Dimeric Mn(ii), Co(ii), Ni(ii) and Cu(ii) complexes of a common carboxylate-appended (2-pyridyl)alkylamine ligand: structure, magnetism and DFT study

Abstract

Four new complexes of composition [MII2(L3)2(CH3OH)2](ClO4)2(M = Mn,1; Co,2; Ni,3) and [CuII2(L3)2](ClO4)2(4) (L3(−) = 3-[2-(((6-methyl)pyridin-2-yl)methyl){(dimethylamino)ethyl}-amino]propionate) have been synthesized and characterized. Structural analysis reveals that1-4are discretesyn-anticarboxylate-bridged binuclear coordination complexes with a {MII2(-O-C-O-)2}2+structural motif. In1-3distorted octahedral MN3O3and in4distorted square pyramidal CuN3O2coordination is satisfied at each M(ii) center by three N (a pyridyl and two tertiary aliphatic amines) and a carboxylate O of the ligand, and an O of the carboxylate group. In1-3the M(ii) center is also coordinated by a CH3OH molecule. Variable-temperature magnetic measurements reveal the presence of weak antiferromagnetic interactions in1and weak ferromagnetic interactions in2-4. The electronic structure of1-4has been probed by density functional theory (DFT) calculations at the B3LYP level of theory. In order to gain insight into the origin of the observed electronic transitions, time-dependent (TD)-DFT calculations have been done.