Synthesis and properties of highly-rigid conjugation system based on bi(benzo[b]thiophene)-fused o-carborane

To demonstrate the validity of o-carborane as an electronic anchoring unit for constructing robust conjugation system, bi(benzo[b]thiophene)-fused o-carborane was designed and synthesized. From the optical measurements, clear vibrational bands not only in the absorption but also in the emission spectra were observed. These data mean that the electronic delocalization should occur on the rigid template. In the cyclic voltammograms, the reversible reduction waves at 1.72 eV and 2.37 eV were detected that originated from the electron-accepting ability of o-carborane. It is suggested that o-carborane should be the versatile unit for constructing robust conjugation with electron-accepting ability. (C) 2016 Elsevier Ltd. All rights reserved.