Deprotonation in Mixed-Valent Diiron(II,III) Complexes with Aniline or Benzimidazole Ligands

Protonation-Induced Reversible Switching of Electronic Delocalization in a Linear Ru-Ru-Ru Complex

In this work, we report the first example of a molecular switch between electronic delocalization and electronic localization in cyanidometal-bridged trinuclear mixed-valence (MV) complex controlled by a protonation reaction. A MV complex with the terminal 2,3-bis(diphenylphosphino)pyridine (L) ligand which has a higher proton-accepting character, LRuIII-NC-RuII-CN-RuIIL (13+) was synthesized and well characterized. The investigations indicate that the interaction between the two terminal Ru centers of 13+ is so strong that it is fully delocalized and can be described as LRuII+0.5-NC-RuII-CN-RuII+0.5L. Most interestingly, 13+ can be reversibly protonated to 13+-2H coupled with an electron transfer from the central RuII to the terminal RuIII, resulting in a change in electronic structure from LRuII+0.5-NC-RuII-CN-RuII+0.5L to HLRuII-NC-RuIII-CN-RuIILH. Cyclic voltammogram of 13+-2H showed very weak interaction between the two terminal Ru centers. The remarkable change in electronic states by protonation-induced electron transfer is also strongly supported by the (TD)DFT calculations. Complex 13+ may be potential for an excellent candidate of molecular switch.

Mixed Valence (μ-Phenoxido) FeII FeIII et FeIII FeIV Compounds: Electron and Proton Transfers

Mixed-valence non-heme diiron centers are present at the active sites of a few enzymes and confer them interesting reactivities with the two ions acting in concert. Related (μ-phenoxido)diiron complexes have been developed as enzyme mimics. They exhibit very rich spectroscopic properties enabling independent monitoring of each individual ion, which proved useful for mechanistic studies of catalytic hydrolysis and oxidation reactions. In our studies of such complexes, we observed that these compounds give rise to a wide variety of electron transfers (intervalence charge transfer), proton transfers (tautomerism), coupled electron and proton transfers (H^. abstraction and PCET). In this minireview, we present and analyze the main results illustrating the latter aspects.

The synthesis of three new Cu5, Cu8 and Cu12 clusters via the use of a semi-flexible aminotriazine-based bis-methylpyridine ligand

The use of a semi-flexible aminotriazine-based bis-methylpyridine ligand afforded three new Cu₅, Cu₈ and Cu₁₂ complexes.