Cross-exchange of donor units in donor-acceptor-donor type conjugated molecules: Effect of symmetrical and unsymmetrical linkage on the electrochemical and optical properties

A series of donor-acceptor-donor type molecules were synthesized using carbazole (C) and thiophene (T) as donor units. The donors were connected symmetrically and unsymmetrically to the acceptor unit of benzothiadiazole (B). With having four combinations, CBC, CBT, TBT and CTBTC, changes in the electrochemical and optical behaviors of the monomers were investigated using cyclic voltammetry, differential pulse voltammetry, UV–Vis and Fluorescence spectrometry techniques. Replacing one of the symmetrical C units in CBC with T unit caused a slight red shift in lower energy absorption band. On the other hand, having both C and T units symmetrically in the monomer structure exhibited about 70 nm red shift in the optical absorption. Electrochemical polymerization of the monomers was studied via potential cycling. In the case of formation of polymer films, the effect of exchange and combination of the donors on the electrochemical and optical properties was investigated. [Display omitted] •Cross-Exchange of Donor Units in Donor-Acceptor-Donor Type Conjugated Molecules.•Effect of symmetrical and unsymmetrical linkage of donor units.•Electrochemical and optical properties changed with changing donors.•High Stoke’s shift was observed for all monomers.