Third-order susceptibilities of asymmetric pentaazadentate porphyrin-like metal complexes

The third-order nonlinear optical properties of a series of asymmetric pentaazadentate porphyrin-like metal complexes ([(R-APPC)M]Cl_n) with different conjugated R groups and metal centers have been investigated by degenerate four wave mixing experiments using 40 ps laser pulses at 532 nm. The molecular second-order hyperpolarizabilities (γ) for these complexes range from 1.1X10^-31 to 1.2X10^-30 esu and depend strongly on both the nature of the metal and the R group. The y values of the [(R-APPC)Cd]Cl complexes are 2-7 times larger than those of PbPc(CP)₄ and SiNc, two of the most promising nonlinear optical materials for optical limiting applications. Measurements of the individual components of the χ⁽³⁾ tensor indicate that the nonlinearity is predominantly electronic in origin when 40 ps laser pulses are used.