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■ Systematic Investigation of Fluorescence Properties of Symmetric and Asymmetric Diazolo[1,2-a:2′,1′-c]quinoxaline Derivatives

Shoji Matsumoto,* Keisuke Sakamoto, and Motohiro Akazome

*Department of Applied Chemistry and Biotechnology, Graduate School and Faculty of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan

Abstract

The investigation of the synthesis and optical properties of symmetric and asymmetric diazolo[1,2-a:2′,1′-c]quinoxaline derivatives were systematically examined. The formation of an intramolecular carbon-carbon bond between two azole rings could be achieved by selection of the reaction depending on the type of azole. The absorption and fluorescence spectra revealed the following effects induced by structural changes: 1) introduction of a fused-benzene ring affects the peak shape and the increment of 0-0 transition in the absorption and fluorescence spectra. 2) A hypsochromic shift is induced by substitution of the CH moiety with a nitrogen atom. 3) Introduction of fused-benzene ring(s) is a promising strategy for improving the fluorescence quantum yield of these species. Furthermore, all of the compounds were fluorescent in the solid state, although no systematic trend was found. Investigation of the single crystal structures revealed a diversity of crystal packing arrangements, even in related structures.