Nonlinear Optical Materials from Cofacial Porphyrin Bridged Donor- Acceptor Molecules

摘要

A number of mutually-coordinated cofacial edge-over-edge metalloporphyrins have been sythesized and characterized by UV-visible, resonance Raman, time-resolved absorbance, nonlinear absorbance, fluorescence and NMR spectroscopic methods. Both homometallic and heterometallic dimers have been isolated. Excited state triplet absorbances of the dimeric complexes are red shifted, toward the second harmonic emission wavelength of Nd:YAG. In spite of the diminished singlet excited state lifetimes of these complexes relative to their monomeric counterparts, this shift results in significant nonlinear absorbance at 532 nm due to the increased triplet absorption cross section at that wavelength. Several dimers have been characterized by resonance Raman spectroscopy. The most interesting part of these spectra is in the low-frequency region where they contain bands not found in the spectra of the monomeric porphyrins. These bands have been analyzed in the context of intra-dimer vibrations.