Synthesis, characterization, and optoelectronic study of three biaryl-fused closo-o-carboranes and their nido-[C2B9]- species

A biaryl-fused closo-o-carborane with a phenylthiophene moiety was synthesized and reacted with fluoride to obtain its nido-[C2B9](-) species; the reaction with fluoride to obtain nido-[C2B9](-) species was also performed for biphenyl- and bithiophene-fused o-carboranes, the synthesis of which we have previously reported. The structures and optoelectronic properties of the three carboranes and their nido-[C2B9](-) species were experimentally and theoretically characterized. The nido-[C2B9](-) species possessed high HOMO and LUMO energy levels because of the electron-rich anion species. They also displayed charge transfer (CT) transition bands, and efficient CT emissions were observed in the crystalline as well as solution state because of the shorter carbon carbon bond length in the nido-carborane cage and suppression of the carbon-carbon bond vibration. (C) 2015 Elsevier B.V. All rights reserved.