Synthesis, Electronic, Magnetic and Structural Characterization of New Trinuclear Mixed‐Valence Co ^III ‐Co ^II ‐Co ^III Complex.

Abstract

Abstract The structural, electronic, magnetic and theoretical study of the complex [Co 3 (HL) 2 ( μ ‐AcO) 2 (AcO) 2 ], 1 , (HL is the dianion obtained by deprotonation of N,N’‐bis(salicylidene)‐2‐hydroxy‐1,3‐propanediamine and AcO is acetate) shows that 1 crystallizes with two independent molecules in the asymmetric unit. Each molecule is a trinuclear complex. Both molecules have similar geometry, and correspond to a spin system based on trapped mixed valences on six‐coordinate metal centres, Co III ( s =0)‐Co II ( s =3/2)‐Co III ( s =0). The rigid framework formed by the tetradentate Salen‐type ligands HL and the syn‐syn bridging acetate anions is a characteristic feature observed in other related complexes. However, the here reported compound is the first one in this family having Z’>1. UV‐Vis spectrum shows a broad band in the visible region where d‐d transition for ions Co III and Co II are. EPR spectra and the electronic energy estimations of the ground state show the presence of two conformers s=3/2. The χ M T product at 300 K is 3.24 emu mol −1 K per trinuclear unit, this product is expected for Co II where the contribution of orbital angular moment is taken into account (3.38 emu mol −1 K for L =3).