Functionalized oligothiophene-based heterocyclic aromatic fluorescent compounds with various donor–acceptor spacers and adjustable electronic properties: a theoretical and experimental perspective

Syntheses, characterizations, optical, electrochemical, and thermal properties of a family of linear oligothiophene-based heterocyclic aromatic fluorescent compounds are described herein. They all have effective π-conjugated systems with D–π–D or A–π–A structures as well as different bromo, thiocyano, formyl, and triphenylamino tails. X-ray single-crystal structure of 2TPA2T methanol semisolvate reveals a trans configuration with different dihedral angles between adjacent aromatic heterocycles. Theoretical and experimental studies have been made to reveal the differences from related compounds with adjustable electronic properties. The influences of introducing different D/A functionalized tails on the band-gap convergence have also been discussed, where the convergence behavior corrected via the thienyl ring coefficient (ncorr) shows better correlation of linear fitting based on the extrapolation of HOMO−LUMO gaps at the B3LYP/6-31G∗ level.