Charge-transfer transitions in triarylamine mixed-valence systems: the effect of temperature

The temperature dependence of inter-valence charger-transfer transitions has been investigated for three triarylamine-based mixed-valence systems: (bis-{4-[N,N-di(4-methoxyphenyl)amino]-phenyl}butadiyne, 1+), (4,4′-bis[N,N-di(4-methoxyphenyl)amino] biphenyl, 2+), and (N,N,N′,N′-tetraphenyl-1,4-phenylenediamine, 3+). Although the band shape of 1+–3+ changes with temperature, neither the position of the transition maximum nor the integral intensity are significantly affected by temperature. The shape of the absorption bands is analyzed in the framework of a dynamic vibronic model.