Synthesis,Structure,Electronic Transfer And Proton Transfer Of Dimolybdenum Dimers Bridged By Asymmetric Ligands

Three dimolybdenum monomers Mo₂（DAniF）₃N2CC₆H₅, Mo₂（DAniF）₃NOCC₆H₅ and Mo₂（DAniF）₃O2CC₆H₅（DAniF = N,N￠-di（p-anisyl）formamidinate）, denoted as [NN?ph], [NO?ph] and [OO?ph], have been synthesized and characterized by 1H NMR. All of these compounds exibit a reversible one-electron redox process in cyclic voltammetry and their one-electron oxidation products present both MLCT and LMCT in Visible and near-infrared spectra, which prepared for the research behind.We report the study, in terms of electronic coupling and electron transfer（ET）, on three unsymmetrical Mo2 dimers [Mo₂（DAniF）₃]2[m-（NH）OCC6H4CO₂]（[NO-ph-OO]） [Mo₂（DAniF）₃]2[m-（NH）₂CC₆H₄CO₂]（[NN-ph-OO]） and [Mo₂（DAniF）₃]2[m-（NH）₂CC₆H₄C（NH）O]（[NN-ph-NO]）. The mixed-valence（MV） complexes [NO-ph-OO]+, [NN-ph-OO]+ and [NN-ph-NO]+ exhibit metal to ligand and ligand to metal charge transfer bands, along with an intervalence（IV） transition absorption in the Near-IR region. The free energy change（DG°） for ET is determined by comparing the redox potential splitting（DE1/2） and IV transition energy（EIT） with the data for the symmetrical species. The reorganization energy（l） is estimated from Hush model. Significantly, electrochemical and optical analyses verify EIT = DG° + l, the core energetic relationship underling the semi-classical theories. With the electronic coupling parameters calculated from CNS model, the forward adiabatic ET rate constants ket（f） are smaller than ket（r） for the backward reaction and ket for the symmetrical analogues by one order of magnitude. This work illustrates that the redox asymmetry in D-B-A systems controls the ET rate and direction.In addition, this text synthesized a dimolybdenum monomer Mo₂（DAniF）₃O2CC₆H₅CNO,abbreviated as [Mo2O2?ph?NO], which could form dimolybdenum dimmers that bridged by hydrogen bonding in nonpolar solvent. The study indicates that there is no IVCT transition but proton transfer in this hydrogen bonding compound.