Spectral Luminescent Properties of 2-Aryl-5-(2,6-dimethoxyphenyl)-1H-1,3,4-oxadiazoles

Abstract

Abstract-2-Aryl-5-(2,6-dimethoxyphenyl)-1H-1,3,4-oxadiazoles were synthesized by cyclization reaction of benzoylbenzohydrazides in SOCl 2 , and their spectral luminescent properties were studied. The oxadiazoles containing phenyl or o-methoxyphenyl substituents in the position 2 were shown to luminesce with a high quantum yield in polar and nonpolar solvents. The replacement of these substituents by 2-hydroxyphenyl group led to oxadiazole intensely emitting only in highly polar aprotic DMSO.Keywords: 2,5-diaryl-1,3,4-oxadiazoles, luminescence, luminescence quantum yield, organic phosphors ISSN 1070-3632, Russian Journal of General Chemistry, 2018, Vol. 88, No. 2, pp. 338-341. © Pleiades Publishing, Ltd., 2018. Original Russian Text © I.E. Mikhailov, Yu.M. Artyushkina, G.A. Dushenko, O.I. Mikhailova, Yu.V. Revinskii, V.I. Minkin, 2018, published in Zhurnal Obshchei Khimii, 2018 1,3,4-Oxadiazoles and their derivatives belong to one of the most intensively studied classes of fivemembered nitrogen-containing heterocycles characterized by good synthetic accessibility and high structural variability, as well as by wide range of practical applicability. These compounds have diverse biological activity [1] and are extensively used in various fields of medicinal chemistry [2] and pesticide chemistry [3]. Also, they possess interesting spectral luminescent properties making them suitable for the preparation of widely demanded organic [4][5][6][7] and metal complex-based [8,9] phosphors. LETTERS TO THE EDITORFor expanding the range of compounds of this class and for studying their spectral luminescent properties we applied here the reaction of hydrazides 1a-1c with 2,6-dimethoxybenzoic acid chloride in the presence of triethylamine to obtain benzoylbenzohydrazides 2a-2c whose subsequent cyclization with thionyl chloride led to 2-aryl-5-(2,6-dimethoxyphenyl)-1H-1,3,4-oxadiazoles 3a-3c (Scheme 1).In the absorption spectra of oxadiazoles 3a-3c the maximum of the long-wave band due to π→π* electron transitions is observed within the 256-316 nm range, consistent with their benzenoid structure. The luminescence spectra of oxadiazole 3b in isooctane, toluene, and acetonitrile contain two bands: a shortwave band (λ m fl ax 353-378 nm, φ 0.001-0.012) which has a normal Stokes shift (3019-4992 cm

Synthesis, photophysical and nonlinear optical properties of push–pull tetrazoles

“…8 Similarly, the widely employed electron acceptors exhibit negative mesomeric or inductive effect (–M/–I) that comprise of –NO 2 , –CN, –CHO, –COOH groups as well as heterocycles such as pyridine, imidazoles, benzothiazoles, benzooxazoles and many others. 8 Push-pull chromophores containing the heterocyclic cores – oxazoles, 15–19 oxadiazoles 20–23 and triazoles 24,25 have received much attention in recent years, however, studies on the photophysical and NLO properties of the related tetrazole-based molecular systems are scarce in the literature. For instance, photophysical properties of compounds containing a tetrazole scaffold have been reported.…”