THE MIXED-METAL CLUSTER (N-BU(4)N)(2)[MOCU3OS3(NCS)(3)] - THE FIRST EXAMPLE OF A NEST-SHAPED COMPOUND WITH LARGE 3RD-ORDER POLARIZABILITY AND OPTICAL LIMITING EFFECT

A mixed metal nido-cluster, (n-Bu(4)N)(2)[MoCu3OS3(NCS)(3)], was discovered to exhibit large third-order polarizability (gamma) and optical limiting effect. This is the first example of a nest-shaped compound with large nonlinear optical coefficients. The magnitude of the third-order polarizability, \gamma\=4.8x10(-29) esu, was determined with 7-ns laser pulses of 532 nm wavelength by a degenerate four-wave mixing technique. An irradiance-dependent transmission measurement was conducted to assess the contribution of nonlinear absorption to the gamma value. These results, in combination with those of a Z-scan experiment, yielded a negative value for the real part of gamma, Re gamma=-4.8x10(-29) esu. The negative sign of Re gamma reveals that the nido-cluster has an interesting optical self-defocusing property. The optical limiting effect of the cluster was also demonstrated.