Phenanthroline−Polyoxometalate Hybrid Compounds and the Observation of Intramolecular Charge Transfer

Abstract

A phenanthroline ligand has been covalently modified at the 2 and 9 positions by an aminophenylhexamolybdate substituent. The 1H NMR spectrum indicated a strong electron-withdrawing effect of the hexamolybdate (Mo6O19(2-)) moiety on the phenanthroline ligand. UV-vis and cyclic voltammetry showed extended conjugation of the hybrid phenanthroline-polyoxometalate compound and the possibility of easy oxidation of the extended phenanathroline ligand. Further EPR experiments provided strong evidence for an intramolecular charge-transfer process with the formation of a phenanthroline cation radical and a reduced hexamolybdate.

Unprecedented Replacement of Bridging Oxygen Atoms in Polyoxometalates with Organic Imido Ligands

“…[14][15][16][17][18] In principle, the bridging oxygen atoms in POMs can also be replaced by organoimido ligands; however, such a bridging organoimido-substituted POM has not been obtained to date. This result is surprising, as bridging organoimido ligands have been found in oligonuclear or polynuclear early-transitional-metal complexes, [19][20][21] and the isoelectronic alkoxo groups in the bridging mode have been widely observed in polyoxoalkoxometalates.…”

Investigation of the catalytic behavior of a Cu coordination polymer capped polyoxometalate as an oxidation catalyst

“…Based on our knowledge comparing this work with those reported before, the activity and stability of the prepared catalyst is considerable, because of the strong effect observed upon attachment of polyoxometalate, leading to an intramolecular charge separation and description of (1) as a charge-transfer compound. [4,31,32,33]. The novelty of this work is high selectivity and heterogeneous character of compound 1 as catalyst.…”

Liquid-Phase Selective Oxidation by Multimetallic Active Sites of Polyoxometalate-Based Molecular Catalysts

“…Although the lacunary POMs can activate H 2 O 2 to form peroxo species at vacant sites [47], the oxidation catalysis by lacunary POMs has scarcely been reported [73,[98][99][100] 4À and the epoxidation mechanism have been reported [104][105][106][107][108][109]. The inorganic-organic hybrid POMs have attracted much attention because the electron and steric properties of the POMs significantly affect the catalytic properties of the metal centers [110][111][112]. A hybrid catalyst consisted of a metallosalen complex attached covalently to a lacunary POM [SiW 11 O 39 ] 8À via two propyl spacers.…”