Bandgap Engineering of Titanium–Oxo Clusters: Labile Surface Sites Used for Ligand Substitution and Metal Incorporation

Through the labile coordination sites of a robust phosphonate‐stabilized titanium–oxo cluster, 14 O‐donor ligands have been successfully introduced without changing the cluster core. The increasing electron‐withdrawing effect of the organic species allows the gradual reduction of the bandgaps of the {Ti₆} complexes. Transition‐metal ions are then incorporated by the use of bifunctional O/N‐donor ligands, organizing these {Ti₆} clusters into polymeric structures. The coordination environments of the applied metal ions show significant influence on their visible‐light adsorption. Both the above structural functionalizations also tune the photocatalytic H₂ production activities of these clusters. This work provides a systematic bandgap engineering study of titanium–oxo clusters, which is important not only for their future photocatalytic applications, also for the better understanding of the structure–property relationships.