The effects of axial ligands in Sn ( IV )-substituted 5,10,15,20-tetrakis [4-(carboethoxymethyleneoxy)phenyl]porphyrin and divalent transition metal substitution in 5,10,15,20-tetraphenylporphyrin on the second molecular hyperpolarizability (γ) at 802 nm were studied using the Z-scan technique. A significant increase in γ for divalent metal ions is observed with decreasing d-shell occupancy. In the case of the tetravalent metal-substituted porphyrin a dramatic enhancement of γ is seen when a strongly electronegative axial ligand such as I 2 is attached to the metal ion. A plausible explanation for the observed trend of γ has been sought in terms of metal-ligand interaction.

No abstract

No abstract

Dispersion of the second hyperpolarizability ␥(Ϫ;,,Ϫ) of a series of conjugated diacetylene derivatives measured by single beam Z-scan technique, is presented. The spectrum of ␥ is explained by a three-level model involving a one-photon excited state, a two-photon excited state and the ground state. The location of one and two-photon states and corresponding transition dipole moments have been estimated. The influence of various electronic states on the nonlinear optical properties of these derivatives have been discussed. Broad correlations of the nonlinearity with the structure have been drawn.

No abstract