Octahedral molybdenum cluster complexes with aromatic sulfonate ligands

Abstract

This article describes the synthesis, structures and systematic study of the spectroscopic and redox properties of a series of octahedral molybdenum metal cluster complexes with aromatic sulfonate ligands (ⁿBu₄N)₂[{Mo₆X₈}(OTs)₆] and (ⁿBu₄N)₂[{Mo₆X₈}(PhSO₃)₆] (where X⁻ is Cl⁻, Br⁻ or I⁻; OTs⁻ is p-toluenesulfonate and PhSO₃⁻ is benzenesulfonate). All the complexes demonstrated photoluminescence in the red region and an ability to generate singlet oxygen. Notably, the highest quantum yields (>0.6) and narrowest emission bands were found for complexes with a {Mo₆I₈}⁴⁺ cluster core. Moreover, cyclic voltammetric studies revealed that (ⁿBu₄N)₂[{Mo₆X₈}(OTs)₆] and (ⁿBu₄N)₂[{Mo₆X₈}(PhSO₃)₆] confer enhanced stability towards electrochemical oxidation relative to corresponding starting complexes (ⁿBu₄N)₂[{Mo₆X₈}X₆].