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Properties and characteristics of squarylium-based chemosensors for Hg2+
Abstract
A chemosensor based on symmetrical squarylium (SQ) dye, 2,4-bis((3,3-dimethylindolin-2-ylidene)methyl)cyclobutane-1,3-bis(olate), was synthesised and its cation-sensing properties in acetonitrile were investigated by UV–vis spectroscopy. Upon the addition of Hg2+, the solution of SQ dye showed clear colour change. The absorption studies also indicate a higher affinity of Hg2+ towards the formation of 2:1 complexes, which is in good agreement with the experimental results. The selective detection of Hg2+ of the symmetrical-SQ unit gave rise to a significant absorption decrease at λmax 650 in acetonitrile solution.
... In our earlier study, we have incessantly worked with the synthesis and determination of the optical properties of new rhodamine derivatives as chemosensors, which can potentially be utilized as a useful chromogens for the selective and quantitative detection of metal ions to the biological and environmental appli- cations [87,88]. In addition, we have recently reported the synthesis [89] and binding properties of SQ dye chemosensor which exhibited high selectivity for cyanide anion [90] and the cation sensing properties, especially showing highly selective absorption changes about Hg 2+ ions among the various metal ions [91] as presented in (Scheme 2). The pertained requirements and potential applications with this class of materials have promoted us to investigate the synthesis and to validate the chemosensor applications using SQ derivatives . ...
... 7 (A). NMR studies of symmetrical SQ dye were earlier reported by De- Yin Huang et al. [91] symmetrical SQ dye in CD 3 CN solvent (Supplementary informationFig. S3). ...
... In our previous study, we reported the synthesis and binding properties of a SQ [53] and iminium salt [54] chemosensors, which exhibited a high selectivity for cyanide anion. Very recently, we reported the cation sensing properties of our SQ chemosensor, which showed a selective change in absorption in the presence of mercury cations through "turn on" fluorescence intensity and a visual color change [55,56]. To the best of our knowledge, this sensor is one of the few SQ-based "turn on" fluorescent sensors [41,57,58], and the current work represents the first report on the use of a squaraine-rhodamine (SR) dye as a probe for the detection of mercury metal ion. ...
... Thus, high selectivity toward the probe is an advantage of chemodosimeters, making them useful for detecting Hg 2+ ions. However, only a few Hg 2+ chemodosimeters are currently available [13][14][15][16], and probes that exhibit Hg 2+ -triggered fluorescence enhancement have attracted particular attention [17,18]. ...
We report the design and synthesis of a novel rhodamine–pyridine derivative-based indicator for Hg2+ion determination. The indicator exhibited highly selective and sensitive colorimetric and “turn-on” fluo-rescent responses toward Hg2+ions based on the ring-opening mechanism of the rhodamine spirolactamin an acetonitrile:water (CH3CN:H2O) solution. The obvious change from colorless to pink upon the addi-tion of Hg2+could make it a suitable “naked eye” indicator for Hg2+. Finally, we proposed a reversiblering-opening mechanism (OFF–ON) of the rhodamine spirolactam induced by Hg2+binding and a 1:1stoichiometric structure between rhodamine–pyridine (RP) and Hg2+. More significantly, the RP–Hg2+complex exhibited a dual-channel chromo fluorogenic response to biologically important cysteine withhigh sensitivity and selectivity over other natural amino acids. The sensors display a remarkably Hg2+-selective colorless fluorescence with a yellowish-green color switch over a wide range of tested metalions.
A chemosensor is a synthetic chemical system which is capable of binding with an analyte in a selective and reversible manner followed by change in one or more properties of the system in the form of color or fluorescence or redox potentials. The choice of a chromophore has tremendous effect on these properties. The well established and indispensable role of metal ions in connection to their medicinal, biological and environmental concern makes their sensing one of the major research domains out of other domains including detection of anions, bio molecules, pesticides, explosives, etc. Therefore, the number of research articles is growing at a high rate dedicated to pave path for more reliable and sophisticated chemosensors. In this context, continuous compilation of research work is highly desirable (or acceptable) in order to generate a library of chromophores helping the budding researchers to access the present trends in limited (short) time. In this review, we have focused on colorimetric sensors for metal ions, viz. alkali and alkaline earth, Al³⁺, Cr³⁺, Mn²⁺, Fe³⁺/Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺/Cd²⁺, Hg²⁺, Ag⁺, Sn⁴⁺/Sn²⁺, Pd²⁺, Pb²⁺, Zr⁴⁺, Mo⁶⁺, due to their numerous advantages such as, easy detection without requiring sophisticated instruments, high selectivity and sensitivity in terms of different color change for different species, over other chemosensors. This work is a comprehensive survey of colorimetric sensors for metal ions developed in the years from 2011 to 2016 (>450 references).
Naphthalenic compounds are a rich resource for designers of fluorescent sensing/switching/logic systems. The degree of internal charge transfer (ICT) character in the fluorophore excited states can vary from negligible to substantial. Naphthalene-1,8;4,5-diimides (11–13), 1,8-naphthalimides (16) and 4-chloro-1,8-naphthalimides (15) are of the former type. The latter type is represented by the 4-alkylamino-1,8-naphthalimides (1). Whether ICT-based or not, these serve as the fluorophore in 'fluorophore-spacer-receptor' switching systems where PET holds sway until the receptor is bound to H +. On the other hand, 4-dialkylamino-1,8-naphthalimides (3–4) show modest H +-induced fluorescence switching unless the 4-dialkylamino group is a part of a small ring (5). Electrostatic destabilization of a non-emissive twisted internal charge transfer (ICT) excited state is the origin of this behaviour. An evolution to the non-emissive twisted ICT excited state is responsible for the weak emission of the model compound 6 (and related structures 7 and 8) across the pH range. Twisted ICT excited states are also implicated in the switch 9 and its model compound 10, which are based on the 6-dialkylamino-3H-benzimidazo[2,1-a]-benz[d,e]isoquinolin-3-one fluorophore.
Mercury is a toxic and hazardous metal that occurs naturally in the earth's crust. Natural phenomena such as erosion and volcanic eruptions, and anthropogenic activities like metal smelting and industrial production and use may lead to substantial contamination of the environment with mercury. Through consumption of mercury in food, the populations of many areas, particularly in the developing world, have been confronted with catastrophic outbreaks of mercury-induced diseases and mortality. Countries such as Japan, Iraq, Ghana, the Seychelles, and the Faroe Islands have faced such epidemics, which have unraveled the insidious and debilitating nature of mercury poisoning. Its creeping neurotoxicity is highly devastating, particularly in the central and peripheral nervous systems of children. Central nervous system defects and erethism as well as arrythmias, cardiomyopathies, and kidney damage have been associated with mercury exposure. Necrotizing bronchitis and pneumonitis arising from inhalation of mercury vapor can result in respiratory failure. Mercury is also considered a potent immunostimulant and -suppressant, depending on exposure dose and individual susceptibility, producing a number of pathologic sequelae including lymphoproliferation, hypergammaglobulinemia, and total systemic hyper- and hyporeactivities. In this review we discuss the sources of mercury and the potential for human exposure; its biogeochemical cycling in the environment; its systemic, immunotoxic, genotoxic/carcinogenic, and teratogenic health effects; and the dietary influences on its toxicity; as well as the important considerations in risk assessment and management of mercury poisoning.
Industrial processes introduce up to a million different pollutants into the atmosphere and the aquatic ecosystem. Heavy metals are one group of these substances, although not all of them are considered harmful to humans.The molecule of calixarene is a macrocycle used effectively in the complexation of the heavy metal pollutants (nickel, copper(II)…). The goal of this work is to condition a new chromogenic calix[4]arene molecule to elaborate an optical fiber sensor able to detect this type of pollutant. The light power increases when the concentration of the ion increases. The optimum pH for heavy metal ion detection is found to be 5. The influence of the unclad length on the response sensor is studied and the optimum length is found to be around 3 cm. The limit of detection reached is of the order of 1 μM, 10−3 μM and 10−4 μM for copper(II), cobalt(II) and cadmium(II) cations respectively.
Self-assembly of a squarylium dye containing an alkanethiol substituent on a gold surface is described. The self-assembled monolayers (SAMs) obtained were investigated by contact angle measurement and atomic force microscopy (AFM). Surface plasmon resonance (SPR) has been employed to investigate the interaction of the squarylium dye monolayer on gold with metal ions. A highly Cu2+ selective SPR sensing system was demonstrated with SAM for the squarylium dye on gold.
A squarylium dye carrying a monoazacrown moiety has been synthesized and characterized. The new azacrown-squarylium (ACSQ) dye 7 demonstrates sensitivity to Li+ complexation with spectroscopic changes in fluorescence. Complex formation of ACSQ with Cu2+ was also investigated by UV–Vis spectrometry.
A new dithiosquarylium (DTSQ) dye was examined as an electron transport material in organic EL devices. We fabricated the EL cell with poly(p-phenylene vinylene) (PPV) as the emission layer. DTSQ was found to be useful as a novel electron transport material. The EL device with DTSQ as the electron transport layer was more efficient than that with only the PPV layer.
The electrochromic properties of some squarylium dye (SQ) were studied by using BuOHCH2Cl2 (4:6/v:v) solution with Bu4NClO4 as supporting electrolyte. The electrochromic display (ECD) cell of these squarylium dyes coloured blue in open-circuit condition, but changed to a green colour at 1.41 ∼ 1.8 volt. At an applied voltage in the range higher than 2.1 volt, the absorbance at 480 nm and 630 nm decreases rapidly and the reversible colour change in open-circuit condition disappeared. The cyclic voltametric behaviour of the dyes was investigated and the first and second oxidation potentials measured. Decolouration rates in open-circuit were found to be first-order processes.
Various symmetrical and unsymmetrical squarylium dyes have been synthesized and characterized with the aid of IR spectroscopy and solvatochromism. The photofading of squarylium dyes has been investigated in solution and in polyvinylbutyral (PVB) film with carbon arc Fade-Ometer. The photostability of squarylium dyes increases with the electron-with-drawing power of substituent groups at the indoline moiety. The rates of photofading of these dyes were remarkably suppressed in the presence of hydroxycarboxylic acid metal salt, while the addition of UV-absorber afforded little retardation of the rate of fading.
The complex formation of squarylium (SQ) and dithiosquarylium (DTSQ) dyes with Cu2+ and Ag+ was investigated spectrophotometrically. Their absorption spectra showed cation selective spectral intensity changes in the presence of specific metal ions in CH2Cl2–CH3CN due to cation complexing. Highly selective ion sensing film optodes for the determination of two kinds of ions, Cu2+and Ag+, were prepared with plasticized PVC–PVAc–PVA membranes containing the SQ or DTSQ dye.
The organic electoluminescent diode (LED) with squarylium (Sq) dye-doped Alq3
changes color upon application of voltage (current). The luminescent color from the
organic LED changes from red (electroluminescence (EL) of Sq dye) at low voltage to
light green (EL of Alq3) at high voltage. We studied the EL efficiency and EL spectrum
of organic Sq-doped Alq3 LED with various doping positions in the emission layer.
Consequentially, it was clarified that Sq doping near TPD considerably reduced the
EL efficiency. The EL mechanism of the organic LED was concluded to be associated with
the energy transfer from the excited Alq3 to the guest dye and hole trapping of the guest dye in Alq3.
The crystal structure of a new dithiosquarylium dye (DTSQ), viz, 2,4-bis(1,3,3-trimethyl-2-indolinylidenemethyl) cyclobutenediylium-1,3-dithiolate, has been determined by X-ray crystallography. A crystal was grown from chloroform/ethylacetate (8:1/v:v) and found to exist in the monoclinic space group P21/n (no. 14). The molecule is roughly planar and adopts the trans conformation.
Squarylium dye containing a nitro group, absorbs at 676nm in chloroform and showed a bathochromic shift of 22nm in comparision to the unsubstituted analogue. The reaction between squaric acid and 2,3,3-trimethyl-5-nitroindolenine proceeded readily giving a product in 97% yield. Electrophotographic characteristic of negatively charged dual-layered photoreceptors with squarylium dyes for charge generation materials and five charge transport materials have been investigated. Photoreceptors that used squarylium dyes containing a nitro group, exhibited high sensitivity under light exposure.
The photovoltaic properties of Schottky barrier solar cells made from thin films (100–1000 Å) of the organic dye hydroxy squarylium have been studied. Amorphous and polycrystalline films, prepared by evaporation and solution casting, have strong absorption over the entire visible spectrum. The highest power conversion efficiency measured under AMO white light was 0.1% (0.14 mW/cm2 input intensity); this decreased to 0.02% at 135 mW/cm2. The decrease in η with intensity is characteristic of organic materials, but is usually much more pronounced. For 8500‐Å monochromatic light the quantum efficiency was as high as 2.3% and the conversion efficiency was 0.2% (1 mW/cm2).
A new “HCTH” generalized gradient approximation (GGA) functional is presented. Its 15 parameters have been refined against data from a training set containing 407 atomic and molecular systems. We believe that the much enhanced training set means that the new functional HCTH/407 has a much greater universality than previous GGA functionals. Statistical data is presented for the 407 set for the new functional, as well as other functionals. © 2001 American Institute of Physics.
A method for accurate and efficient local density functional calculations (LDF) on molecules is described and presented with results. The method, Dmol for short, uses fast convergent three‐dimensional numerical integrations to calculate the matrix elements occurring in the Ritz variation method. The flexibility of the integration technique opens the way to use the most efficient variational basis sets. A practical choice of numerical basis sets is shown with a built‐in capability to reach the LDF dissociation limit exactly. Dmol includes also an efficient, exact approach for calculating the electrostatic potential. Results on small molecules illustrate present accuracy and error properties of the method. Computational effort for this method grows to leading order with the cube of the molecule size. Except for the solution of an algebraic eigenvalue problem the method can be refined to quadratic growth for large molecules.
Recent extensions of the DMol3 local orbital density functional method for band structure calculations of insulating and metallic solids are described. Furthermore the method for calculating semilocal pseudopotential matrix elements and basis functions are detailed together with other unpublished parts of the methodology pertaining to gradient functionals and local orbital basis sets. The method is applied to calculations of the enthalpy of formation of a set of molecules and solids. We find that the present numerical localized basis sets yield improved results as compared to previous results for the same functionals. Enthalpies for the formation of H, N, O, F, Cl, and C, Si, S atoms from the thermodynamic reference states are calculated at the same level of theory. It is found that the performance in predicting molecular enthalpies of formation is markedly improved for the Perdew–Burke–Ernzerhof [Phys. Rev. Lett. 77, 3865 (1996)] functional. © 2000 American Institute of Physics.
A new class of dithiosquarylium dyes (DTSQ) has been synthesized by the reaction of squarylium dye (SQ) with Lawesson's reagent or P4S10. The λmax, of DTSQ dyes undergoes a bathochromic shift of about 25 nm compared with corresponding SQ dyes. The visible absorption spectra of DTSQ dyes are well accounted for by Pariser-Parr-Pople Molecular Orbital (PPP-MO) calculations. Electrophotographic characteristics of negatively charged dual layered photoreceptors with DTSQ for charge generation materials (CGM) and 1-phenyl-1,2,3,4-tetrahydroquinoline-6-carboxyaldehyde-1′,1′-diphenylhydrazone as a charge transport material (CTM) have been investigated. The photoreceptor that used DTSQs exhibited high photosensitivity at white light.
Representatives of a new class of unsymmetrical squarylium dyes containing a quinolylidene moiety have been synthesised and characterised. These dyes absorbed at a longer wavelength (11–50 nm) than the corresponding symmetrical squarylium dyes. The influence of the quinolylidene moiety on the absorption of these dyes was studied and compared with that calculated by the PPP-MO method. The photostability properties of the dyes were investigated in chloroform with a high-pressure mercury lamp. The aggregation of the unsymmetrical squarylium dyes were also studied in different DMSO/water solutions, including solutions with γ-cyclodextrin.
The syntheses of various squarylium dyes are reviewed in this paper. Possible applications of these dyes are also discussed, including their electrochromic, electroluminescence, electrophotographic and metal ion sensing properties.
A squarylium (SQ) dye was synthesized by the reaction between squaric acid and 2,3,3-trimethylindolenine and its anion sensing properties were investigated using absorption and emission spectroscopy. This chemosensor exhibited high selectivity for CN(-) as compared with F(-), CH(3)CO(2)(-), Br(-), H(2)PO(4)(-), Cl(-), and NO(3)(-) in acetonitrile, which was attributed to the formation of a 1:1 squarylium:CN(-) coordination complex, the formation of which was supported by the calculated geometry of the complex.
The need for selective and sensitive sensors able to monitor in real-time and real-space the concentration of analytes of biological, clinical, and environmental interest is nowadays generally accepted. Of the various kinds of chemosensors, luminescence-based chemosensors present many advantages, since they can take profit of the high sensitivity and versatility typical of photoluminescence spectroscopy. In this contest, special interest has been devoted to the development of luminescent chemosensors for transition metal ions, since some of them are present in biological systems in trace amounts and, at the same time, they all can represent an environmental concern when present in uncontrolled amounts. In this contribution we review the chemical systems able to act as luminescent chemosensors for this class of metal ions.
Aminosquarylium dyes(6a–d) were prepared by condensation of aminosquarates (3a–d) and 1-ethyl-2,3,3-trimethylindolenium iodide (5) and structure of dye 6 was discussed on the basis of IR and solvatochromism. A new aminosquarylium dye 6a absorbed at a longer wavelength (18 nm) than the corresponding squarylium dye 7. The light absorption characteristics of representative examples are well accounted for with the PPP-MO calculation. The photostability properties of dye 6d was also investigated in solution with a high pressure mercury lamp when iodine was replaced by benzene dithiol metal complex as a counter anion, the photochemical stability being better than that of dye 7.
Chemosensors find wide applications in many disciplines such as biochemistry, clinical and medical sciences, cell biology, analytical chemistry and environmental sciences. Aiming to develop new chemosensors for future applications, we have synthesised and studied many different species. We present here the latest luminescent chemosensors for transition metal ions studied in our laboratory. In the various systems active units and receptors are different as are the target ions: Zn2+, Ni2+, Cd2+, Hg2+, Co2+, Ag+ and Cu2+. In solution a good selectivity and affinity was observed and the binding is signalled in all cases by pronounced changes in the photophysical properties such as emission wavelength and intensity, and excited state lifetime of the inserted luminophore. The mechanism for signal transduction depends strongly on the chosen receptor and luminophore moieties, and has been investigated in detail by means of steady state and time resolved spectroscopy.
Several researchers conducted studies to demonstrate the use of fluoro- and chromogenic chemodosimeters for heavy metal ion detection in solution and biospecimens. They demonstrated that fluorescent chemodosimeters had emerged as as a research area of significant importance due to their potential in detecting heavy metal ions in solution and biospecimens. Chemodosimeters were used to detect an analyte through a highly selective and irreversible chemical reaction between the dosimeter molecule and the target analyte. This led to an observable signal that had an accumulative effect and was directly related to the concentration of the analyte. The chemodosimeter also provided signaling changes in absorption wavelength and color that were widely used as detection events, as they required only the use of cost-effective equipment or no equipment in some cases.
An overview of some of the latest efforts made at tracing metal imaging and offering a perspective of this rapidly evolving research field is presented. A number of significant microanalytical techniques are available for the in situ detection of trace metals in cells and tissues. Each offers specific advantages and disadvantages depending on the task to be performed. Synchrotron and focused ion-beam microscopic techniques offer the best combination of sensitivity and spatial resolution. It has been observed that fluorescent dyes offer significantly greater optical sensitivity and have the potential for observing biological processes at the single-molecule level as compared with chromogenic histochemical stains. These indicators have the potential to passively diffuse across cell membranes and are better suited for the noninvasive imaging of cation fluxes in living cells due to their smaller molecular size.
Chris Orvig (right) and Mike Abrams (left) have been close friends and colleagues for 20 years. After completing undergraduate degrees at McGill University and Bowdoin College, respectively, they were graduate students with Alan Davison at Massachusetts Institute of Technology where they completed their Ph.D. degrees in 1981 and 1983, respectively. After Chris completed an NSERC of Canada postdoctoral fellowhip with Kenneth N. Raymond at Berkeley, Chris and Mike were reunited in 1983-84 at McMaster University in the labs of the late Colin J. L. Lock, where Mike was a NATO postdoctoral fellow. In 1984, Chris joined the faculty in the Chemistry Department at the University of British Columbia, where he remains, and Mike joined Johnson Matthey where he rose to become Manager of Biomedical Research, Worldwide, before starting AnorMED (where he is President and CEO) in 1997 with some of his Johnson Matthey colleagues. Mike is also an adjunct professor in the Chemistry Department at UBC. Both Chris and Mike are deeply interested in medicinal inorganic chemistry and outdoor activities.
Squaraines belong to an important class of organic dyes with intense absorption and emission properties in the visible to near-IR wavelength range. The optical properties of squaraines, which are sensitive to the surrounding medium, make them ideal candidates to photophysists to study the excited-state properties and to material chemists for designing a variety of materials that are useful for wide-ranging applications. The present Account pertains to the recent developments in the materials chemistry of squaraines, highlighting our contributions to the study of squaraine-based near-IR dyes, low band gap polymers, and cation sensors.
Cited By (since 1996):713, Export Date: 18 October 2014