The Impact of Ligand Oxidation State and Fold Angle on the Charge Transfer Processes of MoO-Dithione Complexes.

We report a series of mononuclear monooxo Mo(IV) complexes possessing either one or two fully oxidized dithiolene ligands; [MoOCl(RDt)][X], ( and ), and MoO(-SCHY)(RDt), ( and ), (R=Me, Pr; X= PF, SbF, BF; Y= H, Cl, F, CF, Me, Bu, OMe). Either four or two quasi-reversible ligand-based redox couples are detected depending upon the number of fully oxidized dithiolene ligands present. The molecular structure of and exhibit a large (47° to 70°) fold angle along the S•••S vector of the dithione ligand. The UV-Vis spectra of and exhibit a low energy charge transfer band at ~540 nm that are red-shifted ~200 nm compared to the spectra of and . Density Functional Theory (DFT) calculations show that the low energy charge transfer band of and is heavily influenced by ligand fold angle. Reducing the fold angle decreases the charge transfer energy, and the transition becomes more ligand-based.