A Diuranyl(VI) Complex and Its Application in Electrocatalytic and Photocatalytic Hydrogen Evolution from Neutral Aqueous Medium.

The reaction of equimolar amounts of UO(OAc)·2HO, 2,6-diformyl-4-methylphenol, and -(hydroxyethyl)ethylenediamine in methanol affords a dinuclear -uranyl(VI) complex of the molecular formula [(UO)(μ-L)] (L = 2-formyl-4-methyl-6-((2-(2-oxidoethylamino)ethylimino)methyl)phenolate) in 65% yield. Detailed structural elucidation of the complex was performed by using single-crystal X-ray crystallographic and spectroscopic studies. In [(UO)(μ-L)], the metal centers are in edge-shared pentagonal-bipyramidal NO coordination spheres assembled by the two meridional ONNO-donor bridging L and two pairs of mutually trans oriented oxo groups. The complex is redox active and displays two successive metal-centered one-electron reductions at = -0.71 and -1.03 V in -dimethylformamide solution. The redox-active complex was used as a heterogeneous catalyst for electrochemical hydrogen evolution from aqueous medium at pH 7 with a turnover frequency (TOF) of 384 h and a Tafel slope of 274 mV dec. The Faradaic efficiency of [(UO)(μ-L)] was found to be 84%. Beyond the electrocatalytic response, the [(UO)(μ-L)]-TiO-N719 composite also exhibited significant heterogeneous photocatalytic hydrogen evolution activity in neutral aqueous medium under visible light and provided a yield of 3439 μmol g of H in 4 h with a TOF of 172 h and apparent quantum yield (AQY) of 7.6%.