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...

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Durch Reaktion des Komplexes aus DMF und POCl3 mit 2‐Ethoxy‐ (II) bzw. 2‐Phenylinden (VIII), beide erhalten aus dem Indanon (I), werden die Glutaconaldehydderivate (III) bzw. (IX) mit o‐Phenylenbrücke in der konjugierten Kette erhalten.

UDC 535.37Conformations of He-jet-cooled trimethyl [(3-indole)ethoxy]silane (TIES) have been studied using a laser spectroscopy technique in combination with quantum-chemical computations. Six probable conformers of the molecule were computed, of which only two conformations were observed. Based on an analysis of fluorescence excitation spectra, fluorescence spectra, shapes of rotational band contours at the electronic S 0 -S 1 transition of TIES, and theoretical computations, the above conformers were assigned to steric structures. Twisted structures have the lowest energy due to intramolecular hydrogen bonds C-H⋅⋅⋅O< C Si between hydrogen atoms of methyl groups and an oxygen atom and C-H⋅⋅⋅π between H and the π-electron cloud of the indole ring.Introduction. The non-classical hydrogen bond, interaction between an H atom (bound to one of the electronegative C, O, or N atoms) and the π-electron cloud of an aromatic ring, has been widely studied in the last decade. Such weak non-covalent bonds are formed intramolecularly [1-3] or intermolecularly [4,5] in van-der-Waals complexes in biological systems. Weak H-bonds should be considered when examining molecular structures of fluxional molecules and their stabilization energies. Frequencies of purely electronic S 0 -S 1 -transitions of organic molecular structures vary from units to tens of inverse centimeters [1][2][3]. This makes it possible to use jet cooling to identify these conformers. Various methods of laser UV and IR spectroscopy are used in such investigations. The preferred structures can be determined when they are combined with modern quantum-chemical computation methods.Herein we analyze the molecular structures of trimethyl[(3-indole)ethoxy]silane (TIES) and examine the effect of an intramolecular H-bond on the stabilization energy of its conformers.Experimental. Fluorescence excitation and fluorescence spectra were measured using the automated spectrometry complex that was described before [6]. The carrier gas, He at a pressure of 2 atm, was fed into a prechamber heated to 400 K that contained saturated TIES vapor. The liquid organic compound was placed into capillaries (0.75 internal diameter, 30 mm long). The number of capillaries was selected so that the optimal luminescence signal was obtained. A pulsed supersonic stream was formed by flowing the gas mixture into the vacuum chamber through a round nozzle (diameter 0.7 mm). The cooled molecules were excited by the second harmonic of a frequency-tuned dye laser at distances of 19 and 10 mm from the nozzle for recording fluorescence excitation and fluorescence spectra, respectively. The dye laser was pumped by the second harmonic of a Nd-doped yttrium-aluminum garnet laser (LOTIS TII, LS-2134). The wavelengths of the first harmonic of the dye laser were calibrated using the fluorescence excitation spectrum of iodine vapor. Integral fluorescence was recorded using a Hamamatsu R928 photoelectron multiplier. A DFS-52 monochromator with a diffraction grating (2400 lines/mm) was used to study the fluores...

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