Large hyperpolarizabilities of trinuclear transition metal clusters [MAg2X4(C5H5NS)(PPh3)2]·CH2Cl2 (M = Mo, W; X = S, Se): a DFT study

Abstract

Static and dynamic first hyperpolarizabilities have been studied by a DFT approach for a series of trinuclear heterometallic transition metal molecular clusters, [MAg₂X₄(C₅H₅NS)(PPh₃)₂]·CH₂Cl₂ (M = Mo, W; X = S, Se) with incomplete cubane-like configurations. Their nonlinear optical nature has been analyzed by using a two-level model. The large hyperpolarizabilities of about 100 × 10⁻³⁰ esu of these metal clusters are generated by intermolecular charge transfers from the metal core to the pyridine-2-thiol ligand as well as by intramolecular charge transfers within the metal core. The conjoint effects of stereo π (3D) conjugation of the metal core and planar π (2D) conjugation of the C₅H₅NS ligand enhance these hyperpolarizabilities, while the presence of CH₂Cl₂ has a negative effect by lowering them. Since these complexes are all crystallized in noncentrosymmetric configurations, they are promising candidates as IR second-order nonlinear optical transition metal coordinated materials.