3RD-ORDER NONLINEAR-OPTICAL PROPERTIES OF DONOR-SUBSTITUTED AND ACCEPTOR-SUBSTITUTED METALLOPHTHALOCYANINES

Several types of metallophthalocyanines have been synthesized to estab lish the relationship between molecular structure and third-order opti cal non-linearity. Third-order non-linear optical susceptibilities chi ((3)) of phthalocyanine (Pc) containing central metal atoms oxovanadiu m, copper, nickel, iron and cobalt, and peripheral substitutes were me asured by the third-harmonic generation technique. The chi((3))(-3 ome ga; omega, omega, omega) values of VOPc(NH2)(4), CuPc(NH2)(4), NiPc(NH 2)(4) and FePc(COOH)(4) were found to be 6.3 x 10(-12), 2.0 x 10(-2), 1.63 x 10(-12) and 1.18 x 10-(12) e.s.u. respectively at 2.1 mu m. Alt hough the donor and acceptor substituents have a dilution effect, chi( (3)) was still larger than that of the corresponding unsubstituted pht halocyanines, with the exception of metallophthalocyanines with an axi al group where the peripheral substituents required for processability or otherwise are not beneficial for optical non-linearity. In additio n, the magnitude of chi((3))(-3 omega; omega, omega, omega) was found to be influenced by different functional groups substituted in cobalt phthalocyanine. The effect of various peripheral substituents on the m agnitude of the third-order non-linear optical susceptibility is discu ssed.