Ligand Influence on the Photophysical Properties and Electronic Structures of Tungsten Iodide Clusters

Compounds containing the [Mo6I8L6]2– ion in which L is an inorganic or organic ligand show remarkable photophysical properties. Similar properties were observed for the corresponding compounds based on octahedral tungsten clusters. The properties of these photosensitizers are significantly impacted by the six outer iodide ligands of [W6I8I6]2–. To analyze the role of the outer ligands, we prepared and structurally characterized octahedral tungsten cluster compounds with [W6I8I6]2– and [M6I8L6]2– ions (M = W, Mo; L = para‐toluenesulfonate). The distinct photophysical properties of the clusters were analyzed with respect to their photoluminescence (i.e., phosphorescence) and luminescence quenching in the presence of molecular oxygen. The electronic structures were analyzed through photoelectron spectroscopy to expose differences in the electronic situations of the compounds. Significant differences in the phosphorescence‐quenching behavior owing to molecular O2 and the electronic structures are shown by the all‐iodide cluster [W6I14]2– in comparison to those of the ligand‐substituted [W6I8L6]2– and [Mo6I8L6]2– clusters (exemplified by L = toluenesulfonate).