Three Asymmetrical Conjugated D-π-D′ Sulfur-Containing Chromophores with a Focus on Two-Photon Absorption

Three novel asymmetrical D-pi-D' type sulfur-containing chromophores, (E)-4-(4-(benzylthio)styryl)-N,N-diethylbenzenamine (S1), (E)-4-(4-(tert-butylthio)styryl)-N,N-diethylbenzenamine (S2) and (E)-4-(4-(thio)styryl)-N,N-diethylbenzenamine (S3), were synthesized and characterized. Two kinds of substituents and hydrogen were introduced into the three different chromophores to investigate the influence of electron distribution on the sulfur atom. Meanwhile, a simple synthetic strategy of pi-conjugated 4-(thio) styrene derivatives was performanced successfully. Linear and non-linear optical properties of S1, S2 and S3 were investigated both experimentally and theoretically. The optical properties indicate that they all have obvious characteristics of asymmetrical dipole molecules. The measured maximum two-photon cross-sections of S1-3 are 79, 57 and 19 GM (Goeppert-Mayer), respectively. It shows that the different substituents on the sulfur atom in molecules S1-3 lead to different electronic structures, which affect the optical properties. In these structures, the aromatic benzyl substituent (in S1) is superior for optimizing two-photon activity in the designed molecular framework.