Synthesis and characterization of new fluorescent two-photon absorption chromophores

A series of dipolar and quadrupolar type two-photon absorption (TPA) compounds has been synthesized and TPA cross sections (sigma) were measured by Ti:sapphire femtosecond laser excitation fluorescence (lambda = 800 nm). Among them, the compound [2,5-bis-[5-(4diphenylaminophenylethynyl)thiophen-2-yl]-[1,3,4]oxadiazole], 12, has been structurally characterized by X-ray crystallography. The resulting data indicate that the structure of this compound possesses excellent coplanarity. The compounds have arylamines as the donor, and [1,3,4]oxadiazolyl, cyanovinyl or pyridazin-3,6-diyl moiety as the acceptor. Variation of arylamines and pendant alkyl groups was found to have a significant influence on sigma values. By an appropriate combination of donor and acceptor, sigma values of > 10(3) GM (10(-50) cm(4)s photon(.)molecule(-1)) can be achieved. One quadrupolar molecule (13) possessing an arylamine donor and a pyridazine acceptor has both a high sigma value (1442 GM) and sigma/MW (1.97 GM/g).