Homoleptic and heteroleptic complexes of chromium(III) containing 4′-diphenylamino-2,2′:6′,2-terpyridine ligands

Two heteroleptic bis(2,2':6',2-terpyridine)chromium(III) complexes [Cr(1)(4'-(4-tolyl)tpy)][CF3SO3](3) and [Cr(2)(4'-(4-tolyl)tpy)][CF3SO3](3) (1 = 4-([2,2':6',2-terpyridin]-4'-yl)-N,N-diphenylaniline, 2 = 4-([2,2':6',2-terpyridin]-4'-yl)-N,N-bis(4-methoxyphenyl)aniline, 4'-(4-tolyl)tpy = 4'-(4-tolyl)-2,2':6',2-terpyridine) have been prepared and their spectroscopic and electrochemical properties compared with those of [Cr(4'-(4-tolyl)tpy)(2)][CF3SO3](3) and [Cr(1)(2)][CF3SO3](3). The single crystal structure of [Cr(4'-(4-tolyl)tpy)(2)] [CF3SO3](3)center dot 2MeCN is presented, and the effects of accommodating three triflate anions and two MeCN molecules per cation are discussed in terms of related structures. The coordination of 1 or 2 to chromium(III) red-shifts the intra-ligand charge transfer (ILCT) band and this band exhibits a negative solvatochromic effect in some solvents. However, in H2O, MeOH, DMSO and DMF, the tpy ligands are labile; changes in the absorption spectra of solutions of [Cr(2)(4'-(4-tolyl)tpy)][CF3SO3](3) are consistent with the formation of [Cr(4'-Xtpy)(Solv)(3)](3+) (Solv = solvent) rather than complete ligand displacement or a ligand redistribution. (C) 2015 Elsevier Ltd. All rights reserved.