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Biological investigation of I-131-labeled new water soluble Ru(II) polypyridyl complex
Abstract
New [Ru(L1)(dcbpy)(NCS)2] complex was synthesized in a one-pot reaction starting from [RuCl2(p-cymene)]2, where the ligands (dcbpy=4,4'-dicarboxy-2,2'-bipyridine, L1=dipyrido[3,2-a:2',3'-c]phenazine-11-ylcarbonyl)-sodium) are introduced sequentially. The resulting complex was characterized by IR, NMR, and elemental analysis. The complex was labeled with I-131. Biodistribution study of the complex was carried out using 131I-labeled [Ru(L1)(dcbpy)(NCS)2] complex. The biodistribution study performed with albino Wistar male rats has shown that the complex has high uptake in the lung, small intestine, fat, and spleen.
... These functional groups bring cationic properties to the material. L1 is chosen not only to increase molar extinction coefficient of the complex, but also to enable the material soluble in water [16]. The compound can also show pH sensitive properties because of the -COOH groups. ...
... The compound can also show pH sensitive properties because of the -COOH groups. As a result, it is also soluble in both acidic and basic media [16,17]. L2 is one of the most widely used ligands for ruthenium complexes that employed in Dye Sensitized Solar Cells [7][8][9][17][18][19][20]. ...
... The molar extinction coefficient for this is 13,800 M −1 cm −1 . These results are very close to the reported MLCT absorptivities of other similar complexes [1,16,20]. The bands at 221 nm and 278 nm and the shoulder observed at around 314 nm can be assigned to the intraligand π-π* transition of the ligands L1 and L2. ...
The stability of the optical parameters of a ruthenium polypyridyl complex (Ru-PC K314) film under varying annealing temperatures between 278 K and 673 K was investigated. The ruthenium polypyridyl complex thin film was prepared on a quartz substrate by drop casting technique. The transmission of the film was recorded by using Ultraviolet/Visible/Near Infrared spectrophotometer and the optical band gap energy of the as-deposited film was determined around 2.20 eV. The optical parameters such as refractive index, extinction coefficient, and dielectric constant of the film were determined and the annealing effect on these parameters was investigated. The results show that Ru PC K314 film is quite stable up to 595 K, and the rate of the optical band gap energy change was found to be 5.23x10− 5 eV/K. Furthermore, the thermal analysis studies were carried out in the range 298–673 K. The Differential Thermal Analysis/Thermal Gravimmetry/Differantial Thermal Gravimmetry curves show that the decomposition is incomplete in the temperature range 298–673 K. Ru-PC K314 is thermally stable up to 387 K. The decomposition starts at 387 K with elimination of functional groups such as CO2, CO molecules and SO3H group was eliminated between 614 K and 666 K.
... Ruthenium metal complexes with polypyridyl ligands receive considerable interest due to their excellent photochemical stability, strong visible absorption, efficient luminescence, and relatively long life metal to ligand charge transition (MLCT) [1][2][3][4][5][6][7][8][9]. This class of complexes has attracted great interest, not only from science but also from industry side because of the great photovoltaic performance in photovoltaic applications in terms of both conversion yield and long-term stability. ...
... It is known in the literature [2] that, such great photovoltaic performance was achieved by using polypyridyl complexes of ruthenium and osmium. Several ruthenium complexes containing anchoring groups such as carboxylic acid, dihydroxy, and phosphonic acid on pyridine ligands have been used as dyes for photovoltaic applications [1][2][3][4][5][6][7][8][9]. In these complexes, the anchoring groups are responsible for immobilizing the dye on the nanocrystalline TiO 2 surface. ...
Thermal behavior of [cis-(dithiocyanato)(1,10-phenanthroline-5,6-dione)(4,4′-dicarboxy-2,2′-bipyridyl)ruthenium(II)], cis-[Ru(L1)(L2)(NCS)2] (where the ligands were L1 = 1,10-Phenanthroline-5,6-dione, L2 = 4,4′-dicarboxy-2,2′-bipyridyl) was investigated by DTA/TG/DTG
measurements under inert atmosphere in the temperature range of 298–1473 K as well as by XRD analysis of the final product.
After making detailed analysis and comparison of thermogravimetrical and MS measurements of ruthenium complex, the decomposition
mechanism of that complex was suggested. The values of activation energy and reaction order of the thermal decompositions
were calculated by Ozawa Non-isothermal Method for all decomposition stages. The calculated activation energies vary in between
32 and 49 kJ mol−1.
... Ruthenium-(II) bipyridine-type complexes with polypyridyl ligands are very useful building blocks for the construction of supramolecular species capable of exhibiting peculiar photochemical stability, strong visible absorption, efficient luminescence, and a relatively long lived metal to ligand charge transition (MLCT) [1][2][3][4][5][6][7][8][9][10]. Ruthenium-(II) bipyridine complexes have been the focus of considerable attention for the past half century because of the best photovoltaic performance in photovoltaic applications in terms of both conversion yield and long-term stability. ...
... Recently, these studies have received further interest because of their potential application of polypyridyl compounds in the development of sustainable and environmentally friendly energy [11][12][13]. Several ruthenium complexes have been used as dyes for photovoltaic applications [1][2][3][4][5][6][7][8]. In these complexes, the anchoring groups such as carboxylic acid, dihydroxy, and phosphonic acid on pyridine ligands serve to immobilize the dye on the nanocrystalline TiO 2 surface. ...
Thermal properties of [cis-(dithiocyanato)(4,5-diazafluoren-9-one)(4,4′-dicarboxy-2,2′-bipyridyl)ruthenium(II)], [Ru(L
1)(L
2)(NCS)2] (where the ligands L
1 = 4,5-diazafluoren-9-one, L
2 = 4,4′-dicarboxy-2,2′-bipyridyl) have been investigated by DTA/TG/DTG measurements under inert atmosphere in the temperature range of 30–1155 °C. The mass spectroscopy technique has been used to identify the products during pyrolytic decomposition. The pyrolytic final products have been analyzed by X-ray powder diffraction technique. A decomposition mechanism has been also suggested for the cis-[Ru(L
1)(L
2)(NCS)2] complex based on the results of thermogravimetrical and mass analysis. The values of the activation energy, E* have been obtained by using model-free Kissenger–Akahira–Sunose and Flyn–Wall–Ozawa non-isothermal methods for all decomposition stages. Thirteen kinetic model equations have been tested for selecting the best reaction models. The best model equations have been determined as A2, A3, D1, and D2 which correspond to nucleation and growth mechanism for A2 and A3 and diffusion mechanism for D1 and D2. The optimized average values of E* are 31.35, 58.48, 120.85, and 120.56 kJ mol−1 calculated by using the best model equations for four decomposition stages, respectively. Also, the average Arrhenius factor, A, has been obtained as 2.21, 2.61, 2.52, and 2.21 kJ mol−1 using the best model equation for four decomposition stages, respectively. The ΔH*, ΔS*, and ΔG* functions have been calculated using the optimized values.
... Radioiodine complexes are used in pharmacokinetic studies. [6][7] In the present study, the authors aimed to synthesize a new imidazolium salt and to evaluate its pharmacokinetic by in vivo and antitumor potentials by in vitro studies. ...
Imidazolium salts have antitumor potential and toxicological effects on various microorganisms. The authors' aim is to synthesize a new imidazolium salt and to assess its pharmacokinetic and antitumor potentials by in vitro and in vivo studies. In this study, bis(trifluoromethanesulfonyl) imide (ITFSI) was synthesized and labeled with 131I using the iodogen method. The efficiency of radiolabeling was determined with high yield (95.5%±3.7%). Pharmacokinetic properties of the compound were investigated in albino Wistar rats using radiolabeled compound. The radiolabeled compound (131I-ITFSI) has been stable during a period of 3 hours in human serum. The uptake of 131I-ITFSI reached maximum in the spleen, liver, and blood at 60 minutes, large intestine and heart at 30 minutes, and ovary at 120 minutes. It is observed that intracellular uptake of the radiolabeled compound is higher in the CaCo-2 (colon adenocarcinoma tumor) cell line than HEK-293 (human epithelial kidney) cell line. In further study, antitumor potential of ITFSI on a colon adenocarcinoma tumor-bearing animal model may be investigated.
... The amount of iodogen studies showed that oxidized iodine can be easily bind to the benzene ring via an electrophilic substitution reaction [19,[28][29][30][31]. ...
In this study, the biological potential of a nickel
chlorophyll derivative (Ni-PH-A) as a multimodal agent
for tumor imaging and photodynamic therapy (PDT) was
investigated. Optimum conditions of labeling with 131I
were investigated and determined as pH 10 and 1 mg
amount of iodogen. Biodistribution results of 131I labeled
Ni-PH-A in female rats indicated that radiolabeled Ni-PHA
maximum uptake in the liver, spleen and ovary was
observed at 30 min. Intercellular uptake and PDT efficacy
of Ni-PH-A were better in MDAH-2774 (human ovarian
endometrioid adenocarcinoma) than in MCF-7 (human
breast adenocarcinoma) cells. Ni-PH-A might be a
promising multimodal agent for lung, ovary and liver tumor
imaging and PDT.
... A stock sample solution was prepared as 2 mg glycosides extract in 1 mL distilled water. The sample was labeled with 131 I using the iodogen method under the same conditions as previously described by Yurt Lambrecht et al. [8,10,11]. During the radiolabeling procedure, the pH of the sample solution (0.1 mg/mL) was adjusted to 3 using 0. ...
Crude extract of S. officinalis L. was found to have suspending agent, hemolytic, antitumor, antioxidant and antimicrobial
activities. Its major components benzofurans and benzofuran glycosides have antifungal, anticancer, antibacterial and anticomplement
activities and display acetylcholinesterase-cyclooxygenase inhibitory and cytotoxic properties. Recently, it has been reported that
egonolgentiobioside is a valuable target for structural modification and warrants further investigation for its potential as a novel
pharmaceutical tool for the prevention of estrogen deficiency induced diseases.
... The principal reason is their remarkable chemical stability and photophysical properties. These complexes have a wide range of applications in many research fields such as light harvesting systems and photochemically driven molecular devices, as well as photocatalysts and as biological surveys [8][9][10][11][12][13][14][15]. Moreover, ruthenium dyes are also promising candidates for a variety of sensors and switches [16][17][18] due to their semiconducting properties. ...
We report the characterization of novel ruthenium polypyridyl complex (Ru-PC) based sensor film with a thickness of 50nm coated on a quartz substrate using a spin coating method for humidity detection. The resulting complex [Ru(L1)2(L2)] was synthesized in a one-pot reaction starting from [RuCl2(p-cymene)]2, where the ligands (L1=4,7-diphenyl-1,10-phenanthroline-disulfonic acid disodium salt and L2=4,4′-dicarboxy-2,2′-bipyridine) were characterized by NMR, mass spectrometry (MALDI), elemental analysis and UV–vis spectroscopy. The humidity adsorption and desorption kinetics of the ruthenium complex were investigated using the Quartz Crystal Microbalance (QCM) technique. The Langmuir model was used to determine adsorption and desorption rates and Gibbs free energy over the 11–97% relative humidity range. Our experimental results show that Ru-PC films have a great potential for humidity sensing applications at standard conditions (i.e. room temperature).
This study aims to investigate radiolabeled Cefpodoxime Proxetil loaded chitosan (CP–CS) nanoparticles as nuclear imaging infection agent to Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). The encapsulation efficiency of Cefpodoxime Proxetil was found 82 ± 2%. CP and CP–CS nanoparticles were radiolabeled with Tc-99 m. The radiochemical purity of 99mTc–CP and 99mTc–CP–CS nanoparticles were determined by RTLC as 89 ± 3% and 94 ± 2% respectively. In vitro bindings of 99mTc–CP–CS nanoparticles to S. aureus and E. coli were found higher than 99mTc–CP bindings.
The discovery of the involvement of nitric oxide (NO) in several physiological and pathophysiological processes launched a spectacular increase in studies in areas such as chemistry, biochemistry, and pharmacology. As a consequence, the development of NO donors or scavengers for regulation of its concentration and bioavailability in vivo is required. In this sense, ruthenium nitrosyl ammines and aliphatic tetraazamacrocyles have attracted a lot of attention due to their unique chemical properties. These complexes are water soluble and stable in solution, not to mention that they can deliver NO when photochemically or chemically activated by the reduction of the coordinated nitrosonium (NO+). The tuning of the energies of the charge transfer bands, the redox potential, and the specific rate constants of NO liberation, in both solution and matrices, is desirable for the achievement of selective NO delivery to biological targets, hence making the ruthenium ammines and aliphatic tetraazamacrocyles a quite versatile platform for biological application purposes. These ruthenium nitrosyls have shown to be active in firing neurons in mouse hippocampus, performing redox reactions in mitochondria, acting in blood pressure control, exhibiting cytotoxic activities against trypanosomatids (T.cruzi and L.major) and tumor cells. This tailoring approach is explored here, being heavily supported by the accumulated knowledge on the chemistry and photochemistry of ruthenium complexes, which allows NO donors/scavengers systems to be custom made designed.
A new, low cost solar cell - based on work done by Professor Grätzel - was evaluated for power generation applications. The main effort at ABB was directed towards the development of cells with high efficiencies and towards the development of production methods for the electrodes. Using optimized electrodes made by screen-printing techniques, an efficiency of 9.4% could be obtained for small electrodes (0.5 cm2). Lifetimes of more than 10 months without degradation could be achieved at the EPF Lausanne using this type of cell.
We report a photoelectrochemical solar cell (PEC) with in situ storage, operating at 11.3% overall solar to electrical conversion efficiency, with a generated power insensitive to daily fluctuations in solar radiation. A primary advantage of PECs, compared to photovoltaic solar cells, had been their proposed capacity for in situ storage by the addition of a single electrochemical half cell1. Several systems combining photoelectrochemical conversion with electrochemical storage have been presented with maximum efficiencies of approximately 3 per cent. A series of polysulphide solution effects2–5 resulted in a high efficiency caesium polysulphide n-Cd(Se,Te) single crystal PEC6. As will be shown, this leads to an autonomous cell with sufficient voltage to bypass the previous necessity for bipolar dual photoelectrode storage, allowing single photoelectrode induced electrochemical storage, with a high continuous output.
We have quantitatively investigated the charging of colloidal ZnO films by cyclic voltammetry and potential step measurements. Up to six electrons can be stored on each colloidal particle of the film (mean particle diameter 5.9 nm) before zinc reduction occurs. Fluorescence and absorbance of the films are already strongly influenced in potential regions where less than one electron is stored on each particle. Potentiostatically controlled and time-resolved photocurrent measurements show the influence of trap filling as well as the role of the electrolyte on the charge transport through the films.
A series of CN-bridged trinuclear Ru complexes of the general structure [RuL2(μ-(CN)Ru(CN)L2′)2] where L is 2,2′-bipyridine-4,4′-dicarboxylic acid and L′ is 2,2′-bipyridine (1)2,2′-bipyridine-4,4′-dicarboxylic acid (2), 4,4′-dimethyl-2,2′-bipyridine (3), 4,4′-diphenyl-2,2′-bipyridine (4), 1,10-phenanthroline (5), and bathophenanthrolinedisulfonic acid (6) have been synthesized, and their spectral and electrochemical properties investigated. The two carboxylic functions on the 2,2′-bipyridine ligand L serve as interlocking groups through which the dye is attached at the surface of TiO2 films having a specific surface texture. The role of these interlocking groups is to provide strong electronic coupling between the π* orbital of the 2,2′-bipyridine and the 3d-wave-function manifold of the conduction band of the TiO2, allowing the charge injection to proceed at quantum yields close to 100 %. The charge injection and recombination dynamics have been studied with colloidal TiO2, using laser photolysis technique in conjunction with time-resolved optical spectroscopy. Photocurrent action spectra obtained from photo-electrochemical experiments with these trinuclear complexes cover a very broad range in the visible, making them attractive candidates for solar light harvesting. Monochromatic incident photon-to-current conversion efficiencies are strikingly high exceeding 80% in some cases. Performance characteristics of regenerative cells operating with these trinuclear complexes and ethanolic triiodide/iodide redox electrolyte have been investigated. Optimal results were obtained with complex 1 which gave a fill factor of 75 % and a power conversion efficiency of 11.3% at 520 nm.
Recently, a paper was published by the Lausanne Group headed by Dr. M. Graetzel which reported a simple low cost 7% efficient photo electrochemical solar cell made from a trinuclear Ru dye complex adsorbed on the very rough surface of a colloidal TiO2 film. In the current paper, a verification of this result is presented using procedures described in the literature. Measurements are reported in stimulated and natural sunlight which confirm that the efficiency is indeed in the range previously reported. Predicted Air Mass 1.5 photo currents are compared to those obtained from fabricated dye sensitized cells. Although current densities of 12 mA/cm2 and voltages of over 0.6 V are measured,it is found that corresponding fill factors, less than 0.6, limit the performance of the cell under solar illumination. The basic economics of such a device are outlined and it is proposed that cell costs of $ 0.6 per peak watt could be possible if the longevity of the cell is at least 15 years.
Im Rahmen von Untersuchungen der Photoanregung bestimmter Halbleiter wegen ihrer Bedeutung für die Umwandlung von Solarenergie wurde die Anregung von kolloidalen Anatas-Partikeln und polykristallinen Elektroden durch Tris-[2,2′-bipyridyl-4,4′-dicarboxylat]- ruthenium(II)-dichlorid spektroskopisch untersucht.
The preparation, surface attachment, optical, and photoelectrochemical properties of metal cyanide complexes, cis-[(4,4[prime]-(CO[sub 2]H)[sub 2]bpy)[sub 2]M(CN)[sub 2]] where M = Ru(II) and Os(II), attached to sol-gel processed TiO[sub 2] electrodes are reported. The specific sol-gel process provides a route to stable, high surface area anatase TiO[sub 2] films. With surface anchored [(4,4[prime]-(CO[sub 2]H)[sub 2]bpy)[sub 2]Ru(CN)[sub 2]]RB we report incident-photon-to-current efficiencies exceeding 90%. The net photocurrent scales linearly over 5 decades of incident irradiance. The molecular level similarity of the two polypyridyl complexes allows for a meaningful comparison of the electrooptical properties of Ru(II) and Os(II) derivatized surfaces. A kinetic interpretation with different sacrificial electron donors provides insight into the rate limiting step(s) in the photosensitization process. An increased rate of electron tunneling from the semiconductor conduction band to the oxidized dye and a more sluggish halide oxidation rate are believed to be responsible for a low photocurrent efficiency observed with surface-anchored [(4,4[prime]-(CO[sub 2]H)[sub 2]-bpy)[sub 2]Os(CN)[sub 2]]. The results and interpretation suggest methods for developing more efficient photovoltaic devices. 35 refs., 8 figs., 2 tabs.
Ruthenium(II) and osmium(II) complexes of 2,2′-bipyridyls (bipy) and 1,10-phenanthrolines (phen) are identified as feasible dyes for use in luminescent solar collectors. Twenty-seven RuII(bipy)32+ complexes are prepared and the absorption and emission spectra of their solutions in EtOH–MeOH at room temperature are reported. Quantum efficiencies, Which are sensitive to oxygen quenching, vary between 0.002 and 0.306 depending upon substituents. The effect of the medium on the spectral properties of selected compounds has also been investigated. Measured quantum yields of non-aqueous solutions are higher than those for aqueous solutions but lower than for doped plastic films.
Visible light irradiation of [Ru(TAP)3]2+(TAP = 1,4,5,8 -tetraazaphenanthrene) in aqueous solutions containing 5′-guanosine-monophosphate (GMP) and subsequent treatment with 1 mol dm–3 HCl yields Ru(TAP)2(2-TAP-G)2+, in which the guanine moiety is bound via N-2 to C-2 of one of the TAP ligands.
Since the synthesis of [Ru(bpy)[sub 3]][sup 2+ ] and its subsequent study in excited-state electron-transfer reactions, much attention has focused on the inclusion of multiple ruthenium chromophores into single molecules. Systems of this type are of interest due to their potential for photoinitiated electron collection. This report illustrates the application of a system with two ruthenium polypyridine chromophores to this problem. This represents the first report of photoinitiated electron collection wherein two covalently coupled ruthenium chromophores function within the same molecule to bring about electron collection. The system described herein is of the form [[(bpy)[sub 2]Ru(dpb)][sub 2]IrCl[sub 2]][sup 5+] (bpy = 2,2[prime]-bipyridine and dpb = 2,3-bis(2-pyridyl)benzoquinoxaline) and is one in a series of mixed-metal trimetallics designed and developed in our laboratory. Photolysis of this complex in the presence of an electron donor dimethylaniline, leads to the production of the doubly reduced species, [[(bpy)[sub 2]Ru(dpb[sup [minus]])][sub 2]IrCl[sub 2]][sup 3+]. Following photolysis, the complex now contains two reduced dpb bridging ligands coordinated to a central iridium core. 13 refs., 4 figs.
The concept of the “spatially isolated orbital” was introduced to rationalize the unusual optical and magnetic properties determined for metal chelate complexes, ML3n+, in which a chelate ligand, L, as 2,2′-bipyridine possesses low energy π* orbitals. Optical excitation or electrochemical reduction produces a species whose effective symmetry is that of the ligand alone. This review discusses the results associated with the redox orbital emphasizing anomalies that occur.
A “supramolecular approach” to the design of photosensitizers for wide band-gap semiconductors is sketched. Interesting possibilities are identified in terms of photoinduced charge separation and antenna effect. A number of experimental studies are discussed to emphasize: (i) the versatility of systems based on transition metal complexes, in terms of tunability and synthetic control of photophysical and redox properties; (ii) the availability of a variety of specific fast photophysical methods (luminescence techniques, UV/VIS laser flash spectroscopy, time-resolved resonance Raman and infrared spectroscopies) for monitoring intercomponent energy and electron transfer processes; (iii) the achievement of a fair degree of kinetic control on such processes by molecular design.
The complexes cis-Pt(O2CNEt2)2(PR3)2 (R = Ph, Et) and Pt(O2CNEt2)2(DPPE) [DPPE = 1,2-bis(diphenylphosphino)ethane] were prepared by the reaction of the corresponding phosphino-chloro complexes of platinum with Ag(O2CNEt2). The new N,N-diethylcarbamato complexes are excellent precursors for the high-yielding preparation of the corresponding carbonato derivatives Pt(CO3)(PR3)2 or Pt(CO3)(DPPE) by reaction with a stoichiometric amount of water. The carbamato complex cis-Pt(O2CNEt2)2(PPh3)2 reacts with CO producing the carbamoyl derivative cis-Pt[C(O)NEt2]2(PPh3)2. The chloro-carbamoyl complex, prepared by reacting cis-PtCl2(PPh3)2 with NHEt2 and CO, and recrystallized from toluene as the solvated species trans-PtCl[C(O)NEt2](PPh3)2·2 C6H5Me has been structurally characterized.
Whether the DNA base pair stack might serve as a medium for efficient, long-range charge transfer has been debated almost since the first proposal of the double-helical structure of DNA. The consequences of long-range radical migration through DNA are important with respect to understanding carcinogenesis and mutagenesis. Double-helical DNA has in its core a stacked array of aromatic heterocyclic base pairs, and this molecular π stack represents a unique system in which to explore the chemistry of electron transfer. We designed a family of metal complexes which bind to DNA by intercalative stacking within the helix; these metallointercalators may be usefully applied in probing DNA-mediated electron transfer. Here we describe a range of electron transfer reactions we carried out which are mediated by the DNA base paired stack. In some cases, DNA serves as a bridge, and spectroscopic analyses permit us to probe how the π stack couples DNA-bound donors and acceptors. These studies point to the sensitivity of coupling to DNA intercalation. However, if the DNA π stack effectively bridges donors and acceptors, the base-pair stack itself might serve not only as a conduit for electron transfer in DNA, but also in reactions initiated from a remote position. We carried out a series of reactions involving oxidative damage to DNA arising from the remotely positioned oxidant on the helix. The implications of long-range charge migration through DNA to effect damage are substantial. As in other DNA-mediated charge transfers, these reactions are highly dependent on DNA intercalation and the integrity of the intervening base-pair stack, but not on molecular distance. Furthermore, a physiologically important DNA lesion, the thymine dimers, can be reversed in a reaction initiated by electron transfer. This repair reaction can also be promoted from a distance as a result of long-range charge migration through the DNA base pair stack.
The electron-hole pair formation that occurs at the interface between a semiconductor and a solution upon absorption of light
leads to oxidation or reduction reactions of solution species. The principles of such photodriven processes are described
as well as applications of semiconductors in electrochemical cells and as particulate systems for carrying out heterogeneous
photocatalysis and photoelectrosynthesis.
THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.
The preparation, characterization and photoconversion properties of [Ru(II)(dcbpy)(terpy)X]X·3H2O where X=Cl, SCN, CN were carried out. For the fabrication of a solar cell, TiO2 and platinum coated conducting glasses were used. The performance of the complexes for the conversion of solar radiation into electricity was found to be good, with maximum output voltage (Voc) and short circuit current (Isc).
The lifetime τn and diffusion coefficient Dn of photoinjected electrons have been measured in a dye-sensitized nanocrystalline TiO2 solar cell over 5 orders of magnitude of illumination intensity using intensity-modulated photovoltage and photocurrent spectroscopies. τn was found to be inversely proportional to the square root of the steady-state light intensity, I0, whereas Dn varied with I00.68. The intensity dependence of τn is interpreted as evidence that the back reaction of electrons with I3- may be second order in electron density. The intensity dependence of Dn is attributed to an exponential trap density distribution of the form Nt(E) exp[−β(E − Ec)/(kBT)] with β ≈ 0.6. Since τn and Dn vary with intensity in opposite senses, the calculated electron diffusion length Ln = (Dnτn)1/2 falls by less than a factor of 5 when the intensity is reduced by 5 orders of magnitude. The incident photon to current efficiency (IPCE) is predicted to decrease by less than 10% over the same range of illumination intensity, and the experimental results confirm this prediction.
Intensity modulated photovoltage spectroscopy (IMVS) and intensity modulated photocurrent spectroscopy (IMPS) are used to evaluate the charge-collection efficiency of dye-sensitized nanocrystalline TiO2 solar cells. The charge-collection efficiency of the photoinjected electrons from dye sensitization is estimated from the respective time constants for charge recombination at open circuit τoc and the combined processes of charge collection and charge recombination at short circuit τsc obtained by IMVS and IMPS measurements. Three models are developed for relating the charge-collection efficiency to τoc/τsc. The first model determines the charge-collection efficiency from τoc/τsc without considering the underlying physical processes measured by IMVS and IMPS. The second model obtains τoc/τsc by simulating the frequency response of IMVS and IMPS from the time-dependent continuity equation for simplified conditions. The third model determines the time constants for IMVS and IMPS from electron-concentration profiles calculated for constant light intensity and more realistic conditions. To obtain a realistic steady-state electron concentration profile, a nonlinear dependence of the rate of recombination on the electron concentration in the TiO2 film is considered. Furthermore, the continuity equation is modified to account for charge trapping and detrapping. For the first time, expressions are derived for calculating the time constants from the steady-state electron concentration profile. The validity of this method is demonstrated for the second model from which the exact IMPS and IMVS responses are calculated. The three models are compared with each other. A simple expression is derived for calculating the charge-collection efficiency from the measured values of τoc/τsc and the light intensity dependence of τoc.
The use of antenna-sensitizer molecular devices is proposed as a possible strategy to increase the light harvesting efficiency of sensitized semiconductors. To illustrate this approach, the cyano-bridged trinuclear complex [Ru(bpy)2-(CN)2]2Ru(bpy(COO)2) 22- has been synthesized and studied. The complex adsorbs on TiO2 via the negativity charged -Ru(bpy(COO)2)2- central unit. The photophysical behavior in solution and the photoelectrochemical behavior on TiO2 have been studied. Emission and excitation spectra show that in this complex the light energy absorbed by the terminal Ru(bpy)2(CN)2 (antenna) groups is efficiently funneled to the central -Ru(bpy(COO)2)2- (sensitizer) fragment. Photochemical spectra on TiO2 demonstrate that the light absorbed by the antenna fragments is efficiently used for sensitization of the semiconductor.
Since the synthesis of [Ru(bpy)(3)](2+) and its subsequent study in excited-state electron-transfer reactions, much attention has focused on the inclusion of multiple ruthenium chromophores into single molecules. Systems of this type are of interest due to their potential for photoinitiated electron collection. This report illustrates the application of a system with two ruthenium polypyridine chromophores to this problem. This represents the first report of photoinitiated electron collection wherein two covalently coupled ruthenium chromophores function within the same molecule to bring about electron collection. The system described herein is of the form {[(bpy)(2)Ru(dpb)]2IrCl2}(5+) (bpy = 2,2'-bipyridine and dpb = 2,3-bis(2-pyridyl)benzoquinoxaline) and is one in a series of mixed-metal trimetallics designed and developed in our laboratory. Photolysis of this complex in the presence of an electron donor, dimethylaniline, leads to the production of the doubly reduced species, {[(bpy)(2)Ru(dpb(-))]2IrCl2}(3+). Following photolysis, the complex now contains two reduced dpb bridging ligands coordinated to a central iridium core. In a previous study we have shown that the central core, [Ir(dpb)(2)Cl-2](+), is able to deliver electrons ''stored'' on the bridging ligands to a substrate. The details of the photoinitiated electron collection process are described herein.
A series of ruthenium(II) complexes have been prepared which contain two phenanthroline ligands and a third bidentate ligand which is one of a set of derivatives of the parent dipyrido[3,2-a:2',3'c]phenazine (DPPZ) ligand. The spectroscopic properties of these complexes in the presence and absence of DNA have also been characterized. The derivatives have been prepared by condensation of different diaminobenzenes or diaminopyridines with the synthetic intermediate bis(1,10-phenanthroline)(1,10-phenanthroline-5,6-dione)ruthenium(II). [Ru(phen)2DppZ]2+, like [Ru(bpy)2DPPZ]2+, acts as a molecular "light switch" for the presence of DNA, displaying no detectable photoluminescence in aqueous solution but luminescing brightly on binding to DNA. None of the DPPZ derivatives prepared show comparable "light switch" enhancements, since some luminescence may be detected in aqueous solution in the absence of DNA. For some complexes, however, luminescence enhancements of a factor of 20-300 are observed on binding to DNA. For these and the parent DPPZ complexes, the large enhancements observed are attributed to a sensitivity of the ruthenium-DPPZ luminescent charge-transfer excited state to quenching by water; although these complexes show little or no luminescence in water, appreciable luminescence is found in acetonitrile. Other derivatives show little solvent sensitivity in luminescence, and these, like Ru(phen)32+, display moderate enhancements (20-70%) on binding to DNA. [Ru(phen)2DppZ]2+ and its derivatives all show at least biexponential decays in emission. Two binding modes have been proposed to account for these emission characteristics: a perpendicular mode where the DPPZ ligand intercalates from the major groove such that the metal-phenazine axis lies along the DNA dyad axis, and another, side-on mode where the metal-phenazine axis lies along the long axis of the base pairs.
Ruthenium polypyridyl compounds, cis-[4,4'-(CO2H)(2)-2,2'-bipyridine]Ru-2(X)(2) and cis-[5,5'-(CO2H)(2)-2,2'-bipyridine]Ru-2(X)(2) where X = Cl-, CN-, and SCN-, have been prepared, spectroscopically characterized, and anchored to high surface area TiO2 electrodes for the conversion of visible light into electricity. Vibrational studies reveal a surface ester linkage and indicate that the sensitizers bind to TiO2 through a distribution of interfacial interactions in a similar manner. When operating in a photoelectrochemical cell, these materials convert visible photons into electrons. Transition metal sensitizers based on the 5,5'-(CO2H)(2)-2,2'-bipyridine ligand generally enhance photon-to-current efficiencies at low photon energies. Consistent with a previous report, photoanodes based on cis-[4,4'-(CO2H)(2)-2,2'-bipyridine]Ru-2(NCS)(2) are the most efficient under simulated sunlight (Gratzel, M., et al. J. Am. Chem. Soc. 1993, 115, 6382). The observation of an electric field dependent luminescence indicates that radiative recombination of the dye competes with photocurrent production in some cases. A lower limit for the rate of interfacial electron injection is estimated to be k(et) similar to 5 x 10(7) s(-1). A lower photocurrent efficiency observed for sensitizers based on 5,5'-(CO2H)(2)-2,2'-bipyridine stems in part from less efficient electron transfer to the TiO2 surface.
13C Chemical shifts are reported for the ruthenium(II) tris complexes of thirteen 2,2′-bipyridyls and three 1,10-phenanthrolines and for the osmium(II) tris complexes of five 2,2′-bipyridyls. Chelation induced shifts (δcomplex – δligand) are discussed in terms of models for π back-bonding. 13C NMR is shown to be a convenient tool for the direct observation of the geometrical isomerism of complexes formed from monosubstituted ligands.
The chemical and photochemical behaviour of MoS2-van der Waals surfaces in contact with an aqueous electrolyte has been investigated by means of electrochemical techniques. The covalent bonding character of this layer crystal and a molybdenum dz2-band which is split off from the 4d molybdenum conduction band and overlaps the sulfur 3p valence band give rise to reaction behaviour which is very different from that found with polar metal-sulfide compounds: sulfate and not molecular sulfur is the main product of the electrochemical and photochemical oxidation of MoS2 which occurs as p−, n−, or intrinsic semiconductor material. A parallel photochemical liberation of molecular oxygen could be traced on freshly prepared surfaces by means of polarographic techniques. The quantum efficiency for the photoelectrochemical reaction with water in the visible spectral range approaches 100% if a positive electrode potential of 2 V is applied. Several electron-transfer reactions were examined and the interrelation between d-band structure of the layer sulfide and some of its electrochemical behaviour is discussed.
Electron injection from optically excited dye molecules into the depletion layer of polycrystalline n‐TiO 2 electrodes is measured as photocurrent. The characteristic shape of the photocurrent transients has a point of inflection and is controlled by the complete filling of deep traps. The rate equations for the Shockley–Read trapping process are solved numerically for the case of high injection levels, and the shape of the transients is simulated.
New [Ru(L1)(H2dcbpy)(NCS)2] [K30] and [Ru(L2)(H2dcbpy)(NCS)2] [K27] complexes were synthesized in a one-pot reaction starting from [RuCl2(p-cymene)]2, where the ligands (H2dcbpy = 4,4′-dicarboxy-2,2′-bipyridine, L1 = 4,5-diazafluoren-9-one, and L2 = 1,10-phenanthroline-5,6-dione) are introduced sequentially. The resulting complexes were characterized by UV–vis, emission, IR, TGA, NMR, elemental analysis and cyclic voltammetry. The absorption and emission maxima of the two complexes are very similar to one another. The low-energy MLCT absorption maxima of the complexes appear at 524 nm, and the luminescence consists of a single band with a maximum at 700 and 720 nm, respectively, in DMF solution at 298 K. The electrochemical behaviors of the complexes have been studied in CH3CN by cyclic voltammetry. The LUMO energy levels of K27 and K30 were determined as −4.01 and −3.86 eV, respectively. The thermogravimetric analyses (TGA) of the prepared complexes show that the dyes are stable up to about 220 °C. Photodecompositions of the complexes in solution were studied in both ethanol and DMF solvents with a steady-state spectrofluorimeter in time-based mode. The photostability of the compounds in DMF was found to increase twice in comparison to ethanol. Fluorescence quenching experiments of the one simple derivative of PDIs (N,N′-bis(1-ethylpropyl)perylene-3,4,9,10-tetracarboxylic acid (EP-PDI)) in DMF were studied vs. increasing K27 and K30 concentrations to monitor donor/acceptor capability. The rate constants (kq) of EP-PDI for each complex, K27 and K30, were determined as 7.72 × 1012 and 6.52 × 1012 M−1 s−1, respectively. In addition, the free energies of exothermic photo-electron transfer (ET) processes between EP-PDI and complexes K27 and K30 were calculated to be −62.3 and −57.9 kcal mol−1, respectively.
Dye-sensitized colloidal TiO2 film electrodes using a Ru 2,2'-bipyridyl-4,4'-dicarboxylic acid complex were used as photoanodes in photoelectrochem. solar cells. The cells were prepd. following the description by M.K. Nazeeruddin, et al, (1993). An overall light-to-elec. energy conversion efficiency of 7% in 1000 W/m2 light from the ELH lamp was obtained. Practical problems in the prepn. procedure of the solar cell module has so far made long time stability tests impossible. Future developments of the cell are discussed.
The basic principles of conversion of solar energy by photoelectrochemical methods are reviewed. A distinction is made between systems used for conversion into electrical energy and those which are applicable for the production of chemical fuel. Besides photogalvanic cells, the main emphasis is put on semiconductor/electrolyte/metal-devices. The various mechanisms involved in these cells, the conversion efficiencies and the stability of the components are discussed in terms of energy schemes. The properties of these systems are compared with those of pure solid state devices. As far as the photolytic decomposition of water for the production of chemical fuel is concerned, the photoelectrochemical reactions in heterogeneous systems are briefly compared with purely photochemical processes in homogeneous solutions. Various conclusions are made concerning the applicability of the systems discussed in this paper.
The study and kinetic interpretation of electrode reactions was, from the early years of electrochemistry, dominated by processes occurring at electrodes with metallic conductivity. Only since the late 1950s and early 1960s has it been realized that semiconductor electrodes behave differently in many respects and offer new insights into the role played by the electronic properties of a solid in its electrochemical reactivity. The investigation of semiconductor electrodes has intensified the link between electrochemistry and solid state physics, has created a close connection to photochemistry and has profoundly improved the understanding of interfacial reactions. Selected examples are presented in this lecture.
A black trithiocyanato-ruthenium(II) terpyridyl complex where the terpyridyl ligand is substituted by three carboxyl groups in 4,4',4''-positions achieves very efficient panchromatic sensitization of nanocrystalline TiO2 solar cells over the whole visible range extending into the near-IR region up to 920 nm.
The synthesis and properties of several complexes of Ru(II) containing 4,4'-dicarboxy-2,2'-bipyridine (dcbpyH(2)), 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (bmipy), or 2,6-bis(1-methylbenzimidazol-2-yl)-4-phenylpyridine (ph-bmipy), and monodentate ligands (X(-) = Cl-, I-, NCS-, NCSe-, CN-) are reported. The introduction of the ambident ligands X(-) = NCS-, NCSe-, and CN- into the coordination sphere of [Ru(bmipy)(dcbpy)I](-) and cis-Ru(dcbpyH(2))(2)Cl-2 has been studied in situ via H-1 and C-13 NMR spectroscopy using C-13-enriched ligands X(-). Introduction of thiocyanate and selenocyanate initially yields the two possible linkage isomers in comparable amounts; prolonged reaction time converts the S-bound isomer and the Se-bound isomer to the N-bound isomers. The isoselenocyanate complex decomposes rapidly, yielding the cyano complex under loss of Se. The N-bound isothiocyanato complex K[Ru(bmipy)(dcbpy)(NCS)] was found to be an efficient sensitizer for nanocrystalline TiO2; the incident monochromatic photon-to-current efficiency (IPCE) is nearly quantitative at 520 nm. Introduction of a phenyl group in the 4-position of the 2,6-bis(1-methylbenzimidazol-2-yl)pyridine ligand gives a red-shifted absorption maximum for the corresponding phenylated K[Ru(ph-bmipy)(dcbpy)(NCS)] complex with an increased molar absorption coefficient for the MLCT maximum at 508 nm. At longer wavelengths above 620 nm, phenyl substitution does not enhance the absorption coefficients of the complex. Compared to that of K[Ru(bmipy)(dcbpy)(NCS)], the performance of the phenylated complex is reduced in a solar cell due to lower IPCE values. The visible spectra of the halide complexes K[Ru(bmipy)(dcbpy)X] (X(-) = Cl-, I-) show enhanced red response, but the complexes exhibit strongly reduced overall IPCE values. A comparison of the complexes to cis-Ru(dcbpyH(2))(2)(NCS)(2) is presented. Possible strategies for the design of more efficient sensitizers are discussed.
cis-X2Bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) complexes (X = Cl-, Br-, I-, CN-, and SCN-) were prepared and characterized with respect to their absorption, luminescence, and redox behavior. They act as efficient charge-transfer sensitizers for nanocrystalline TiO2 films (thickness 8-12 mum) of very high internal surface area (roughness factor ca. 1000), prepared by sintering of 15-30-nm colloidal titania particles on a conducting glass support. The performance of cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) (1) was found to be outstanding and is unmatched by any other known sensitizer. Nanocrystalline TiO2 films coated with a monolayer of 1 harvest visible light very-efficiently, their absorption threshold being around 800 nm. Conversion of incident photons into electric current is nearly quantitative over a large spectral range. These films were incorporated in a thin-layer regenerative solar cell equipped with a light-reflecting counter electrode. Short-circuit photocurrents exceeding 17 mA/cm2 were obtained in simulated AM 1.5 sunlight using lithium iodide/triiodide in acetonitrile or acetonitrile/3-methyl-2-oxazolidinone mixtures as redox electrolyte. The open-circuit photovoltage was 0.38 V and increased to 0.72 V by treating the dye-covered film with 4-tert-butylpyridine. A solar-to-electric energy conversion efficiency of 10% was attained with this system. The effect of temperature on the power output and long-term stability of the dye was also investigated. For the first time, a device based on a simple molecular light absorber attains a conversion efficiency commensurate with that of conventional silicon-based photovoltaic cells.
Transparent titanium dioxide membranes (thickness 2.7 μm) were prepared by sintering of 8-nm colloidal anatase particles on a conducting glass support. The dynamics of charge recombination following electron injection from the excited state of RuLâ (L = 2,2â²-bipyridine-4,4â²-dicarboxylic acid) into the conduction band of the semiconductor were examined under potentiostatic control of the electric field within the space charge layer of the membrane. Biasing the Fermi level of the TiOâ positive of the flat-band potential sharply reduced the recombination rate, a 1,000-fold decrease being associated with a potential change of only 300 mV. Photoelectrochemical experiments performed with the same RuLâ-loaded membrane in NaI-containing water show the onset of anodic photocurrent to occur in the same potential domain. Forward biasing of the membrane potential impairs photosensitized charge injection turning on the photoluminescence of the adsorbed sensitizer.
By using high surface area (roughness factor ca. 200) polycrystalline anatase films together with tris(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II), RuL/sub 3//sup 4 -/, as a sensitizer, the authors have achieved unprecedentedly high visible light to electric current conversion efficiencies in regenerative photoeletrochemical cells. Incident photon to current conversion efficiencies of 73% have been obtained at the wavelength of maximum absorption of the dye in the presence of iodide as an electron donor. Bromide is oxidized under the same conditions with an efficiency of 56%. A regenerative cell based on the Br/sub 2//By/sup -/ redox system gives a monochromatic light to power conversion efficiency of 12% with a fill factor of 74%. Preliminary results with polychromatic illumination are also presented.
+32.37 and 33.01 ppm, respectively. The deshielding of the boron nucleus in these species is consistent with a strained ring struc- ture.IO The Raman spectrum of 1 exhibits a strong line at 905 cm-I with satellites at 927 and 944 cd, assigned to the symmetric ring stretching of the BzOZ framework. These frequencies are about 100 cm-I higher than for related six-membered rings, Photolysis of 1 in the presence of trapping agents led to products which may arise from the intermediate oxoborane 2.12 Thus irradiation at 254 nm of a solution of 1 in tert-butyl methyl ketone produced the dioxaboretane 7,13 and similar photolysis in the presence of 2,2,4,4-tetramethyl-2,4-disila- 1-oxacyclopentane gave the product 814 (eq 5), both in nearly quantitative yields. RjB303.l'
To explore the binding properties of [Ru(phen)(2)dppz](2+) complex (phen = 1,10-phenanthroline, dppz = dipyrido[3,2-a:2',3'-c]phenazine) in a sequence-specific manner in DNA duplex, it was tethered through the dppz ligand to a central position as well as both at the 3'- and 5'-ends of oligodeoxyribonucleotide (ODN). The middle [Ru(phen)(2)dppz](2+)-ODN tethered was resolved and isolated as four pure diastereomers, while the 3'- or 5'-[Ru(phen)(2)dppz](2+)-ODNs were inseparable on RP-HPLC. Thermal stability of the (Ru(2+)-ODN).DNA duplexes is found to increase considerably (DeltaT(m) = 12.8-23.4 degrees C), depending upon the site of the covalent attachment of the tethered [Ru(phen)(2)dppz](2+) complex, or the chirality of the [Ru(phen)(2)dppz](2+)-linker tethered at the middle of the ODN, compared to the unlabeled counterpart. Gross differences in CD between the [Ru(phen)(2)dppz](2+)-tethered and the native DNA duplexes showed that the global duplex conformation of the former has considerably altered from the B-type, but is still recognized by DNase I. The thermal melting studies, CD measurements, as well as DNase I digestion data, are interpreted as a result of intercalation of the dppz moiety, which is realized by threading of the Ru(phen)(2) complex part through the DNA duplex core. DNase I footprinting with four diastereomerically pure middle ([Ru(phen)(2)dppz](2+)-ODN).DNA duplexes furthermore showed that the tethered [Ru(phen)(2)dppz](2+)-linker chirality dictates the stereochemical accessibility of various phosphodiester moieties (around the intercalation site) toward the cleavage reaction by the enzyme. The diastereomerically pure ruthenium-modified duplexes, with the well-defined pi-stack, will be useful to explore stereochemistry-dependent energy- and electron-transfer chemistry to understand oxidative damage to the DNA double helix as well as the long-range energy- and electron-transfer processes with DNA as a reactant.
ALTHOUGH the possibility of water photolysis has been investigated by many workers, a useful method has only now been developed. Because water is transparent to visible light it cannot be decomposed directly, but only by radiation with wavelengths shorter than 190 nm (ref. 1).