Synthesis, characterisation and nonlinear optical properties of tetrahedral clusters Cp<SUB>2</SUB>Mo<SUB>2</SUB>ME(CO)<SUB>7</SUB>, (M=Fe, Ru, Os; E=S, Se)

A set of new chalcogen-bridged mixed metal clusters, Cp2Mo2M(&#956;3-E)(CO)7, (M=Fe, Ru, Os; E=S, Se) have been synthesised and characterised by IR and NMR spectroscopy, and structures of Cp2Mo2Ru(&#956;3-Se)(CO)7 and Cp2Mo2Os(&#956;3-Se)(CO)7 have been established by single crystal X-ray diffraction methods. The nonlinear optical properties of these clusters were investigated through the Z-scan technique, using 35 ps laser pulses at 532 nm. We report large refractive third order nonlinearity for these clusters indicating their promise for optical limiting applications