Syntheses, molecular structures and optical nonlinearities of heteroselenometallic W–Se–Pd compounds containing bidentate phosphine ligands

Abstract

Reaction of [NEt₄]₂[WSe₄] with [Pd₂(dppm)₂Cl₂] afforded the hexanuclear windmill-shaped compound [(WSe₄)₂Pd₄(dppm)₂] (1) {dppm = bis(diphenylphosphino)methane}. Treatment of [NEt₄]₂[WSe₄] with [Pd(P^∧P)Cl₂] gave the dinuclear compounds [(WSe₄)Pd(P^∧P)] {P^∧P = dppe, 1,2-bis(diphenylphosphino)ethane (2); dppp, 1,3-bis(disphenylphosphino)propane (3)}. The crystal structures of these heteroselenometallic W–Se–Pd compounds have been determined and their nonlinear optical properties were studied with an 8 ns pulsed laser at 532 nm. It was found that compounds 1–3 show predominantly nonlinear refraction and negligible nonlinear absorption. Compound 1 exhibits a considerable self-defocusing properties with the nonlinear refractivity (n₂) value estimated to be −3.74 × 10⁻¹⁰ cm² W⁻¹ M⁻¹. The optical limiting thresholds of compounds 1, 2 and 3 were determined to be ca. 3.1, 6.5 and 7.2 J cm⁻², respectively.