Temperature-dependence of spectral and photophysical properties of polycyclic aromatic hydrocarbon derivatives of acetylene and buta-1,3-diyne

Abstract Variable-temperature absorption and emission data over the range 80–300 K have been collected for acetylene and buta-1,3-diyne derivatives with polycyclic aromatic hydrocarbons as substituents, in 2-methyltetrahydrofuran (2-MeTHF). The influence of temperature on fluorescence lifetime and quantum yield has also been investigated. A strong coupling between solvation dynamics and solute structure is observed. Moreover, the dependency of fluorescence quantum yield on temperature indicates that the energy of activation of conformational changes for studied compounds is comparable or slightly larger than the activation energy of viscous flow of 2-MeTHF. Moreover, contrary to diphenyl derivatives of buta-1,3-diyne for which conformation changes are barrierless, polycyclic aromatic hydrocarbons derivatives are characterized by a relatively high activation energy.