An investigation of squaraines as a new class of fluorophores with long-wavelength excitation and emission (original) (raw)
Photochemical properties of squarylium cyanine dyes
Photochemical & Photobiological Sciences, 2013
This study presents several new squarylium dyes derived from benzothiazole and benzoselenazole with several structural variations, namely the nature of the heteroaromatic ring and the length of the N,N'-dialkyl groups. Before being investigated in connection with their effect on living cells and/or tissues, these novel compounds were characterized, namely with respect to the determination of their main photophysical parameters. Therefore, a study of the ground state absorption, fluorescence emission (quantum yields and lifetimes) and singlet oxygen generation quantum yields was performed for all the compounds synthesized in order to evaluate their efficiency as photosensitizers. An increase of the alkyl chain length from ethyl to hexyl did not produce a clear change in the fluorescence quantum yields, showing no influence on the photoisomerization process. Heavy atom inclusion (Se instead of S) enhanced the singlet oxygen generation efficiency and decreased the intensity of the fluorescence emission. The external heavy atom effect (I − as a counterion instead of CF 3 SO 3 −) produced a significant increase in the singlet oxygen formation quantum yield (about 20%). Transient absorption studies in aerated and oxygen free samples revealed that the photoisomerization process, which could compete with the triplet state formation for all dyes in solution, is a negligible pathway for the excited state deactivation, in accordance with the rigidity introduced by the squaric ring into the polymethine chain of the dye, both in chloroform and ethanol. However, in the case of the chloroform solution a new transient was detected in air equilibrated solutions, resulting from a reaction of the excited squarylium dye in the singlet state with CHCl 3˙, and assigned to the radical cation (SQ +˙) of the dye.
Fluorescent properties of cyanine dyes as a matter of the environment
Research Square (Research Square), 2023
In non-viscous aqueous solutions, the cyanine uorescent dyes Cy3 and Cy5 have rather low uorescence e ciency and short excited state lifetimes due to their structural features. In this work, we investigated the effect of solubility and rotational degrees of freedom on the uorescence e ciency of Cy3 and Cy5 in several ways. We compared the uorescence e ciencies of two cyanine dyes sCy3 and sCy5 with the introduction of a sulfonyl substituent in the aromatic ring as well as covalently bound to T10 oligonucleotides. The results show that because of the different lengths of the polymethine chains between the aromatic rings of the dyes, cis-trans-isomerization has a much greater effect on the Cy3 molecule than on the Cy5 molecule, while the effect of aggregation is also signi cant.
Analytica Chimica Acta, 2006
A series of ring-substituted squaraines absorbing and emitting in the red and NIR spectral region was synthesized and their spectral and photophysical properties (quantum yields, fluorescence lifetimes) and photostabilities were measured and compared to Cy5, a commonly used fluorescent label. The absorption maxima in aqueous media were found to be between 628 and 667 nm and the emission maxima are between 642 and 685 nm. Squaraine dyes exhibit high extinction coefficients (163,000-265,000 M −1 cm −1 ) and lower quantum yields (2-7%) in aqueous buffer but high quantum yields (up to 45%) and long fluorescence lifetimes (up to 3.3 ns) in presence of BSA. Dicyanomethylene-and thio-substituted squaraines exhibit an additional absorption around 400 nm with extinction coefficients between 21,500 and 44,500 M −1 cm −1 . These dyes are excitable not only with red but also with blue diode lasers or light emitting diodes. Due to the favourable spectral and photophysical properties these dyes can be used as fluorescent probes and labels for intensity-and fluorescence lifetime-based biomedical applications.
Novel quinone cyanine dyes: synthesis and spectral studies
Dyes and pigments, 2002
Novel dimethine, bis dimethine and tetramethine cyanine dyes derived from benzo [4,5-b; 4 0 ,5 0-b 0 ] bis furo, thieno and pyrrolo-4,8-dione were prepared. The electronic visible absorption spectra of the dyes were examined in 95% ethanol. Structural confirmation is carried out by elemental analysis, IR and 1 H NMR spectral data.
The synthesis and characterization of novel, aza-substituted squarylium cyanine dyes
Dyes and Pigments, 2009
Several squarylium cyanine dyes derived from benzothiazole, benzoselenazole and quinoline were synthesised and the central four member ring functionalized by substitution of one of the oxygen atoms by benzylamine, aniline, 3-iodoaniline, N,N-dimethylhydrazine and 2-aminosulfonic acid groups. All of the ensuing, novel aza-substituted dyes displayed strong absorption within the range 651-709 nm.
Fluorescence lifetime properties of near-infrared cyanine dyes in relation to their structures
Journal of Photochemistry and Photobiology A: Chemistry, 2008
Structurally diverse near-infrared (NIR) absorbing polymethine dyes were prepared and their fluorescence lifetimes (FLT) were evaluated in relation to their structural features. Comparative FLT analysis based on the modification of methine chain length and heterocyclic system showed that indolium or benz[e]indolium heptamethine dyes exhibited longer FLT than the benz[c,d]indolium trimethine dye. Modification of heterocyclic system alone with an intact chain length showed that indolium-based heptamethine dyes showed approximately 30% longer FLT than the benz[e] indolium-based dyes. In general, the FLT of polymethine dyes increased from polar to non-polar solvents. In addition, correlation study between the theoretical and the experimental FLT for indocyanine green (ICG) suggests that the lack of structural rigidity for these cyanine dyes is primarily responsible for the loss of the excited state energy via non-radiative pathway.
SYNTHESIS OF CYANINE DYES CONTAINING QUINOLINIUM HALIDE AND INVESTIGATION OF FLUORESCENCE PROPERTIES
In this study, seven synergists were prepared to improve the contrast ratio in blue color filters derived from cyanine by quenching fluorescence. Improving contrast ratio of LCD color filters, therefore, requires the use of the colorant that can quench the fluorescence without also influencing the color. The colorant must also to be soluble in commercial solvent and stable on typical thermal conditions in the manufacturing process. Four synergists, were prepared in this study, they had absorption maxima of approximately 570~620nm and quenched fluorescence by more than 24%. The synergists increased the contrast ratio by about 30%, due to effective quenching of the fluorescence from the blue color filter, without changing the chromaticity diagram values.
Squaraine Dye as an Exciton Trap for Cyanine J-Aggregates in a Solution
The diindolenine derivative of squaraine dye Sq-2Me has been used as an exciton energy trap (an energy acceptor) for amphi-PIC J-aggregates in a solution. Using the modified Stern-Volmer equation, parameters of the energy transfer have been obtained. It has been revealed that 50% of J-aggregate luminescence is quenched in a binary DMF/water solution at the ratio trap/amphi-PIC) 1:80 that corresponds to the exciton migration over 20 delocalization segments within the J-aggregate.
Bioorganic & medicinal chemistry, 2017
New unsymmetrical aminosquarylium cyanine dyes were synthesized and their potential as photosensitizers evaluated. New dyes, derived from benzothiazole and quinoline, were prepared by nucleophilic substitution of the corresponding O-methylated, the key intermediate that was obtained by methylation with CF3SO3CH3 of the related zwitterionic unsymmetrical dye, with ammonia and methylamine, respectively. All three news dyes herein described displayed intense and narrow bands in the Vis/NIR region (693-714nm) and their singlet oxygen formation quantum yields ranged from 0.03 to 0.05. In vitro toxicity, in Caco-2 and HepG2 cells, indicated that dark toxicity was absent for concentrations up to 5µM (for the less active dye) or up to 1µM (for the two more active dyes). The three dyes present potential as photosensitizers, differing in irradiation conditions and period of incubation in the presence of irradiated dye. The less active dye needs a longer irradiation period to exhibit phototoxi...
1,3-Bis(phenylamino)squaraine – Photophysical and photochemical properties
Dyes and Pigments, 2016
A novel squarylium dye possessing donorepeacceptor structure that features a fixed imine phenyl ring as an electron donor and 3,4-dihydroxycyclobut-3-ene-1,2-dione moiety as an electron acceptor was synthesized. The structure of the dye was elucidated by means of NMR and IR spectroscopy and elemental analysis. The compound was studied using steady-state absorption and emission spectroscopy, as well as the time-resolved spectroscopy. The measurements were carried out in solvents of different polarity. The dye absorbs in the visible light region about 400 nm and emits light with low fluorescence quantum yield, below 1 Â 10 À3 M. An increases polarity of solvent results in a blue-shift of absorption band and red-shift of emission band, respectively. The rate constants of radiative and non-radiative deactivation of excited state depend on the viscosity of solvent used. The bimolecular quenching of excited singlet state of squaraine depends on the rate of diffusion process.
A Long-Wavelength Fluorescent Squarylium Cyanine Dye
2012
Fluorescence sensing of saccharides and glycoproteins using a boronic acid functionalized squarylium cyanine dye (-SQ-BA‖) is characterized in terms of synthetic, fluorometric, thermodynamic and kinetic parameters. In our previous work, this newly synthesized dye was successfully applied to the separation and quantification of Gram-positive bacteria by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF); however, the fundamental properties of the dye and its saccharide complexes still required elucidation, as presented in this paper. The dye itself forms nonemissive, soluble aggregates in aqueous solution. With the addition of a monosaccharide, the dye aggregate dissociates to form an emissive monomer accompanied by the formation of a cyclic cis-diol ester with long-wavelength emission ( ex = 630 nm, em = 660 nm). A very large fluorescence enhancement factor of 18× was observed for the sensing dye as a fructose complex at pH 10, yielding a limit of detection of 10 M fructose. The relative order of fluorescence enhancement of SQ-BA with other monosaccharides was found to be: fructose > ribose > arabinose ≈ galactose > xylose > mannose > rhamnose > fucose ≈ glucose; and apparent affinity constants of 10 2.80 , 10 2.08 and 10 0.86 M −1 were determined for fructose,
Materials
Photodynamic therapy is a medical modality developed for the treatment of several diseases of oncological and non-oncological etiology that requires the presence of a photosensitizer, light and molecular oxygen, which combined will trigger physicochemical reactions responsible for reactive oxygen species production. Given the scarcity of photosensitizers that exhibit desirable characteristics for its potential application in this therapeutic strategy, the main aims of this work were the study of the photophysical and photochemical properties and the photobiological activity of several dicyanomethylene squaraine cyanine dyes. Thus, herein, the study of their aggregation character, photobleaching and singlet oxygen production ability, and the further application of the previously synthesized dyes in Caco-2 and HepG2 cancer cell lines, to evaluate their phototherapeutic effects, are described. Dicyanomethylene squaraine dyes exhibited moderate light-stability and, despite the low singl...
Molecules (Basel, Switzerland), 2018
Heptamethine cyanine dyes are a class of near infrared fluorescence (NIRF) probes of great interest in bioanalytical and imaging applications due to their modifiability, allowing them to be tailored for particular applications. Generally, modifications at the -position of these dyes are achieved through Suzuki-Miyaura C-C coupling and S1 nucleophilic substitution of the chlorine atom at the -position of the dye. Herein, a series of 15 phenyl-substituted heptamethine cyanines was synthesized utilizing a modified dianil linker. Their optical properties, including molar absorptivity, fluorescence, Stokes shift, and quantum yield were measured. The HSA binding affinities of two representative compounds were measured and compared to that of a series of trimethine cyanines previously synthesized by our lab. The results indicate that the binding of these compounds to HSA is not only dependent on hydrophobicity, but may also be dependent on steric interferences in the binding site and struc...
The synthesis and spectroscopic studies of new aniline-based squarylium dyes
Dyes and Pigments, 2016
The synthesis and spectroscopic properties of series of new anilineebased squarine dyes have been presented. The effect of solvent polarity, hydrogen bonding and substituent on spectroscopic properties of 1,3-bis(phenylamino)squarine (SQG1), 1,3-bis(4-bromophenylamino)squarine (SQG2), 1,3-bis(4ethylphenylamino)squarine (SQG3), 1,3-bis(4-ethoxyphenylamino)squarine (SQG4), 1,3-bis(4nitrophenylamino)squarine (SQG5), 1,3-bis(4-chlorophenylamino)squarine (SQG6), 1,3-bis(4iodophenylamino)squarine (SQG7), 1,3-bis(4-aminobenzosulfo)squarine (SQG8) 1,3-bis(4methylphenylamino)squarine (SQG9) 1,3-bis(4-hydroxyphenylamino)squarine (SQK1) in ten selected solvents were studied.
Materials
Photodynamic therapy is an innovative treatment approach broadly directed towards oncological diseases. Its applicability and efficiency are closely related to the interaction of three main components, namely a photosensitizer, light and molecular triplet oxygen, which should drive cell death. Recently, several studies have demonstrated that squaraine cyanine dyes have a set of photophysical and photochemical properties that have made of these compounds’ potential photosensitizers for this therapeutic modality. In the present research work, we describe the synthesis and characterization of four quinoline- and benzoselenazole-derived unsymmetrical squaraine cyanine dyes. Except for the precursor of aminosquaraine dyes, i.e., O-methylated derivative, all dyes were evaluated for their behavior and absorption capacity in different organic and aqueous solvents, their ability to form singlet oxygen, their light-stability, and in vitro phototherapeutic effects against two human breast canc...
International Journal of Organic Chemistry, 2018
Cyanine dyes of zero/bis-zero methine incorporating imidazo(1,2-a)Pyridine (quinoline) or pyrazino(1,2-a)pyridine (quinoline) with stable C-N bond were synthesized using keto-oxime methylene Clink heterocyclic quaternary salts [1-phenyl-3-methyl-pyrazolino-4-keto-oxime-α-methylene-bis-pyridin-(quin oin)-1(4)-di-ium-iodide(ethiodide) salts and 1-phenyl-3-methyl-pyrazolino-4-ketooxime-α-methylene-N-2-methyl-bis pyridin (quinoin)-1(4)-di-iumiodide(ethiodide) salts]. Such heterocyclic precursors and related dyes were identified by elemental and spectral analyses. The absorption spectra properties of such dyes were investigated in 95% Ethanol to attempt and throw some light on the influence of such new heterocyclic nuclei and to compare or evaluate spectral behaviors. The absorption spectra of dyes in different pure solvents were examined in the visible region showing solvatochromism and the colour changes of dyes with solvents having different polarities. This permits a selection of the optimal solvent (fractional solvent) when such dyes are applied as photosensitizers. The spectral behavior of some selected newly synthesized cyanine dyes is observed in mixed solvents of different polarities and progressively increasing quantities of one solvent over the other were studied and showed an increase in the absorbance of CT band with increasing proportion of that solvent. Evidence for hydrogen bond formation between the solute molecules and solvent molecules allows measurement of certain energies such as hydrogen bonding, orientation, and free energies.