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The optical properties of ter-thiophene, diphenyl-thiophene, dithieno-thiophene and their analogues with the central sulphur atom functionalized with two oxygen atoms are investigated by first-principles time-dependent density-functional theory: absorption and emission energies and singlet–triplet energy-gaps are reported and compared with experimental results. Photoluminescence quantum yield measurements in solvents of different viscosity for the functionalized systems are reported. The non-radiative decay channels are discussed. [Copyright &y& Elsevier]

The effects of intermolecular interactions on the photoluminescence (PL) quantum efficiency of differently substituted thienylene-S,S-dioxide derivatives in the crystalline phase are investigated. The exciton resonance interactions and the transfer integrals are evaluated using a quantum chemistry approach by considering the supramolecular structures obtained from X-ray data. Two classes of thienylene-S,S-dioxides are investigated: (1) rigid, fused ring compounds, for which the PL quantum efficiency can be well correlated with the rate of formation of non-radiatively decaying charge-transfer pairs upon photoexcitation; (2) flexible oligothiophenes for which the high PL quantum efficiency in the solid-state is assigned to a decrease of intramolecular internal conversion process, as confirmed by time-resolved PL measurements in solvents of different viscosity. [Copyright &y& Elsevier]