Chiral Diuranyl(VI) Complexes and Their Catecholase Activities: Experimental and Theoretical Insights

Abstract

Two enantiomeric pairs of complexes, [(UO 2 ) 2 (R/S-L 1 ) 2 (H 2 O) 2 ] ⋅ 2MeCN and [and their characterization by elemental analysis, mass spectrometry, various spectroscopy and X-ray crystallography are reported. In each complex, trans-UO 2 2 + units are in edge-shared NO 4 pentagonal planes formed by the two alkoxide end bridging ONO-donor (R/S-L 1/2 ) 2À and the two solvent molecules. The first pair is inactive, while the second pair is active towards catecholase activity. The mass spectra suggest formation of the adduct {complexÀ Me 2 NCHO + substrate} and EPR spectra indicate a radical pathway for the catalytic reaction. Computational studies indicate that primarily the binding strength of the solvent molecule dictates the adduct formation and hence the catalytic inactivity/activity. Based on experimental observations and theoretical calculations a four step mechanism has been proposed for the catalytic activities of the second pair of complexes.