Swivel-cruciform stilbenes based on bithiophene

Abstract

Bithiophene-based cruciforms with different stilbenoid arms at the 3,3′- and 5,5′-positions have been synthesized by various combinations of Suzuki and Horner–Wadsworth–Emmons (HWE) reactions. According to DFT calculations, the steric hindrance between the arms at the 3,3′-positions produces a twist angle of 57.6° between the two thiophene rings that form the 2,2′-bithiophene unit, an arrangement that leads to a swivel-cruciform structure. The UV/Vis spectra contained strong absorption bands at wavelengths consistent with a twisted molecule with little interaction between the arms. The ability of these compounds to form highly stable radical cations was demonstrated by cyclic voltammetry and this, together with their good solubility in organic solvents, indicates that these materials have potential for the development of solution-processed electronic devices.This research was funded by the Spanish Ministerio de Economía y Competitividad (MINECO) and the European Union (EU) (FEDER project BFU2011-30161-C02-02). The Junta de Comunidades de Castilla-La Mancha (JCCM) is thanked for financial support (FEDER project PEII-2014-005-A) and a doctoral fellowship to A. G.-R.Peer reviewe