We present the results of a study of the spectral luminescence properties of three groups of indotricarbocyanine dyes, each of which is formed from compounds with the same cation and different anions. In high-polarity solvents, in the absorption and emission spectra of the dyes we see one type of center; in low-polarity solvents, due to the presence of different ionic forms of the dyes (free ions, contact ion pairs), we observe either one type or two types of centers. By analysis of the luminescence of molecular oxygen in the 1.27 µm spectral region, we determined the efficiency of photosensitization of 1 O 2 formation by dyes in deuterated solvents. We have shown that in low-polarity solvents, the yield for singlet oxygen generation is higher for indotricarbocyanine dyes which are found in the contact ion pair state and which also contain a heavy atom (I) in the anion. We have observed that an increase in the fraction of contact ion pairs in solution as the dye concentration increases or when an additional salt is introduced leads to an increase in the quantum yield for generation of singlet oxygen. In polar deuterated acetonitrile, the counterion has no effect on the efficiency of photosensitization of oxygen by the dyes.Introduction. Most polymethine dyes are salts whose molecules in solutions can be found in the form of an equilibrium mixture of several types of ionic forms (free ions, contact and solvent-separated ion pairs) [1]. The equilibrium between these forms is shifted toward an increase in the fraction of one form when the temperature and the nature of the solvent are varied, when the anion is substituted, and when ionic and solvating additives are added to the solution. The state of the ionic equilibrium in solutions has an effect on the processes of dissipation of the electronic excitation energy in the polymethine dye molecules. The fluorescence quantum yield and the fluorescence lifetime of the polymethine dye molecules decrease symbatically with strengthening of the anion-cation interactions [2, 3]. In the ion pairs, the probabilities of torsional vibrations in the polymethine chain are higher and the yield for photoisomerization of the molecules is higher; the degree of vibronic interactions and the probabilities of rotation about bonds are higher as more stable ion pairs are formed [4][5][6].Despite the significant number of publications devoted to study of the photophysical properties of polymethine dyes in different types of solvents, due attention has not been paid to the effect of the state of ionic equilibria on the efficiency of singlet oxygen generation by polymethine dyes. At the same time, such a study is important from both a scientific and an applied viewpoint. The applied importance is due to prospects for using these dyes for photochemotherapy of cancer and as biological fluorescent labels [7][8][9], and also because in biological structures, their molecules are mainly found in the form of contact ion pairs [10]. In this case, the efficiency of polymethine dyes as photosensitizers...
UDC 535.34Spectral-kinetic and photochemical properties of HITC dye with iodide and perchlorate counterions have been studied in environments where the dye molecules exist in different ionic forms. In ethanol, the dye molecules exist as free ions; in dichlorobenzene, as contact ion pairs. Superfast transformation of non-stationary spectra in an HITC dye bleaching band is found. The observed effects are interpreted within the framework of concepts on "burning out" a notch in the contour of a non-uniformly widened vibronic band of S 0 → S 1 -absorption. Qualitative differences in recorded absorption spectra from the dye excited electronic states for weakly and highly polar solvents are found. It is shown that the observed differences are caused by superfast charge transfer in the contact ion pairs that results in the formation of free radicals.
We present results of experimental and theoretical studies of the optical characteristics of a new indotricarbocyanine dye that is capable of effectively limiting the power of laser radiation in the visible spectral range. The spectral-luminescent and energy characteristics of the dye molecules and their absorption spectra from the excited state with nanosecond resolution are investigated experimentally. Quantum-chemical methods are used to calculate electronic absorption spectra from the ground (S 0 → S n ) and excited (S 1 → S n ) states and to determine the nature of electronic states of the molecule and the rate constants of intramolecular photophysical processes. The results of the theoretical research agree with experimental data. It is shown that the investigated dye has singlet-singlet absorption at 400-600 nm. Nonlinear absorption of the dye upon excitation by radiation of the second harmonic of a Nd:YAG laser is studied by z-scanning with an open diaphragm. The ratio of dye absorption cross sections from the excited and ground states at 532 nm is determined in the framework of a three-level model. The results are compared with those for previously studied compounds.Introduction. Polymethine dyes (PD) are broadly used in various branches of science and technology, e.g., in the photographic industry as photosensitizers [1], in biology and medicine as fluorescent markers and materials for photochemotherapy [2][3][4], in solar cells [5][6][7] and quantum electronics as passive gates, active media for tunable lasers, and nonlinear materials [8-10], etc. Recently the nonlinear optical properties of PD [11][12][13][14][15] have become especially interesting due to the search for new nonlinear materials for application as limiters of laser radiation power (nonlinear limiters) in the visible spectral region [13,16,17]. The properties of nonlinear optical materials based on organic dyes must satisfy several requirements in order to be highly efficient [18][19][20][21]. A high attenuation coefficient for laser radiation is one of the main parameters for optical limiters. In addition, there must be a low threshold and activation time, a broad dynamic range, high linear transmission in a broad spectral range, and, finally, a long operational lifetime for the active medium. PD in solutions satisfy most of these requirements. Therefore, the search for molecular structures in this class of organic molecules and comprehensive investigations of the optical properties of the most promising compounds used as the active medium of limiters are extremely timely.The limiting properties of solutions of the indotricarbocyanine dye 2-{7-[1,3,5-trimethyl-3-ethyl-2-(1H)-indoliniden]-4-chloro-3,5-trimethylene-1,3,5-heptatrien-1-yl}-1,3,5-trimethyl-3-ethylindolium perchlorate (PD 7098) were previously studied upon excitation by nanosecond pulses of second harmonic radiation from a Nd:YAG laser (532 nm) [21]. Quantum-chemical calculations and experimental investigations of the photophysical properties of this dye were carried out in o...
We have established that the shape and position of the maximum in the fluorescence spectrum of an indotricarbocyanine dye in tumor and normal tissues in vivo change over time after intravenous injection of the dye. Based on analysis of the spectral properties of the dye in vivo and in blood plasma, the dependence of the properties on the time since injection has shown that in the living body, the environment of the dye molecule changes as the photosensitizer goes from the skin into the tissue. We have established that in tissues in vivo, the dye molecules are localized in a region with low dielectric constant of the medium. We have shown that the change in the ratio of the concentrations of the different forms of hemoglobin in the blood has an effect on the absorption and shape of the fluorescence spectrum of the dye in tissues in vivo. Introduction.Polymethine dyes (PDs) are promising for use as photosensitizers for photochemotherapy (also called photodynamic therapy, PDT) [1]. This is first of all due to the presence of absorption bands in their spectra in a range in which biological tissues have greatest transparency (the phototherapeutic window) [2]. For a number of dyes in this class, high photoactivity was found in experiments on cell cultures and also on animals with tumors [1, 3, 4]. The prospects for using a specific photosensitizer mainly depend on how efficiently the molecules in the excited state can generate active intermediates. The probabilities of intramolecular processes for dissipation of the electronic excitation energy for tricarbocyanine dyes depend on the nature of the surrounding molecules [5]. In low-polarity organic solvents, cationic PDs may be found in the form of ions or a mixture of several types of ion pairs [6]. As shown in [7], cationic PDs in a HeLa cell culture are localized in a region with low dielectric constant, and are found mainly in the contact ion pair state. The nature of the environment of the PD molecules in biological tissues in vivo has not been studied to date.In this paper, we present the results of a study of the spectral luminescence properties of a symmetric indotricarbocyanine dye in a culture of HeLa tumor cells and in tissues in vivo in animals with tumors.Objects and Methods of Investigation. As the object of investigation, we used an indotricarbocyanine dye synthesized in the spectroscopy laboratory of the A. N. Sevchenko Research Institute of Applied Physical Problems: 2-{7-[3-methyl-3-ethyl-1-trimethylenecarbo-(6-O-D-glucosyl)-2(1H)-indolenylidene]-4-chloro-3,5-(O-phenyleno)-1,3,5-hexatrien-1-yl}-3-methyl-3-ethyl-1-trimethylenecarbo-(6-O-D-glucosyl)indolenylium bromide (PD1).In vivo experiments were conducted on mongrel white rats with subcutaneously grafted tumors of the sarcoma 45 (S-45) and sarcoma M1 (SM-1) strains. We used a group of 6-8 animals for the studies. The drug was injected intravenously in the ratio of 1-5 mg per kg of the animal's weight. The fluorescence spectra of PD1 in vivo was recorded using a spectrometer developed at the A. N. Sevc...
As demonstrated by the performed studies, the molecules of tricarbocyanine dye in vivo are localized in the lowpermittivity region of the medium, predominantly in the form of contact ion pairs. Comparison of the experimental data and numerical simulation results has revealed that deformation of the dye fluorescence spectrum upon photochemotherapy is due to an increased percentage of methemoglobin (up to 50%) in the total hemoglobin concentration of a tumor tissue. A change in the photosensitizer fluorescence spectrum is observed in the area of a tumor, where laser radiation affects necrosis of the tissues. An analysis of the spectral data enables one to predict a depth and extent of the developed tumor necrosis. With the use of spectral methods, the treatment effectiveness may be optimized by the proper selection of an optimum dose and power density for photoexposure in the process of chemotherapy, with due regard for the character of pathology and individual features of a patient.
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