A radical-bridged bis(ferrocenylcopper(I)) complex: Structural identity, multifrequency EPR, and spectroelectrochemistry

Abstract The paramagnetic blue complex {(μ-adcO t Bu)[Cu(dppf)] 2 }(PF 6 ) contains two heterodinuclear 1,1′-bis(diphenylphosphinoferrocene)copper(I) moieties, bridged by the radical anion of di- tert -butylazodicarboxylic ester (adcO t Bu). The assignment of oxidation states is supported by crystal structure determination and by variable frequency EPR spectroscopy which provides hyperfine (9.5 GHz) and g anisotropy information (285 GHz). Cyclic voltammetry and UV/Vis/NIR spectroelectrochemistry indicate reversible one-electron oxidation of the adcO t Bu − bridge prior to the quasi-reversible two-electron oxidation of the well separated (12.55 A) ferrocene termini. One-electron reduction to the adcO t Bu 2− bridged system occurs with concomitant loss of the long-wavelength metal-to-ligand charge transfer absorption.