One-Photon Photophysics and Two-Photon Absorption of 4-[9,9-Di(2-ethylhexyl)-7-diphenylaminofluoren-2-yl]-2,2′:6′,2"-terpyridine and Their Platinum Chloride Complexes

The synthesis, one-photon photophysics and two-photon absorption (2PA) of three dipolar D-pi-A 4-[9,9-di(2-ethylhexyl)-7-diphenylaminofluoren-2-yl]-2,2':6',2 ''-terpyridine and their platinum chloride complexes with different linkers between the donor and acceptor are reported. All ligands exhibit (1)pi,pi* transition in the UV and (1)pi,pi*/(1)ICT (intramolecular charge transfer) transition in the visible regions, while the complexes display a lower-energy (1)pi,pi*/(1)CT (charge trans-fer) transition in the visible region in addition to the high-energy (1)pi,pi* transitions. All ligands and the complexes are emissive at room temperature and 77 K, with the emitting excited state assigned as the mixed (1)pi,pi* and (1)CT states at RT. Transient absorption from the ligands and the complexes were ob-served. 2PA was investigated for all ligands and complexes. The two-photon absorption cross-sections (sigma(2)) of the complexes (600-2000 GM) measured by Z-scan experiment are much larger than those of their corresponding ligands measured by the two-photon induced fluorescence method. The ligand and the complex with the ethynylene linker show much stronger 2PA than those with the vinylene linker.