Synthesis, characterization, and nonlinear optical study of metalloporphyrins

Meso-Tetrakis{4-[2-(trimethylsilyl)ethynyl]phenyl}porphyrin [TPP(4-CCTMS)_H2] and its complexes with Zn-II, Ni-II, Ga-III, In-III, and Sn-IV were synthesized and characterized. Their nonlinear optical transmission characteristics were determined using a 532 nm, 5 ns pulsed laser at a repetition rate of 20 Hz. Stronger nonlinear absorption was obtained with the zinc derivative, Zn-II-meso-tetrakis{4-[2-(trimethylsilyl)ethynyl]phenyl}porphyrin (TPP(4-CCTMS)_Zn), than with the standard analogues, Zn-II-meso-tetraphenylporphyrin (TPP_Zn), and Zn-II-meso-tetratolyl-porphyrin (TPP_Zn), indicating that the excited-state absorption can be influenced via fine molecular modification on the para-position of the meso-phenyl rings, without changing the ground-state absorption. The nonlinear optical response can be further enhanced via insertion of closed-shell metal ions. In particular, (InCl)-Cl-III-meso-tetrakis{4-[2-(trimethylsilyl)ethynyl]phenyl}porphyrin (TPP(4-CCIMS)_InCl), exhibited a larger change in transmission with increasing energy than C-60 and a comparable change to the state-of-the-art phthalocyanine dye, chloro(tetra(tert-butyl)phthalocyanato)indium(III) (Pc(t-Bu)_InCl).