RAMAN-SCATTERING PROPERTIES OF MO(V)=O AND MO(V)=S COMPLEXES AS PROBES FOR MOLYBDENUM-CONTAINING ENZYMES

The two monomeric Mo(V) complexes LMoOCl2 and LMoSCl2 having the ligand L = hydrotris(3,5-dimethyl-1-pyrazolyl)borate have been studied by Raman spectroscopy. Characteristic stretching frequencies for the {Mo = E}3+ unit (E = O, S) in the solid state are observed at 957 cm-1 for nu(Mo = O) and at 525 cm-1 for nu(Mo = S). Skeletal frequencies of the remaining {LMoCl2} moiety are not strongly affected by substitution of an oxo versus a sulfido ligand. Enhancement profiles obtained in backscattering from solid samples of the two chromophores show the LMoSCl2 compound to have a distinctive profile with maximum scattering at approximately 570 nm. However, the solution optical spectrum exhibits no absorption at this wavelength. The profile for the oxo analogue is rather constant in the visible range but suggests increased scattering intensity for nu(Mo = O) when approaching the UV region.