fe(3+) , Fe(2+) , Ni(2+) , Mn(2+) , and Co(2+) ), prevalent toxic metal ions in the environment (such as Cd(2+) , Hg(2+) , and Cr(3+) ), and amino acids, with high sensitivity (detection limit≤3.33×10(-8) M) and a rapid response time (≤15 s). The biological applications of RuH2 bpip were also evaluated and it was found to exhibit low cytotoxicity, good water solubility, and membrane permeability; RuH2 bpip was, therefore, employed as a sensing probe for the detection of Cu(2+) in living cells and zebrafish.
Carboxylic acid–diamine-based Cu chromogenic sensors (3 and 4) exhibited colour switching from red to blue with good sensitivity and selectivity towards Cu among other physiologically important alkali, alkaline earth and heavy metal ions. This colour-switching phenomenon arises due to selective deprotonation of aryl amine NH by Cu. Significantly, chemosensor 3 (λmax 492 nm) shows multiple modes of complexation towards Cu. It is very much evident from the appearance of blue colour (λmax 615 nm) at pH >7.0 and yellow colour (λmax 465 nm) at pH
Two 4,5-disubstituted-1,8-naphthalimide derivatives 1 and 2 were synthesized as ratiometric fluorescent and colorimetric sensors for Cu2+, respectively. In 100% aqueous solutions of 1, the presence of Cu2+ induces a strong and increasing fluorescent emission centered at 478nm at the expense of the fluorescent emission of 1 centered at 534nm. Compound 2 senses Cu2+ by means of a colorimetric (primrose yellow to pink) method with a thorough quench in emission attributed to the deprotonation of the secondary amine conjugated to the naphthalimide fluorophore. 1-Cu2+ and 2-Cu2+ sense cyanide in ratiometric way via colorimetric and fluorescent changes.
Merocyanine dye 1 was prepared as an effective colorimetric and fluorescent chemosensor for copper ions in aqueous media, and displays a significant color change from reddish-purple to yellow with a large blue shift of 94 nm in its absorption spectrum in the presence of one equivalent of copper. As an on-off fluorescent sensor, it is feasible to detect copper ions in living cells due to its good cell permeability and high solubility under physiological conditions. © 2010 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Fully conjugated metallosupramolecular self-assembled multilayer films were controllably fabricated based on bibenzonitril-phthalocyaninato ruthenium(II) (BBPR) and 4,4'-bipyridine (BP) via axially coordination interaction between ruthenium ions and the pyridine groups on the modified substrates. The substrates were firstly functionalized by 4-(pyridine-4-ylethynyl)benzenic diazonium salt (PBD) through photodecomposition of diazonium group under UV irradiation. As a result, the pyridine-containing functional groups were vertically, and covalently anchored onto the surface of substrate and got a stable monolayer. Soluble ruthenium phthalocyanine, axially coordinated by labile benzonitrile groups, was used to fabricate the layer-by-layer self-assembled films with 4,4'-bipyridine through ligand-exchanging reaction between benzonitrile and pyridine in each self-assembled cycle. The UV-vis analysis results demonstrated the successful fabrication of bi(4,4'-bipyridine)phthalocyaninato ruthenium(II) (BPPR) metallosupramolecular ultrathin films with definite structures on PBD-modified substrate. Under illumination, the BPPR self-assembled multilayer films displayed a quick response to light. The maximum current density reached 120 nA/cm2 at six bilayers. The Eg, HOMO, and LUMO of the six-bilayer were quantitatively measured to be 1.68, -5.29, and -3.61 eV, respectively. This strategy supplies a facile method to get full-conjugated metallosupramolecules and a platform for developing higher performance solar cell from the point of adjusting dye aggregate state structure.
A simple epoxy-based oligomer 1 containing naphthylazobenzene-appended dithia-aza moieties was prepared. In UV–vis measurements, the proposed oligomer showed the ion-sensing ability to Hg2+ and Cu2+ ions. The discrimination between two differently responding Hg2+ and Cu2+ ions was also realised from ‘ON–OFF’ type fluorescence responses of 1.
A series of six 2,2′-bipyridine-3,3′-diols with different substituents have been synthesized and characterized. The designed ligands show fluorescence in the visible part of the spectra, but only the luminescence of the less sterically hindered molecules is quenched in the presence of Cu2+ ions. Selectivity and sensitivity of the chemosensors have been tested by absorption and luminescence spectroscopy in aqueous solutions, with a dynamic working range of 0.7–30 μM and a limit of detection of 0.04 ppm (mg L–1).
This overview focuses on the design and preparation of phthalocyanines (Pcs) and covers both fundamental synthetic approaches
and more applied research. Thus, different topics including, e.g., the preparation of conjugated assemblies using Pcs as synthetic
building blocks, the supramolecular organization of appropriately featured Pc-molecules, and the incorporation of Pcs into
dendrimers and polymers, are discussed in this chapter. The second part of the review has been devoted to more technological
aspects of these compounds covering Pc-based nanostructures and Pcs as active components of functional devices.
KeywordsFunctional phthalocyanines-Macromolecular structures-Multicomponent assemblies-Nanostructuration-Supramolecular organization
The development of efficient red sensitizer dyes is essential for the optimization of dye-sensitized photoelectrochemical solar cells. Ru-phthalocyanines are good candidates because they show high absorbance in the red while their axial ligands hinder the formation of aggregates, a recurrent problem among phthalocyanine dyes. In this paper, we present the photophysics and photovoltaic device performance for a series of novel Ru-phthalocyanines. We focus in particular upon the origin of the enhancement in device performance observed in the presence of two additives, Li+ and chenodeoxycholic acid. The addition of Li+ lowers the conduction band edge of the TiO2 semiconductor leading to a higher electron injection yield and a higher photocurrent in the device. The increases in injection yield and photocurrent are large for these sensitizers, compared to the widely studied ruthenium bipyridyl dye N719, due to the relatively slow injection dynamics, emphasizing the importance of injection yield in limiting device performance for this Ru-phthalocyanine dye series. Of particular interest is the effect of chenodeoxycholic acid. This coadsorbent dramatically enhances the photocurrent of the studied devices without lowering the photovoltage. Unlike previous studies, in this case the photocurrent rise can not be attributed to an increment in the electron injection yield due to the effect of the coadsorbent hindering the formation of dye aggregates. Photophysical measurements instead show that the slower recombination of dye cations with the TiO2 electrons and faster regeneration of the dye cations by the electrolyte are the reasons for the enhanced photocurrent.
Novel triazaporphyrins were synthesized using 1,9-dibromodipyrromethene as a key starting material. These triazaporphyrins exhibit comparatively intense Soret and Q bands in the UV/vis region due to their hybrid properties between porphyrins and phthalocyanines.
Phthalocyanine (Pc) dimers connected through trans-platinum(II) diacetylide linkers have been prepared by reaction of the corresponding ethynylphthalocyanines with trans-bis(triethylphosphine)platinum(II) chloride. Special emphasis was placed on the analysis of the ground- and excited-state features of these compounds in relation to butadiyne-bridged Pc dimers and the corresponding monomers. Both Zn(II)-containing Pc dimers exhibit long-lived triplet excited states. The insertion of σ-bonded trans-platinum(II) diacetylide spacers decoupled the two Pc groups and led to an appreciable acceleration (by a factor of up to 10) of the radiative and nonradiative decay rate of the singlet and triplet excited states.
A series of new metallodendrimers built around a ruthenium phthalocyanine core has been prepared. Employing a convergent synthetic strategy, pyridine-containing ligands were prepared and then assembled onto the ruthenium phthalocyanine through axial ligand coordination. The growing shell of oligoethylene glycol chains surrounding the lipophilic core allows solubilisation in water. Photophysical studies show that all the metallodendrimers are strongly phosphorescent and the deactivation pathway of their triplet state depends on the medium in which the compounds are dissolved. On one hand, quenching of the triplet state by the dendritic shell is observed and found to be substantially enhanced in aqueous media. On the other, the dendrimer shields the phthalocyanine from oxygen. This notwithstanding, the phthalocyanines are able to generate singlet oxygen in less polar environments such as in CHCl(3) or THF solution, while in water the generation of singlet oxygen is almost completely switched off.
N,N'-((5,5'-(quinoxaline-2,3-diyl)bis(1H-pyrrole-5,2-diyl))bis(methanylylidene))bis(4-methoxyaniline) 4 and N,N'-((5,5'-(quinoxaline-2,3-diyl)-bis(1H-pyrrole-5,2-diyl))bis(methanylylidene))dianiline 5 have been prepared and structurally characterized. The X-ray crystal structures of compounds 4 and 4a have been determined. These compounds displayed good sensitivity toward transition metal ions with Cd(II), Zn(II) turn-on and Cu(II), Hg(II) turn-off in fluorescence. It is an elegant example of on/off behavior like a lamp. When Cd(II) or Zn(II) is added into compounds 4 or 5, the lamp will switch on, and then when Cu(II) or Hg(II) is added into the mixture, the lamp will switch off. The binding properties of 4 and 5 for cations were examined by fluorescence spectroscopy. The fluorescence data and crystal structure indicate that a 1:1 stoichiometry complex is formed between compound 4 (or 5) and metal ions, and the binding affinity is very high. The recognition mechanism between compound 4 (or 5) and metal ion was discussed based on the their chemical constructions and the CHEF/CHEQ effect when they interacted with each other.
A minimalist squaramide-based chemodosimeter for Cu(2+) is described. Upon selective chelation to 2, Cu(2+) induces the formation of a highly colored zwitterionic radical, which is kinetically stable for hours. The presence of a radical is confirmed by EPR and ESI-MS. It is then possible to use reagent 2 for visual and selective sensing of Cu(2+) at neutral pH.
A Cu(2+)-specific colorimetric sensor 1, which is stabilized by an intramolecular hydrogen bonding, was designed and developed. The color of 1 changes from purple to blue on addition of 1.0 muM Cu(2+) in aqueous buffer solution, which can be detected by the naked eye. The analytical detection limit for Cu(2+) by the naked eye is as low as 1.0 muM. The stoichiometry for 1 and Cu(2+) in complex is 2:1 in aqueous solution.
The convergent synthesis, electrochemical characterization, and photophysical studies of phthalocyanine-fullerene hybrids 3-5 bearing an orthogonal geometry (Chart ) are reported. These donor-acceptor arrays have been assembled through metal coordination of linear fullerene mono- and bispyridyl ligands to ruthenium(II) phthalocyanines. The hybrid [Ru(CO)(C(60)Py)Pc] (3) and the triad [Ru(2)(CO)(2)(C(60)Py(2))Pc(2)] (5) were prepared by treatment of the phthalocyanine 6 with the mono- and hexakis-substituted C(60)-pyridyl ligands 1 and 2, respectively. The triad [Ru(C(60)Py)(2)Pc] (4) was prepared in a similar manner from the monosubstituted C(60)-pyridyl ligand 1 and the phthalocyanine precursor 7. The simplicity of this versatile synthetic approach allows to determine the influence of the donor and acceptor ratio in the radical ion pair state lifetime. The chemical, electrochemical, and photophysical characterization of the phthalocyanine-fullerene hybrids 3-5 was conducted using (1)H and (13)C NMR, UV/vis, and IR spectroscopies, as well as mass spectrometry, cyclic voltammetry, femtosecond transient absorption studies, and nanosecond laser flash photolysis experiments. Arrays 3-5 exhibit electronic coupling between the two electroactive components in the ground state, which is modulated by the axial CO and 4-pyridylfulleropyrrolidine ligands. With respect to the excited state, we have demonstrated that RuPc/C(60) electron donor-acceptor hybrids are a versatile platform to fine-tune the outcome and dynamics of charge transfer processes. The use of ruthenium(II) phthalocyanines instead of the corresponding zinc(II) complexes allows the suppression of energy wasting and unwanted charge recombination, affording radical ion pair state lifetimes on the order of hundreds of nanoseconds for the C(60)-monoadduct-based complexes 3 and 4. For the hexakis-substituted C(60) unit 2, the reduction potential is shifted cathodically, thus raising the radical ion pair state energy. However, the location of the RuPc triplet excited state is not high enough, and still offers a rapid deactivation of the radical ion pair state.
Within the present work, two series of novel ruthenium(II) phthalocyanine (RuPc) complexes with one [RuPcCOPy-nT] or two [RuPc(Py-nT)(2)] dendritic oligothiophene (DOT) ligands in the axial positions are reported. The ability of Ru(II) for axial coordination in RuPcs allowed the attachment of the Pc through the metal site to the DOT-ligands bearing pyridine at the core position of the dendrons. These extended pyridine functionalized conjugated DOT-ligands (Py-nT) were chosen to cover the spectral window between 380 and 550 nm, where the RuPc does not exhibit a strong absorption, in order to improve the light-absorption of these complexes and hence enhance the efficiency of the corresponding solar cells. Good efficiencies of up to 1.6% have been achieved when blended together with a fullerene acceptor in solution-processed photovoltaic devices, providing by far the best phthalocyanine-based bulk heterojunction solar cells reported to-date.
The application of ruthenium phthalocyanine complexes as sensitizing dyes in dye-sensitized solar cells (DSCs) is explored. Four monomeric complexes are reported which vary in peripheral substitution and axial ligand anchoring groups. Sensitizing dyes containing two ruthenium centers are also presented. These dyads, which contain ruthenium phthalocyanine and bipyridyl chromophores, were prepared using a protection/deprotection strategy that allows for convenient purification. DSCs fabricated using the phthalocyanine complexes and dyads were less efficient than those incorporating a standard DSC dye. However, on the basis of the number of molecules bound to the TiO(2) electrode surfaces, several of the new complexes were more efficient at photocurrent generation. The results highlight the importance of molecular size, and thus the dye coverage of the electrode surface in the design of new sensitizing dyes.
A Cu2+-specific colorimetric sensor of a 1,8-naphthalimide chromophore integrated with a 2-aminodiphenylamine (2-adpa)-based receptor was designed and synthesized. Sensor had high selectivity and sensitivity for Cu2+ in neutral aqueous buffer solution. The analytical detection limit (ADL) was 3.0 x 10(-7) M. Based on the Cu2+-induced deprotonation of the diarylamino "NH" moiety, the coordination mode was proposed with 1:1 stoichiometry between and Cu2+. These results opened up possibilities for the construction of novel colorimetric sensors with a red-shift absorption in a D-pi-A system.
We have described a new compound (trans-[RuCl([15]aneN(4))NO](2+)), which in vitro releases NO by the action of a reducing agent such as catecholamines. We investigated the effect of this NO donor in lowering the mean arterial pressure (MAP) in severe and moderate renal hypertensive 2K-1C rats. MAP was measured before and after intravenous in bolus injection of the compound in conscious 2K-1C and normotensive (2K) rats. In the hypertensive rats (basal 196.70+/-8.70mmHg, n=5), the MAP was reduced in -34.25+/-13.50mmHg (P<0.05) 6h after administration of 10mmol/L/Kg of the compound in bolus. In normotensive rats the compound had no effect. We have also studied the effect of the injection of 0.1mmol/L/Kg in normotensive (basal 118.20+/-11.25mmHg, n=4), moderate (basal 160.90+/-2.30mmHg, n=6), and severe hypertensive rats (basal 202.46+/-16.74 mmHg, n=6). The compound at the dose of 0.1mmol/L/Kg did not have effect (P>0.05) on MAP of normotensive and moderate hypertensive rats. However, in the severe hypertensive rats (basal 202.46+/-16.70mmHg, n=6) there was a significant reduction on the MAP of -28.64+/-12.45mmHg. The NO donor reduced the MAP of all hypertensive rats in the dose of 10mmol/L/Kg and in the severe hypertensive rats at the dose of 0.1mmol/L/Kg. The compound was not cytotoxic to the rat aortic vascular smooth muscle cells in the concentration of 0.1mmol/L/Kg that produced the maximum relaxation.
Vascular endothelium generates nitric oxide (NO) in large vessels and induces relaxation of vascular smooth muscle cells (VSMC). The aim of this study was to evaluate the contribution of NO produced in the endothelial cells (EC) to the relaxation induced by the Ca2+ ionophore A23187 and whether this relaxation is impaired in renal hypertensive (2K-1C) rat arteries. Concentration-effect curves for A23187 were constructed in intact endothelium isolated carotid rings from 2K-1C and normotensive (2K) in the absence or in the presence of the extracellular NO scavenger haemoglobin or inhibitors of NO-synthase (NOS, L-NOARG), guanylyl-cyclase (GC, ODQ). In carotid rings loaded with Fluo-3AM, both EC and VSMC were simultaneously imaged by a confocal microscope and [Ca2+]c was derived from fluorescence intensities (IF). The maximal relaxation (ME) induced by A23187 was lower in 2K-1C than in 2K arteries. A23187-induced relaxation was abolished by haemoglobin and L-NOARG in both groups. ODQ reduced the ME to A23187 in 2K and abolished its relaxation in 2K-1C. A23187 increased [Ca2+]c in a similar way in 2K and 2K-1C EC, and decreased [Ca2+]c in VSMC, which effect was higher in 2K than in 2K-1C arteries. L-NOARG inhibited the effect of A23187 in VSMC from 2K and abolished it in 2K-1C rats. On the other hand, L-NOARG did not modify the effect of A23187 in EC from 2K and 2K-1C rats. The basal content of cGMP was higher in 2K than in 2K-1C arterial rings that was similarly increased by A23187. In conclusion, the Ca2+ ionophore A23187 increases Ca2+, activates NOS and NO production in the EC activating GC in VSMC and [Ca2+]c decrease. All these effects are higher in 2K, which contribute to the impaired relaxation to A23187 in 2K-1C rat arteries.
A series of N-acylhydrazones were synthesised and found to be "turn-on" fluorescent chemodosimeters for Cu(2+). Among the tested transition metal ions such as Cu(2+), Pb(2+), Zn(2+), Cd(2+), Hg(2+), and Ni(2+), a prominent fluorescence enhancement of up to 1000-fold was only observed for Cu(2+) in acetonitrile (CH(3)CN). This was indicated by an onset of unprecedented structured emission. Detailed experiments established that the highly Cu(2+) selective fluorescence enhancement resulted from an oxidative cyclization by Cu(2+)of the originally nonfluorescent N-acylhydrazones into highly fluorescent rigid 1,3,4-oxadiazoles, n-dope type blocks in optoelectronic materials. The chemodosimeters can be applied to sense Cu(2+) at nM levels in CH(3)CN and sub-microM levels in neutral aqueous environments, despite a slower response in the latter case. It is expected that these redox-based chemodosimeters might be of general applicability.
This paper examines the preparation of tailor-made azaporphyrins and analogues exhibiting their Q-bands in several particular and predetermined regions of the electromagnetic spectrum. The applications of phthalocyanines, the possibility of preparing novel related porphyrinoids with different colour properties and, consequently, new emerging applications, are discussed.
Homogeneous electron transfer reactions of the Cu(II) complexes of 5,10,15,20-tetraphenylporphyrin (TPP) and 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) with various oxidizing reagents were spectrophotometrically investigated in acetonitrile. The reaction products were confirmed to be the pi-cation radicals of the corresponding Cu(II)-porphyrin complexes on the basis of the electronic spectra and the redox potentials of the complexes. The rate of the electron transfer reaction between the Cu(II)-porphyrin complex and solvated Cu(2+) was determined as a function of the water concentration under the pseudo first-order conditions where Cu(2+) is in large excess over the Cu(II)-porphyrin complex. The decrease in the pseudo first-order rate constant with increasing the water concentration was attributed to the stepwise displacement of acetonitrile in [Cu(AN)(6)](2+)(AN = acetonitrile) by water, and it was concluded that only the Cu(2+) species fully solvated by acetonitrile, [Cu(AN)(6)](2+), possesses sufficiently high redox potential for the oxidation of Cu(ii)-OEP and Cu(ii)-TPP. The reactions of the Cu(II)-porphyrin complexes with other oxidizing reagents such as [Ni(tacn)(2)](3+)(tacn = 1,4,7-triazacyclononane) and [Ru(bpy)(3)](3+)(bpy = 2,2'-bipyridine) were too fast to be followed by a conventional stopped-flow technique. Marcus cross relation for the outer-sphere electron transfer reaction was used to estimate the rate constants of the electron self-exchange reaction between Cu(II)-porphyrin and its pi-cation radical: log(k/M(-1) s(-1))= 9.5 +/- 0.5 for TPP and log(k/M(-1) s(-1))= 11.1 +/- 0.5 for OEP at 25.0 degrees C. Such large electron self-exchange rate constants are typical for the porphyrin-centered redox reactions for which very small inner- and outer-sphere reorganization energies are required.
The electrochemistry and UV-vis spectral properties of neutral and electroreduced Al(III) phthalocyanine, (Pc)AlCl, were characterized in four different nonaqueous solvents (THF, DMSO, DMF, and pyridine) containing tetra-n-butylammonium perchlorate, as well as in THF containing 0.4 M TBAP and the more strongly coordinating Cl-, F-, OH-, or CN- anions added to solution in the form of a tetra-n-butylammonium salt. The initial phthalocyanine added to solution is represented as (Pc)AlCl, but the actual electroactive form of the compound varied as a function of both the solvent and type or number of bound anionic axial ligands. An uncharged (Pc)AlCl(THF) or (Pc)Al(CN)(THF) complex is present in THF solutions containing 0.4 M TBAP and excess Cl- or CN-, while transient mu-oxo dimers are spectroscopically observed upon addition of OH- or F- to (Pc)AlCl(THF) in THF followed by the ultimate formation of stable six-coordinate anionic species represented as [(Pc)Al(OH)2]- or [(Pc)AlF2]-. Each phthalocyanine undergoes three reversible one-electron additions at the conjugated Pc macrocycle within the negative potential limit of the solvent, and the UV-vis spectral changes obtained during the first two reductions were recorded in a thin-layer cell to evaluate the prevailing electron-transfer mechanisms.
Phthalocyanines are versatile building blocks for fabricating materials at the nanometer scale. These colored macrocycles exhibit fascinating physical properties which arise from their delocalized pi-electronic structure. This article describes why these molecules are targets for different scientific purposes and technological applications.
A new dansyl derived fluorescent sensor for Cu(II) ions (1) has been isolated by four-step organic synthesis with a good yield and characterized by NMR- and ESI-MS methods. UV–Vis and fluorescent titrations of 1 with Cu(II), Co(II), Zn(II), Ni(II), Ca(II) and Mg(II) salts were performed. 1 forms a 1:1 stable complex in solution (1 × 10−6 M) with Cu(II) and does not form such complex with other metals. 1 has been attached to a CPG 1000/100 resin. The fluorescence images of CPG 1000/100 resin with 1 have shown strong fluorescence and complete absence of it in the presence of Cu(II) anions.
Azo 8-hydroxyquinoline benzoate (2) was synthesized and studied to detect metal ions. Distinct color change was found for compound 2 in the presence of transition metal ions Hg2+ or Cu2+ in CH3CN, respectively, which makes it possible for distinguishing Hg2+ and Cu2+ from other metal ions by the ‘naked eye’.
Complementary syntheses of 1,4,8,11,15,18,22,25-octakis(alkyl) substituted ruthenium phthalocyanines, in which either one or two axial ligands can be added, are described. Their utility in the preparation of further (pyridyl) ligated derivatives has been shown to be straightforward. The chemistry is sufficiently robust and efficient to permit elaborate, supramolecular complexes to be prepared, as demonstrated by the synthesis of porphyrin-phthalocyanine multichromophore arrays. (c) 2005 Elsevier Ltd. All rights reserved.
Upon Q-band excitation (irradiation wavelength > 580 nm) ruthenium(II) phthalocyanine complexes can be quantitatively photooxidized to stable φ- cation radical species. The photooxidation can be carried out at either room temperature using CH2Cl2 solutions containing CBr4 as an 'irreversible' electron acceptor, or in low-temperature (79 K) 2-methyl- tetrahydrofurane solutions containing 2,3-dichloro- 5,6-dicyanobenzoquinone as a 'reversible' acceptor. Absorption and magnetic circular dichroism (MCD) spectra indicate that there are two major, resolved transitions in the visible region, one at 510 nm and the other at 700 nm. The MCD spectra of the transition at 510 nm shows that it is non-degenerate, while the transition at 700 nm is seen to be degenerate in the case of photooxidized Ru(II)Pc(−2)(CO)DMF at room temperature.
The electrochromic properties observed in manganese and chromium phthalocyanine thin films are reported. Schemes are proposed to explain the chemistry involved in the electrochromic changes. Both chromium and manganese are shown to undergo changes in their valence states during oxidation and reduction of the phthalocyanine films. The phthalocyanine rings also undergo oxidation and reduction with cycling between reduced and oxidised states but the latter were not stable. Although changes in colour were observed in both materials on oxidation, the films degraded and so the results were not useful. The films have been found to cycle reversibly a few thousand times between neutral and reduced states. However, their cycling properties and colour range are greatly inferior to the metal bisphthalocyanine films.
Copper(I) solvation in mixed solvent systems containing acetonitrile (AN) and co-solvents water (W), methanol (ME), dimethylformamide (DMF), trimethyl phosphate (TMPA), trimethyl phosphite (TMP) or pyridine (PY) have been studied using 63Cu, 65Cu and 31P NMR. Evidence for preferential solvation by AN is given for the first four systems whereas the latter two are characterized by strong preferential solvation of the copper(I) ion by the co-solvent. From the linewidths of the 63Cu and 65Cu signals the rotational correlation times τR of the solvates Cu(AN)+4 and Cu(PY)+4 have been determined.
A supramolecular Pc–C60 dyad with pseudorotaxane-like geometry has been assembled in solution by the threading of a dibenzylammonium unit attached to a fullerene through the crown ether of an unsymmetrically substituted phthalocyanine, which contains a DB24C8 moiety. Spectroscopic data as well as electrochemical studies suggest a conformation for the complex in which the two bulky subunits are far apart from each other, thus preventing electronic interactions between both electroactive subunits.
The electrochromic behaviour of titanyl phthalocyanine [Ti(O)(pc)] and vanadyl phthalocyanine [V(O)(pc)] thin films are reported. These materials manifest a reversible electrochromic change when reduced, but upon oxidation they show evidence of immediate destructive breakdown. The behaviour of the films is discussed in relation to the α- and β-phase structures of the films. It is found that the phase of [Ti(O)(pc)] changes during the electrochromic process owing to ion incorporation. This is the first report of an electrochromically induced phase change in metal phthalocyanine materials. The structure of the phase present in a metal phthalocyanine material is found to dictate whether or not it is electrochromic. If the structure is too closely packed to allow ion penetration, it will not be electrochromic. The implications of the irreversible oxidations are discussed in relation to the behaviour of metal bisphthalocyanine electrochromic materials.
Hexaphyrin(1.0.1.0.0.0) (isoamethyrin) undergoes a significant color change in the presence of UO22+, PuO22+ and NpO22+. The complexation of the first of these dioxo actinide cations was studied in semi-quantitative fashion in 1:1 MeOH-CH2Cl2. Under these conditions, the detection limit for UO22+ was found to be ca. 5.8 ppm by naked eye monitoring and < 28 ppb by UV-vis spectroscopy. Isoamethyrin does not undergo a color change in the presence of most transition metals or when exposed to Gd(III). Isoamethyrin thus constitutes an attractive altemative to 2,2'(1,8-dihydroxy-3,6-disulfonaphthylene-2,7-bisazo)-bisbenzenarsonic acid (AzIII) and 2-(5-bromo2-pyridylazo)-5-(diethylamino)phenol (BrPADAP), systems currently used as actinide cation sensors.
Cyclooligomeric phthalocyanines with the special feature of having a dehydroannulene core are described. Compounds 4a,b and 5a,b were prepared by an oxidative coupling mediated by copper from the corresponding diethynyl unsymmetrically substituted phthalocyanines 8a,b, which are easily accessible from the corresponding diiodo compounds 6a,b by a palladium−copper-catalyzed coupling. Appropriate conditions to selectively form cyclodimers and cyclotrimers using Glaser and Eglinton methodologies have been attempted. In this way, two compounds, 4a and 5b, each representative of a kind of oligomers, could be appropriately isolated and characterized by MALDI-MS. The UV−vis spectra of compounds 4a and 5b show a split Q-band shifted to the red with respect to the corresponding precursor 8a,b. This can be interpreted, in light of previous results, as a consequence of intramolecular electronic coupling between the Pc subunits. Extensive formation of aggregates in chloroform can be also inferred from the spectra. No significant differences could be observed in the spectra by comparison with that of the open-chain analogue 11, most probably due to a saturation phenomenon of the optical properties already pointed out in the literature for other alkynyl-linked open-chain dimers.
The synthesis and photoproperties of six new metal 1,4,8,11,15,18,22,25-octabutoxyphthalocyanines and photoproperties of the known analogous Zn and metal-free phthalocyanines are described. The new compounds are AIPc(OBu)8OSiEt3, GaPc(OBu)8OSiEt3, GePc(OBu)8(OSiEt3)2, SnPc(OBu)8(OSiEt3)2, RuPc(OBu)8(py)2, and PdPc(OBu)8 (where Pc(OBu)8 represents the octabutoxyphthalocyanine ligand). Benzene-d6 solutions of all eight of the compounds give NMR spectra showing large ring-current effects. Benzene solutions of the compounds give visible spectra with absorption maxima in the 688-779-nm range having extinction coefficients between 1.0 × 105 and 2.2 × 105 M-1cm-1. The triplet-state properties of the phthalocyanines in benzene solutions have been measured by laser flash photolysis. The triplet states have absorption maxima in the 550-640-nm range, quantum yields in the 0.1-0.9 range, and lifetime when the solutions are deaerated in the 0.5-150-μs range. The rate constants for energy transfer from the triplet states of the compounds to O2 are between 1.3 × 108 and 2.8 × 109 M-1 s-1. Analysis of kinetic data pertaining to the photogeneration of O2 (1Δg) by the main-group compounds shows that the energy gap between their singlet (S1) and triplet (T1) states is 14.9 ± 0.3 kcal/mol. Relationships between the photoproperties of the metal complexes and the position in the periodic chart of the metals they contain are apparent.
An extensive analysis of the optical absorption and magnetic circular dichroism (MCD) spectra of the anion radical of zinc phthalocyanine ( [ (ZnPc(-3)]-) is described. Novel photochemical formation of the ring-reduced [ZnPc(-3)]- from (hydrazine)ZnIIPc(-2) is reported for reactions carried out at room temperature using visible-wavelength
light and hydrazine as the electron donor. Absorption and MCD spectra of the radical anion species have been obtained at both room and cryogenic temperatures. Phosphorescence and fluorescence lifetime studies of ZnPc(-2) show that
the photoexcited (hydrazine)ZnPc(-2) complex reacts via the triplet state to form the ring reduced anion radical, [ ZnPc(-3)]-. The complete lack of temperature dependence assignable to orbital degeneracies in the low-temperature MCD spectrum shows conclusively that the 2Eg ground state of [ZnPc(-3)]- is split into nondegenerate components at least 800 cm-1 apart. The ground and excited states are completely nondegenerate. It is proposed that the coupled effects of the loss of aromaticity with the addition of the 19th pi-electron, Jahn-Teller distortion, and nonsymmetric solvation of the ring lead to a change in molecular geometry from D4h of ZnPc(-2) to C2, for [ZnPc(-3)]-. The first complete assignment of the optical spectrum of any porphyrin or phthalocyanine anion radical is proposed on the basis of a 2B1 ground state and supported by results from extensive deconvolution calculations. Comparison between the absorption and MCD spectral data indicated that a significant fraction of the spectral intensity observed at room
temperature can be assigned as “hot” bands. The hot bands, which are much more pronounced in the spectral data of [ZnPc(-3)]- than in the spectral data of the parent ZnPc(-2), are associated with interactions between the solvent, the Pc(-3) ring, andvibronic bands associated with the split ground state. A detailed study of the temperature dependence of the absorption and MCD spectra showed that meaningful spectral deconvolution calculations could only be carried out on spectra obtained from vitrified solutions of [ZnPc(-3)]- at cryogenic temperatures. Bandwidths calculated to fit the absorption spectrum increase in magnitude as a function of the transition energy from 10 000 to 33 000 cm-1, which allows the classification of sets of bands to one of five major electronic transitions, namely, Q between 750 and 1000 nm, n - pi* between 580 and 750 nm, pi* - pi* between 430 and 650 nm, B1 and B2 between 300 and 450 nm.
Radical phthalocyanine(1-) complexes of chromium(III), iron(III), cobalt(III), and zinc(II) are reported and characterized by electronic and vibrational spectroscopy, magnetism, electron spin resonance, and Mössbauer spectroscopy and through oxidative titrations. Further elucidation of the reaction of iron(II) and, of cobalt(II) phthalocyanine with the hydrohalic acids is presented. It is suggested that most of the previously reported manganese(III) phthalocyanine derivatives are five-coordinate. A survey of the first-row transition metal phthalocyanines reveals that only the above-mentioned metal ions will form radical phthalocyanine species under the conditions used.
Reduction of metal phthalocyanines with sodium in tetrahydrofuran (or electrochemically at a mercury pool or platinum cathode) produces a series of negative ions, corresponding to the stepwise addition of electrons. The complexes with Zn(II), Ni(II), Fe(II), Mn(II), Mg(II), and AlIIICl form four distinct reduction stages, but for CoIIPc five reduction steps are found. The electronic absorption spectra are reported and used to discuss the electronic structures of the metal phthalocyanine negative ions. The spectroscopic observations indicate that all complexes, with the exception of CoIIPc and FeIIPc give reduced species in which the additional electrons are confined essentially to the ring eg orbital. Reduction of CoIIPc and FeIIPc and possibly also MnIIPc appears to involve electron addition to both ligand (eg) and metal orbitals.
The oxidation and reduction of metal phthalocyanines give rise to at least six oxidation states whose electronic spectra are rationalized in some depth in terms of SCF energies and Coulomb and exchange integrals. It is shown that a single set of parameters can reproduce the Q-band energies moderately well. Further, this same set of energies can reproduce differences in electrochemical potentials observed within this redox set. The pattern of variation in the Q-band energies (and in their number) now provides a means for identifying whether it is the metal or the phthalocyanine ligand that is reduced upon addition of an electron to the system.
The first synthesis of pure tert-butyl-substituted (phthalocyaninato)- and (2,3-naphthalocyaninato)ruthenium [(tBu)4-MacRu] by thermal decomposition of (tBu)4MacRu(L)2 (L = 3-chloropyridine, ammonia) is described. The compounds were characterized by UV/Vis, IR, and NMR measurements.
The synthesis of the octasubstituted phthalocyanine 1, highly soluble in organic solvents, is described. Its aggregation properties in different solvents and in the presence of alkaline, alkaline earth, and ammonium salts are studied.
A highly sensitive, selective colorimetric and fluorometric mol. probe based on a subphthalocyanine dye was developed for cyanide-anion detn. in aq. soln. Also a carboxysubphthalocyanine deriv. can be covalently anchored to transparent mesoporous nanocryst. high-surface-area metal oxide films to detect low concns. of cyanide anion in pure H2O with no interference from other anionic or cationic species. [on SciFinder (R)]
A latest homogeneous assay method for detecting Cu2+ ions based on the modulation of photoluminescent quenching efficiency between the perylene bisimide chromophore and gold nanoparticles (AuNPs), was demonstrated. To obtain the modulation of photoluminscent quenching of the DPPCA by AuNPs, a transmission electron microscopy (TEM) analysis of AuNPs was performed. TEM measurements indicated the aggregate formation of DPPCA-AuNPs colloids due to complexation interactions between the pyridine and Au nanoparticles. The result shows that gold nanoparticles can act as promising active materials for applications in optical sensors.
The ruthenium complexes with tetra-15-crown-5-phthalocyanine and various axial ligands were synthesized and characterized by spectroscopy. A method for the synthesis of bisaxially coordinated ruthenium(ii) tetra-15-crown-5-phthalocyaninates with the N-donor ligands (R4Pc)Ru(L2) (R4Pc2– = [4,5,4",5",4,5,4,5-tetrakis(1,4,7,10,13-pentaoxotridecamethylene)phthalocyaninate-ion], L is trimethylamine (Me3N), pyridine (py), isoquinoline (iqnl), triethylamine (Et3N), pyrazine (pyz)) was developed. The preparation technique involves selective decarbonylation of (R4Pc)Ru(CO)(MeOH) on treatment with Me3NO in excess N-donor solvent.
A new azophenol type chromogenic ionophore based on the p-tert-butylcalix[4]arenediazacrown ether was prepared: the ionophore exhibited a pronouncedly selective chromogenic behaviour toward Hg2+ ions among the surveyed guests of alkali, alkaline earth, transition and heavy metal ions in liquid-liquid extraction experiments.
Fluorescence and transient absorption measurements show that in strongly coupled ZnPc-C60 and H2Pc-C60 dyads charge-separated states are formed; large -delta GCR degree and small lambda assist in stabilising ZnPc(.+)-C60.-/H2Pc(.+)-C60.-.
Novel zinc phthalocyanine (ZnPc)/fullerene ligand (L) ensembles are assembled following simple biomimetic principles, which upon photoexcitation give rise to intra complex electron transfer quenching of the 1*ZnPc fluorescence.
A novel donor-acceptor bisphthalocyanine (bis-Pc, 1) in which two different Pc units (Zn(II)-Pc and Ni(II)-Pc) are linked via vinylene spacers to the pseudopara positions of a central [2.2]paracyclophane moiety is described. The synthesis of 1 is achieved by two successive Heck reactions of pseudopara-divinyl[2.2]paracyclophane 9 with, sequentially, a zinc(II)- and a nickel(II)-iodophthalocyanine (4 and 5, respectively). The self-assembly ability of 1, which is the result of the complementary donor-acceptor character of its phthalocyanine units, has been assessed by a variety of techniques. It is revealed that 1 forms one-dimensional aggregates of nanometer-sized dimension, whereas equimolar mixtures of the donor and acceptor Pc subunits 2 and 3, although strongly interacting, do not give large arrays. The aggregates of 1 represent a novel type of supramolecular polymers based mainly upon donor-acceptor interactions.
A novel chemical sensor for the colorimetric detection of mercuric salts is described. The sensor is based on a mesoporous nanocrystalline TiO2 film sensitised with a ruthenium dye; immersion of this film in an aqueous solution of Hg2+ results in a rapid colorimetric response, with both a high selectivity and a sub-micromolar sensitivity.
A chromogenic chemosensor for Hg2+ sensing in aqueous environments is reported. The system uses a dithia-dioxa-aza crown binding site and a squaraine backbone as reporter. Additionally, squaraine aggregation phenomena have been explored for searching new sensing concepts in aqueous environments. The probe allows discrimination of Hg2+ over other thiophilic cations and shows a remarkable selective chromogenic double signaling (via the 647 and/or 560 nm bands) of Hg2+ in aqueous environments at nanomolar levels.
Nonlinear optics (NLO) have been drawing interest for a few decades because of their importance in the domains of photoelectronics and photonics. This review covers the important advances obtained to date in the field of the NLO properties phthalocyanines and analogues. Whereas for 1D systems such as polyenes the correlation between structure and NLO response is relatively well developed, much progress is recently being achieved for 2D systems such as Pcs and porphyrins. Such questions as the role of molecular symmetry and multipolar character, metal complexation, peripheral and axial substitution, and core modification are clarified..
Induction of self-organization between zinc phthalocyanine (ZnPc) and C60 moieties in a novel amphiphilic ZnPc-C60 salt results in uniformly nanostructured 1-D nanotubules. Their photoreactivity, in terms of ultrafast charge separation (i.e., approximately 1012 s-1) and ultraslow charge recombination (i.e., approximately 103 s-1), is remarkable. In addition, the observed ZnPc*+-C60*- lifetime of 1.4 ms implies, relative to that of the monomeric ZnPc-C60 ( approximately 3 ns), an impressive stabilization of 6 orders of magnitude.
Sodium borohydride-based hydride generation was automated by using programmable flow within the lab-on-valve module. Mercury vapor, generated in the reaction mixture, was extracted in a gas/liquid separator. The gas-expansion separator was miniaturized and compared with the performance of a novel gas separator that exploits the combination of Venturi effect and reduced pressure. Cold vapor atomic spectroscopy was used as a model system, with detection of mercury by absorption at 254 nm and limit of detection of 9 microg of Hg/L, using 300 microL of sample and 100 microL of borohydride. This work introduces, for the first time, sequential injection technique for hydride generation, highlights advantages of using programmable flow, and outlines means for miniaturization of assays based on spectroscopy of volatile species.
A novel ZnPc-C60 dyad (3), in which two photoactive units are brought together by a phenylenevinylene spacer has been synthesized. The synthetic strategy en route toward 3 involves a Heck reaction to attach 4-vinylbenzaldehyde to a monoiodophthalocyanine precursor, followed by standard cycloaddition of azomethine ylides (generated from the formylPc derivative and N-methylglycine) to one of the double bonds of C60. Electrochemical studies reveal that in 3 the ZnPc is about 39 mV more difficult to oxidize than in the corresponding ZnPc reference, which points to appreciable electronic communication between ZnPc and C60 in the ground state. In the excited state, photoexcitation leads to the formation of a charge-separated ZnPc*+-C60*- state, for which a lifetime of 130 ns was determined in THF. Hetero-association between complementary Pcs (1 and 2 or 3 and 2), which carry different peripheral functionalities (i.e., either electron-donating alkoxy groups or electron-deficient alkylsulfonyl chains) was assessed by different techniques. They provided evidence for donor-acceptor 1:1 complex formation with a stability constant of ca. 10(5) M(-1) in CHCl3. Interestingly, hetero-association of ZnPc-C60 dyad 3 with an electron-deficient PdPc (2) allowed the construction of supramolecular triads, in which a substantial stabilization of the radical pair is seen relative to that of the covalently linked dyad ZnPc-C60 (3).
A new cold vapor technique within the context of green chemistry is described for determination of mercury in liquid samples following high-intensity ultrasonication. Volatile Hg evolved in a sonoreactor without the use of a chemical reducing agent is carried to a quartz cell kept at room temperature for measurement of the atomic absorption. The mechanism involved lies in the reduction of Hg(II) to Hg(0) by reducing gases formed upon sonication and subsequent volatilization of Hg(0) due to the degassing effect caused by the cavitation phenomenon. Addition of a low molecular weight organic acid such as formic acid favors the process, but vapor generation also occurs from Hg solutions in ultrapure water. The detection limit of Hg was 0.1 microg/L, and the repeatability, expressed as relative standard deviation, was 4.4% (peak height). Addition of small amounts of oxidizing substances such as the permanganate or dichromate anions completely suppressed the formation of Hg(0), which confirms the above mechanism. Effect of other factors such as ultrasound irradiation time, ultrasound amplitude, and the presence of concomitants are also investigated. Some complexing anions such as chloride favored the stabilization of Hg(II) in solution, hence causing an interference effect on the ultrasound-assisted reduction/volatilization process.
We have prepared three isomeric donor-acceptor systems, in which two phthalocyanine (Pc) units have been attached to the 1-,5- (1a), 1-,8- (1b), or 2-,6- (1c) positions of a central anthraquinone (AQ) moiety, leading to packed (1b) or extended (1a and 1c) topologies. The electronic interactions between the donor and the acceptor in the ground state or in the excited states have been studied by different electrochemical and photophysical techniques. Due to the markedly different topologies, we have been able to modify these interactions at the intramolecular level and, by a proper choice of the solvent environment, at the intermolecular level within aggregates. In triad 1b, the ZnPc units are forced to pi-stack cofacially and out of the plane of the AQ ring. Consequently, this molecule shows strong inter-Pc interactions that give rise to intramolecular excitonic coupling but a relatively small electronic communication with the AQ acceptor through the vinyl spacers. On the contrary, the 1-,5- or 2-,6-connections of triads 1a and 1c allow for an efficient pi-conjugation between the active units that extends over the entire planar system. These two molecules tend to aggregate in aromatic solvents by pi-pi stacking, giving rise to J-type oligomers. Photoexcitation of the Pc units of 1a-c results in the formation of the Pc.+-AQ.- charge transfer state. We have demonstrated that the kinetics of these electron transfer reactions is greatly dependent on the aggregation status of the triads.
A novel supramolecular electron donor-acceptor hybrid (1) has been designed through axial coordination of a perylenebisimide moiety [BPyPDI], bearing two 4-pyridyl substituents at the imido positions, to the ruthenium(II) metal centers of two phthalocyanines [Ru(CO)Pc]. This modular protocol enables access to electron donor-acceptor hybrids with potentially great design flexibility. The new array (1) has been characterized by standard spectroscopic methods, and its photophysical behavior has been established by using ultrafast and fast time-resolved techniques. Photoexcitation of either chromophore leads to a product that is essentially identical for both pathways, that is, evolving from the [Ru(CO)Pc] or [BPyPDI] singlet excited state. Features of the photoproduct are new transient maxima at 530 and 725 nm, plus transient minima at 580 nm and 650 nm. Based on the radiolytically generated [BPyPDI*-] (i.e., one-electron reduction of [BPyPDI]) and [Ru(CO)Pc*+] (i.e., one-electron oxidation of [Ru(CO)Pc]) features, which in the 300 and 900 nm range remarkably resemble those noted for photoexcited 1, we attribute the photolytically generated species to the composite spectrum of the [Ru(CO)Pc*+ -BPyPDI*- -RuCOPc] radical ion pair state. Its lifetime, which is on the order of 115 +/- 5 ns, reveals a significant stabilization and confirms that the strongly exothermic charge recombination dynamics are placed deeply in the inverted region of the Marcus parabola.
The optical and electrochemical properties of the ruthenium phthalocyanine complexes [[(t-Bu)4Pc]Ru(4-Rpy)2], where R = NO2, Me, NH2, and NMe2, are reported. The electron density at the macrocycle may be adjusted using the axial ligand substituents, which have varying electron-donating/withdrawing strengths. Electrochemical data show that the axial pyridine ligand substituents exert significant influence over the phthalocyanine ring-based redox processes. The axial ligands also influence the electronic absorption properties of the complexes with influence also being observed in the electrogenerated oxidized and reduced species.
- de la Torre
- Mortimer
Absorption and Magnetic Circular Dichroism Spectral Properties of Phthalocyanines
- M J Stillman
- Stillman