Synthesis, spectroelectrochemical characterization and solvatochromic studies of arylazoimidazolepalladium(II) catecholates

Abstract

The ternary complexes, [Pd(RaaiCH2Ph)(OO)](4–6), where RaaiCH2Ph = N(1)-benzyl-2-(arylazo)imidazole [p-RC6H4N=NC3H2N2CH2Ph (2), R = H (4), Me (5) and Cl (6)] and (OO) = catechol [catH2,(a)], 4-t-butylcatechol [tbcatH2, (b)], 3,5-di-t-butylcatechol [dtbcatH2, (c)] and tetrachlorocatechol [tccatH2, (d)], have been prepared and characterized by elemental analyses, i.r., u.v.-vis. and 1H-n.m.r. data. Cyclic voltammograms suggest four successive redox responses that are highly sensitive to the nature of the substituents. The complexes exhibit a ligand-to-ligand charge transfer (LLCT) band and a negative solvatochromic effect. The position of the band is largely dependent on the substituent type on the catechol frame and is qualitatively assigned as the 3b1(cat) → π*(aai) transition.