Department of Chemistry, University College of Science, University of Calcutta, 92, APC Road, Kolkata 700 009, India.
Inorg Chem. 2012 May 7;51(9):5332-41. doi: 10.1021/ic300274n. Epub 2012 Apr 11.
Two new Mn(III) complexes of formulas MnL(1)(N(3))(OMe) (1) and MnL(2)(N(3))(2) (2) have been synthesized by using two tridentate NNO-donor Schiff base ligands HL(1){(2-[(3-methylaminoethylimino)-methyl]-phenol)} and HL(2) {(2-[1-(2-dimethylaminoethylimino)methyl]phenol)}, respectively. Substitution of the H atom on the secondary amine group of the N-methyldiamine fragment of the Schiff base by a methyl group leads to a drastic structural change from a methoxido-bridged dimer (1) to a single μ(1,3)-azido-bridged 1D helical polymer (2). Both complexes were characterized by single-crystal X-ray structural analyses and variable-temperature magnetic susceptibility measurements. The magnetic properties of compound 1 show the presence of weak ferromagnetic exchange interactions mediated by double methoxido bridges (J = 0.95 cm(-1)). Compound 2 shows the existence of a weak antiferromangetic coupling along the chain (J = -8.5 cm(-1)) through the single μ(1,3)-N(3) bridge with a spin canting that leads to a long-range antiferromagnetic order at T(c) ≈ 9.3 K and a canting leading to a weak ferromagnetic long-range order at T(c) ≈ 8.5 K. It also exibits metamagnetic behavior at low temperatures with a critical field of ca.1.2 T due to the weak antiferromagnetic interchain interactions that appear in the canted ordered phase.
已合成了两个新的 Mn(III) 配合物，化学式为 MnL(1)(N(3))(OMe)（1）和 MnL(2)(N(3))(2)（2），分别使用两种三齿 NNO-供体希夫碱配体 HL(1){(2-[(3-甲基氨基乙基亚氨基)-甲基]-苯酚)}和 HL(2) {(2-[1-(2-二甲基氨基乙基亚氨基)甲基]苯酚)}。希夫碱的 N-甲基金二胺片段上的仲胺氢原子被甲基取代，导致结构发生剧烈变化，由甲氧基桥联二聚体（1）变为单 μ(1,3)-叠氮桥联 1D 螺旋聚合物（2）。两个配合物均通过单晶 X 射线结构分析和变温磁化率测量进行了表征。化合物 1 的磁性研究表明，双甲氧基桥（J = 0.95 cm(-1)）存在微弱的铁磁交换相互作用。化合物 2 表现出沿链的弱反铁磁耦合（J = -8.5 cm(-1)），通过单 μ(1,3)-N(3)桥连接，存在自旋倾斜，导致在 T(c) ≈ 9.3 K 时出现长程反铁磁有序，在 T(c) ≈ 8.5 K 时出现自旋倾斜导致弱铁磁长程有序。由于在倾斜有序相中存在弱反铁磁链间相互作用，它还在低温下表现出反铁磁行为，临界场约为 1.2 T。
