Octahedral molybdenum cluster complexes with aromatic sulfonate ligands

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 (nBu(4)N)(2)[{Mo6X8}(OTs)(6)] and (nBu(4)N)(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 (nBu(4)N)(2)[{Mo6X8}(OTs)(6)] and (nBu(4)N)(2)[{Mo6X8}(PhSO3)(6)] confer enhanced stability towards electrochemical oxidation relative to corresponding starting complexes (nBu(4)N)(2)[{Mo6X8}X-6].