The methoxo‐oxomolybdenum(V), diperoxomolybdenum(VI) and cis‐dioxomolybdenum(VI) derivatives of 5,15‐diphenyl‐2,8,12,18‐tetra‐n‐butyl‐3,7,13,17‐tetramethylporphyrin (4a, 5c, 6a) have been prepared and characterized by uv, ir, pmr, mass and esr spectra. The structure of the molybdenum(V) porphyrin was confirmed by X‐ray analysis.

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Using the combination of experimental (DFWM) measurements and electronic structure calculations, ligand electron donating power and explicit solvent interactions were shown to have critical roles in enhancing the χ3 yields for phosphonitrilic materials. Experimental measurements have shown that decreasing solution pH to 1.0 can significantly increase the χ3 yield for P3N3(NHCH3)6 and P3N3(N(CH3)2)6. Corresponding electronic structure calculations indicate replacement of amino by thiomethyl groups will also significantly enhance these yields. Comparison of electrostatic-based solvation effects and explicit water molecules indicates that dielectric stabilization from the solvent plays a minor influence on χ3 in comparison to strategies which affect the strong P-N bond polarity.

The optical response of polyphosphazenes can be directly related to the π (out-of-plane) and π′ (in-plane) bonding interactions intrinsic to the electronic structure of these Materials. Altering this structure either by hydrogen bonding or absórbate effects, affects both the linear and nonlinear optical susceptibilities. In this paper, we have performed electronic structure calculations on the cyclic Molecules, P3N3 (NHCH3)6, P3N3(SCH3)6, P3N3 (OCH3)6 and P4N4 (NHCH3)8 as model systems for the polymer. Charge distribution arguments are discussed to explain the influence of a polarizing electric field on the π bonding systems, and are used to suggest methods to enhance their nonlinearities.

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