Platinum(II) Diimine Complexes with Catecholate Ligands Bearing Imide Electron-Acceptor Groups : Synthesis, Crystal Structures, (Spectro)Electrochemical and EPR studies, and Electronic Structure

A series of catechols with attached imide functionality (imide = phthalimide PHT, 1,8-naphthalimide NAP, 1,4,5,8-naphthalenediimide NDI, and NAP-NDI) has been synthesized and coordinated to the PtII(bpy*) moiety, yielding Pt(bpy*)(cat-imide) complexes (bpy* = 4,4′-di-tert-butyl-2,2′-bipyridine). X-ray crystal structures of PHT and NAP complexes show a distorted square-planar arrangement of ligands around the Pt center. Both complexes form “head-to-tail” dimers in the solid state through remarkably short unsupported Pt···Pt contacts of 3.208 (PHT) and 3.378 A (NAP). The Pt(bpy*)(cat-imide) complexes are shown to combine optical (absorption) and electrochemical properties of the catecholate (electron-donor) and imide (electron-acceptor) groups. The complexes show a series of reversible reduction processes in the range from −0.5 to −1.9 V vs Fc+/Fc, which are centered on either bpy* or imide groups, and a reversible oxidation process at +0.07 to +0.14 V, which is centered on the catecholate moiety. A combina...