Non-linear optical properties of the mixed-metal mixed-chalcogen clusters [Fe-2(CO)(6){mu-SeC(Ph)=C(Se)}{(OEt)C =Cr(CO)(5)}] and [Fe-2(CO)(6)Se-2{mu-(CO)(3)Cr(eta(5)-C5H(CH2Ph)(Ph)(OEt)}]

We report studies of the third-order optical non-linearity of the newly syn thesized butterfly-shaped mixed-metal mixed-chalcogen clusters [Fe-2(CO)(6) {mu-SeC(Ph)=C(Se)}{(OEt)C=Cr(CO)(5)}] and [Fe-2(CO)(6)Se-2{mu-(CO)(3)Cr(eta (5)-C5H(CH2Ph)(Ph)(OEt)}] using 532 nm, 6 ns laser pulses. Their effective non-linear absorption coefficient and non-linear index intensity coefficien t are measured by the z-scan technique from which the corresponding cubic h yperpolarizabilities are evaluated. The obtained values indicate a high non -linearity comparable to some of the best values reported previously for cl uster compounds. Both compounds show strong optical limiting, and the secon d compound exhibits non-linear scattering. Their photostability is superior to many of the previously reported highly non-linear clusters. (C) 1999 El sevier Science B.V. All rights reserved.