Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata, 700 009, India.
Dalton Trans. 2012 Jan 14;41(2):413-23. doi: 10.1039/c1dt11458a. Epub 2011 Oct 21.
The ditopic ligand PyPzOAPz (N-[(Z)-amino(pyrazin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid) was synthesized by in situ condensation of methyl imino pyrazine-2-carboxylate with 5-methyl-1-(2-pyridyl) pyrazole-3-carbohydrazide. In this work we have also used two of our earlier ligands PzCAP (5-methyl-N-[(1E)-1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazonic acid) (Dalton Trans., 2009, 8215) and PzOAP (N-[(Z)-amino(pyridin-2-yl)methylidene]-5-methyl-1H-pyrazole-3-carbohydrazonic acid) (Dalton Trans., 2007, 1229). These ligands PzCAP, PzOAP and PyPzOAPz were made to react with Mn(ClO(4))(2)·6H(2)O to produce three pentanuclear Mn(II) clusters Mn(5)(PzCAP)(6)(4) (1), Mn(5)(PzOAP)(6)(4) (2) and Mn(5)(PyPzOAPz)(6)(4) (3). These complexes have been characterized by X-ray structural analyses and variable temperature magnetic susceptibility measurements. All complexes have a pentanuclear core with trigonal bipyramidal arrangement of Mn(II) atoms, where, the axial metal centers have a N(3)O(3) chromophore and the equatorial centers have N(4)O(2) with an octahedral arrangement. These Mn(5)(II) clusters 1, 2 and 3 show the presence of antiferromagnetic coupling within the pentanuclear manganese(II) core (J = -2.95, -3.19 and -3.00 cm(-1) respectively). Density functional theory calculations and continuous shape measurement (CShM) studies have been performed on these complexes to provide a qualitative theoretical interpretation of the antiferromagnetic behaviour shown by them. The pentanuclear Mn(II) cluster (1) on reaction with Cu(NO(3))(2)·6H(2)O in 1:1 mole proportion in CH(3)OH:H(2)O (60 : 40) forms a homoleptic [2 × 2] tetranuclear Cu(4)(II) grid Cu(4)(PzCAP)(4)(NO(3))(2)(2)·8H(2)O (4). The same Cu(4)(II) grid is also obtained from a direct reaction between the ditopic ligand PzCAP with Cu(NO(3))(2)·6H(2)O in 1:1 mole proportion. This conversion of a cluster to a grid is a novel observation.
双齿配体 PyPzOAPz（N-[(Z)-氨基（吡嗪-2-基）亚甲基]-5-甲基-1-（吡啶-2-基）-1H-吡唑-3-甲脒酸）是通过将甲基亚氨基吡嗪-2-羧酸与 5-甲基-1-（2-吡啶基）吡唑-3-甲脒酸原位缩合合成的。在这项工作中，我们还使用了我们之前的两种配体 PzCAP（5-甲基-N-[(1E)-1-（吡啶-2-基）乙基亚甲基]-1H-吡唑-3-甲脒酸）（Dalton Trans.，2009，8215）和 PzOAP（N-[(Z)-氨基（吡啶-2-基）亚甲基]-5-甲基-1H-吡唑-3-甲脒酸）（Dalton Trans.，2007，1229）。这些配体 PzCAP、PzOAP 和 PyPzOAPz 与 Mn（ClO4）2·6H2O 反应生成三个五核 Mn（II）簇[Mn（5）（PzCAP）（6）]（ClO4）4（1），[Mn（5）（PzOAP）（6）]（ClO4）4（2）和[Mn（5）（PyPzOAPz）（6）]（ClO4）4（3）。这些配合物通过 X 射线结构分析和变温磁化率测量进行了表征。所有配合物都具有五核核心，其中 Mn（II）原子呈三角双锥排列，轴向金属中心具有 N（3）O（3）发色团，而赤道中心具有 N（4）O（2），呈八面体排列。这些 Mn（5）（II）簇 1、2 和 3 显示出五核锰（II）核内存在反铁磁耦合（分别为 J =-2.95、-3.19 和-3.00 cm-1）。对这些配合物进行了密度泛函理论计算和连续形状测量（CShM）研究，为它们表现出的反铁磁行为提供了定性的理论解释。五核 Mn（II）簇 1 在与 Cu（NO3）2·6H2O 以 1:1 摩尔比例在 CH3OH:H2O（60:40）中反应时，形成了同核[2×2]四核 Cu（4）（II）网格[Cu（4）（PzCAP）（4）（NO3）2]（NO3）2·8H2O（4）。同样的 Cu（4）（II）网格也可以通过配体 PzCAP 与 Cu（NO3）2·6H2O 以 1:1 摩尔比例直接反应得到。这种从簇到网格的转化是一个新的发现。
