Accurate UV–visible spectral analysis of thiomolybdates

The UV–visible spectra of various thiomolybdates have been studied. Cross-contamination during synthesis and extensive overlap in the spectra have hindered the UV–vis characterization to date. We report the use of multivariate curve fitting for the accurate quantification of the composition of thiomolybdate mixtures as well as the molar absorptivities at key wavelengths of the spectrum of each pure thiomolybdate. The synthesis and isolation of all four thiomolybdates by a common synthetic route using (NH4)2S is also reported. This is the first time that monothiomolybdate has been isolated from aqueous solution.Key words: Thiomolybdates, UV–visible spectroscopy, speciation, curve fitting.