Alteration of nonlinear refraction by mixing clusters [WOS3Cu3I(py)5] and [MoOS3Cu3I(Py)5]

Abstract

A new cluster compound [WOS3Cu3I(Py)5] (I) was synthesized by substitution reactions of (Et4N)3[WOS3-Cu3I4] with pyridine and structurally determined by X-ray diffraction. It crystallizes in monoclinic, space group C2/c (No. 15), a - 24.341(1), b = 10.020(4), c = 26.64(1) Å, V = 6424(3) Å3, and Z = 8. The cluster has a nest-shaped skeleton. The nonlinear optical properties of both I and [MoOS3Cu3I(py)5] (II) in acetonitrile solutions were measured using a Z-scan technique with 7-ns and 532-nm laser pulses. Compound I possesses a self-focusing property (n2 = 1.6 × 10-9 cm2 W-1 M-1), while compound II exhibits a self-defocusing property (n2 = -1.3 × 10-10 cm2 W-1 M~'). Both compounds show reverse saturable absorption (α2 = 1.5 × 10-4 and 2.5 × 10-5 cm W-1 M-1 for compounds I and II, respectively). We demonstrate that the nonlinear refraction of a mixture containing the two compounds can be altered from self-focusing, through a state where self-lensing disappears, to self-defocusing by varying the ratio of the two compounds.