METALLOPORPHYRINS FOR QUADRATIC NONLINEAR OPTICS

Cu-II- and Zn-II-based donor-acceptor porphyrins have been examined fo r second-order nonlinear optics using the hyper-Rayleigh scattering te chnique at 1064 nm. Introduction of the metal ions enhances the first hyperpolarizability (beta) of the free-base donor-acceptor porphyrins significantly. The open shell Cu-II (d(9)) has a greater influence on beta of these porphyrin systems than the closed shell Zn-II (d(10)). T he high beta values in the Zn-II porphyrins are understood in terms of the change in dipole moments upon excitation within the context of th e two-state model as well as two-photon resonance enhancement. In Cu-I I porphyrin complexes a large number of excited states seem to contrib ute to beta with, perhaps, a little contribution from two-photon reson ance at the excitation wavelength.