Mixed-valence trinuclear manganese(II/III) complexes of flexible tetradentate N2O2 ligands: Ferromagnetic versus antiferromagnetic coupling
作者:Qi-Wei Xie、Xi Chen、Kong-Qiu Hu、Yi-Tong Wang、Ai-Li Cui、Hui-Zhong Kou
DOI:10.1016/j.poly.2012.03.005
日期:2012.5
Four linear trinuclear manganese complexes containing ligands with an N2O2 donor set have been prepared and characterized structurally and magnetically. The complexes have the general formula [Mn-3(L-n)(2)(OAc)(2)(OCH3)(2)] (n = 1, 2, 3, 4. H2L1 = N,N'-dimethyl-N,N'-(2-hydroxy-4,5-dimethylbenzyl)ethylenediamine, H2L2 = N,N-bis(3,4-dimethyl-2-hydroxybenzyl)-N-(2-pyridylmethyl)amine, H2L3 = N,N-bis(3,4-dimethyl-2-hydroxybenzyl)-N,N'-dimethylethylenediamine, H2L4 = N,N-bis(3,4-dimethyl-2-hydroxybenzyl)-2-amino-ethanol). X-ray single-crystal structure analyzes of the complexes show that the linear Mn-III-Mn-II-Mn-III cores are triply bridged by phenolate. acetate (syn-syn), and MeO- groups with the Mn-III and Mn-II distances in the range 3.123(3)-3.167(4)angstrom. Magnetic studies show that the spin exchange coupling constants (J) between Mn-III and Mn-II ions range from -1.58(1) to 1.15(3) cm(-1) ((H) over cap = -2J((S) over cap (1) center dot (S) over cap (2) + (S) over cap (1) center dot (S) over cap (3))). The antiferromagnetic and ferromagnetic interactions were analyzed based on the structural features, and the Mn-III-O-Mn-II bond angles have been found to be the dominant factor affecting the intermetallic magnetic coupling. (C) 2012 Elsevier Ltd. All rights reserved.