The effect of pressure has been measured on the absorption spectra of (nhyphen;Bu4N)2Re2X8(X=Cl, Br, I), K4Mo2Cl8, (NH4)4Mo2Br8, and Re2lsqb;CCO2(CH3)3rsqb;2X8(Xrsquo;=Cl, Br). For the rhenium and molybdenum halides in the solid state a distinct shift to lower energy (red shift) was observed for the dgr;rarr;dgr;ast; excitation. In solution the shift of the dgr;rarr;dgr;ast; was red in CH2Cl2but exhibited a complex behavior in the associated solvents CH3CN and CH3NO2which we attributed to solvation of the ion. The dipivalate molecules in CH3CN exhibited a red shift as one might expect as they are less solvated. The pgr;rarr;pgr;ast; excitations in the rhenium bromide and iodide showed a blue shift which increased with pressure. We discuss the observed shifts in terms of the relative importance ofintraandintermolecular interactions.
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