Synthesis, crystal structure and large third-order nonlinear optical properties of two novel nest-shaped clusters [MOS3Cu3(SCN)(Py)5] (M = Mo, W)

Two new candidates for nonlinear optical (NLO) materials, [MoOS3Cu3(SCN)(Py)(5)] (1) and [WOS3Cu3(SCN)(Py)(5)] (2), were synthesized. They show nest-shaped skeletal structure. The crystal structure of compound (1) was characterized by X-ray diffraction. The NLO properties of 1 and 2 were determined through the Z-scan technique. [MoOS3Cu3(SCN)(Py)(5)] exhibits both very strong NLO absorption and a self-defocusing effect, alpha(2) = 4.8 x 10(-10) m W-1 and n(2) = -6.8 x 10(-17) W-1 in a 2.0 x 10(-5) mol dm(-3) acetonitrile solution. NLO properties of compound [WOS3Cu3(SCN)(Py)(5)] are similar to those of [MoOS3Cu3(SCN)(Py)(5)], strong NLO absorption and self-defocusing effect, alpha(2) = 6 x 10(-11) m W-1 and n(2) = -1.2 x 10(-17) W-1, when measured in a 1.9 x 10(-5) mol dm(-3) DMF solution. Their hyperpolarizability gamma values were calculated to be 5.8 x 10(-27) esu for cluster 1 and 2.2 x 10(-27) esu for cluster 2, respectively. The large gamma value should define clusters 1 and 2 as very promising candidates for NLO materials.