Structure and physicochemical properties of cation polymethine dyes in Langmuir-Blodgett films

The physicochemical properties of monomolecular layers of amphiphilic cation polymethine dyes (i.e., thia- and oxacarbocyanines) on the surface of a water subphase are studied along with the conditions of Langmuir-Blodgett (LB) film preparation. The area occupied by one dye molecule in the liquid-stretched and liquid-condensed states of a monolayer is determined. Based on a comparison of experimental and theoretically calculated areas, the nature of dye packing in monolayers is studied by means of molecular mechanics using data from conformation analysis. The spectral and luminescent properties of cationic polymethine dyes in various media are investigated. Excimer fluorescence is observed in LB films. The excimers in LB films are found to arise not from monomers but from dye dimers. A possible mechanism of their formation is considered.     

Correlation of certain physicochemical parameters of polyconjugated systems

Journal of Structural Chemistry -     

Azoles and azines

The dipole moments of 2-aryl-4-chloro-6-oxo-1,3-thiazines and 2-aryl-4-chloro-5-formyl-6-oxo-1,3-thiazines (Ar=C₆H₅, C₆H₅Cl-p, C₆H₅CH₃-p) were determined experimentally in benzene and calculated by the additive scheme with the vector method, as well as by the PPDP/2 method. Comparison of the data obtained with the calculated data showed that the formyl group is taken out of the plane of the thiazine ring.For Communication 64, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 272–275, February, 1988.     

Synthesis and physicochemical properties of melam

Fusing melamine with 2, 4-diamino-6-chloro-s-triazine gives melam. From its UV and IR spectra, it is assigned structure II. Thermographic studies showed that melam is not an intermediate product, but a side product, of thermal deamination of melamine.     

Synthesis and physicochemical properties of metallobacteriochlorins

Access to metallobacteriochlorins is essential for investigation of a wide variety of fundamental photochemical processes, yet relatively few synthetic metallobacteriochlorins have been prepared. Members of a set of synthetic bacteriochlorins bearing 0-4 carbonyl groups (1, 2, or 4 carboethoxy substituents, or an annulated imide moiety) were examined under two conditions: (i) standard conditions for zincation of porphyrins [Zn(OAc)(2)·2H(2)O in N,N-dimethylformamide (DMF) at 60-80 °C], and (ii) treatment in tetrahydrofuran (THF) with a strong base [e.g., NaH or lithium diisopropylamide (LDA)] followed by a metal reagent MX(n). Zincation of bacteriochlorins that bear 2-4 carbonyl groups proceeded under the former method whereas those with 0-2 carbonyl groups proceeded with NaH or LDA/THF followed by Zn(OTf)(2). The scope of metalation (via NaH or LDA in THF) is as follows: (a) for bacteriochlorins that bear two electron-releasing aryl groups, M = Cu, Zn, Pd, and InCl (but not Mg, Al, Ni, Sn, or Au); (b) for bacteriochlorins that bear two carboethoxy groups, M = Ni, Cu, Zn, Pd, Cd, InCl, and Sn (but not Mg, Al, or Au); and (c) a bacteriochlorin with four carboethoxy groups was metalated with Mg (other metals were not examined). Altogether, 15 metallobacteriochlorins were isolated and characterized. Single-crystal X-ray analysis of 8,8,18,18-tetramethylbacteriochlorin reveals the core geometry provided by the four nitrogen atoms is rectangular; the difference in length of the two sides is ～0.08 ?. Electronic characteristics of (metal-free) bacteriochlorins were probed through electrochemical measurements along with density functional theory calculation of the energies of the frontier molecular orbitals. The photophysical properties (fluorescence yields, triplet yields, singlet and triplet excited-state lifetimes) of the zinc bacteriochlorins are generally similar to those of the metal-free analogues, and to those of the native chromophores bacteriochlorophyll a and bacteriopheophytin a. The availability of diverse metallobacteriochlorins should prove useful in a variety of fundamental photochemical studies and applications.     

Quantum-chemical investigation of certain physicochemical properties of C-nitro-1,2,3-triazole and N-alkyl-4(5)-nitro-1,2,3-triazoles

Quantum-chemical calculations have been carried out on molecular electrostatic potentials, proton affinity in the gas phase, gas phase basicity, and pK _BH+ values in aqueous solution for C-nitro- and N-alkyl-4(5)-nitro-1,2,3-triazoles, and the relative stability of the isomeric N-alkyl-4(5)-nitrotriazoles (alkyl = Me, Et, i-Pr, t-Bu) in the gas phase and in aqueous solution. For all the studied substances in the gas phase the 2H-tautomer and the N(2)-isomers were considerably more stable than the corresponding N(1) compounds, and the 3H-tautomer and N(3)-isomer were the least stable. In aqueous solution 1- and 3-isomers had close values of energies, but in the case of C-nitro-1,2,3-triazole the 1H form became even more stable than the 2H-form. It was established which ring nitrogen atoms of 1,2,3-triazoles are protonated in the gas phase and in solution. The obtained data correlate well with the results of experimental investigations on the alkylation of 1,2,3-triazoles in acidic and basic media and of the experimental investigation on the alkylation of C-nitro-1,2,3-triazoles with diethyl sulfate carried out in the present work. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1816–1828, December, 2008.     

Structure and some physicochemical properties of carbon and silicon phases with a LA3 diamond-like lattice

The structures and properties of two diamond-like C-LA3 and Si-LA3 phases with crystallographically equivalent atomic sites are calculated by density functional theory with the exchange-correlation potential in the generalized gradient approximation (DFT-GGA). For these phases the structural characteristics, cohesion energies, densities of states, and bulk moduli are determined and powder diffraction patterns are calculated. It is found that the cohesion energies, band gaps, and bulk moduli of C-LA3 and Si-LA3 phases are smaller than the corresponding values of cubic diamond and silicon. Possible methods to obtain experimentally diamond-like C-LA3 and Si-LA3 phases are also analyzed in the paper.     

Synthesis and physicochemical properties of cationic starches

The reaction kinetics of an aqueous suspension of potato starch, various amounts of NaOH, and cationic 3-chloro-2-hydroxypropyltrimethylammonium (chloride) were studied in detail. It was found that the compositions of the sparsely substituted cationic starch ethers and the efficiency of the reaction depended strongly on the ratio of components in the alkylating mixture. The physicochemical properties of the synthesized samples were studied using chemical analysis, scanning electron microscopy, x-ray structure analysis, and thermogravimetry. It was shown that the temperature regime of the reaction had a determining influence on the thermal stability and structural changes of the cationic starch derivative.     

Synthesis and physicochemical properties of girded porphyrins

-Alkyl-substituted 5,15-diphenylporphyrins are synthesized, whose phenyl rings are connected through the ortho positions by bridging groups of various length. The resulting porphyrins were characterized by the electronic absorption and ¹H NMR spectra, and their structure was calculated by the molecular mechanics method. The kinetics of complex formation of the synthesized porphyrins with copper(II) acetate in acetic acid and pyridine depend on the degree of shielding of the reaction center in the tetrapyrrole ligand and its planarity.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1733–1738.Original Russian Text Copyright © 2004 by Kuvshinova, Pukhovskaya, Semeikin, Golubchikov.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis of trichloromethyl-substituted azines from dichloromethyl-substituted azines and carbon tetrachloride under interphase catalysis conditions

The reactions of 2- and 3-dichloromethylpyridines and dichloromethylpyrazine with carbon tetrachloride in the presence of aqueous or solid alkali and an interphase catalyst lead to the corresponding trichloromethyl-substituted azines. The CCl₄-solid KOH-18-crown-6 system, in the use of which trichloromethyl-substituted heterocycles were obtained in preparative yields, was the most effective.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 50–53, January, 1990.     

Azoles and azines. 62. Structure of 2-aryl-1,3-oxazine-4,6-diones

¹H,¹³C NMR, IR, and UV spectra have been studied for solutions of a number of potentially tautomeric 2-aryl-1,3-oxazine-4,6-diones and their 5-methyl substituted analogs with variation of substituent at the para position of the benzene ring, as well as compounds with a fixed structure that simulates possible tautomeric forms. The data have been compared with the results of quantum chemical calculations carried out in SSO MO LCAO approximation by the CNO, CNDO/2, and MPNDO/3 methods. In DMSO and THF solution the test compounds exist predominantly as 2-aryl-4-hydroxy-6H-1,3-oxazin-6-ones. The para substituent in the benzene ring does not affect the composition of the tautomer mixture significantly.For Communication 61, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 386–394, March, 1987.     

Synthesis and structure of styryl-substituted azines

New photochromic derivatives of 2-styrylquinoline and 2-styrylquinoxaline were obtained by the condensation of the methyl derivatives of the mentioned heterocycles with substituted benzaldehydes in the presence of basic and acidic catalysts, and also under the conditions of Wittig reaction. The structure of compounds obtained was proved by physicochemical analysis methods including XRD.     

Synthesis and certain properties of acetylenylindoles

A group of new acetylenic derivatives of indole was synthesized by condensation of 2- and 3-iodoindoles with terminal acetylenes. 3-Iodoindole unsubstituted at the heteroatom is distinguished by an increased tendency to undergo deiodination under the reaction conditions. Chemical transformations of the synthesized acetylenic derivatives were carried out, proceeding with both the retention of and with the participation of the triple bond. In the intramolecular cyclization of vicinal, functionally substituted indolylacetylenes, a tendency is manifested to form six-membered heterocycles. A primary pharmacological investigation of the compounds obtained was carried out. Most of them are slightly toxic, several of the compounds display in high doses indications of neurotropic activity.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 134–141, January, 1990.     

Some physicochemical properties of perfluoropolyether surfactants

Two series of surface active agents have been obtained, starting from intermediate products of HFP and TFE photooxidation :

Structural, physical and chemical properties have been summarized.Surface activity of the products in aqueous solution was examinated in terms of c.m.c. and H.L.B.Molecular cross section areas, derived from surface tension and Langmuir trough measurements, have been related to structural parameters.     

Oxidative reactions of azines

Oxidative coupling of 1-alkyl(benzyl)-4-(γ-pyridyl)-1,2,5,6-tetrahydropyridines with acetone in the presence of KMnO₄ follows two pathways and yields both 1-R-2-(acetylmethylene)tetrahydropyridines and 1-R-3,4-dihydroxypiperidin-2-ones. When acetonitrile is used instead of acetone, the reaction under similar conditions occurs as selective ketodihydroxylation of the starting piperideines yielding 1-R-3,4-dihydroxy-4-(γ-pyridyl)piperidin-2-ones. The molecular and crystal structures of one of these products (R=Et) was studied by X-ray diffraction analysis. For part 4, see Ref. 1 Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2020–2023, November, 1997.