Theoretical and experimental studies of phenol oxidation by ruthenium complex with N,N,N-tris(benzimidazol-2yl-methyl)amine

Abstract

The ruthenium complex with (N,N,N-tris(benzimidazol-2yl-methyl)amine, L(1)) was prepared, and characterized. Fukui data were used to localize the reactive sites on the ligand. The structural and electronic properties of the complex were analyzed by DFT in different oxidation states in order to evaluate its oxidant properties for phenol oxidation. The results show that the hard Ru(IV) cation bonds preferentially with a hard base (Namine = amine nitrogen, or axial chloride ion), and soft Ru(II) with a soft base (Nbzim = benzimidazole nitrogen or axial triphenyl phosphine). Furthermore, the Jahn-Teller effect causes an elongation of the axial bond in the octahedral structure. The bonding nature and the orbital contribution to the electronic transitions of the complex were studied. The experimental UV-visible bands were interpreted by using TD-DFT studies. The complex oxidizes phenol to benzoquinone in the presence of H2O2 and the intermediate was detected by HPLC and (13)C NMR. A possible mechanism and rate law are proposed for the oxidation. The adduct formation of phenol with [Ru(O)L(1)](2+) or [Ru(OH)L(1)](+) is theoretically analyzed to show that [Ru(OH)L(1)-OPh](+) could produce the phenol radical.

Bio‐inspired Photocatalytic Ruthenium Complexes: Synthesis, Optical Properties, and Solvatochromic Effect

“…The short 60 ns component might be attributed to a non‐radiative relaxation, in agreement with the lower emission quantum yield of the new complexes. A non‐radiative relaxation process can take place by two sequential electron transfers, first from the phenol group to the Ru 3+ center, and subsequently from the bipyridine group to the transient phenoxyl radical, such that the molecule retains its ground state . The significance of this process is the formation of a stable phenoxyl radical, which can participate in water splitting …”

Electrochemical oxidation of sulfamethazine on a glassy carbon electrode modified with graphene and gold nanoparticles

“…The evaluation of molecular reactivity was accomplished by Condensed-to-Atoms Fukui Indexes (CAFIs) [26]. In general, such parameters carry information regarding local tendencies to insert electrons into or withdraw them from molecules, enabling identification of the sites that are most susceptible to undergoing electrophilic, nucleophilic or radical reactions [27].…”

“…In the work described here, the CAFIs were obtained in a DFT/B3LYP/PCM/6-31G(p,d). Hirshfeld's population analysis was employed to avoid non-realistic negative CAFIs [26].…”