Abstract
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 2O to produce three pentanuclear Mn(ii) clusters [Mn 5(PzCAP) 6](ClO 4) 4 (1), [Mn 5(PzOAP) 6](ClO 4) 4 (2) and [Mn 5(PyPzOAPz) 6] (ClO 4) 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 3O 3 chromophore and the equatorial centers have N 4O 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 2O in 1:1 mole proportion in CH 3OH:H 2O (60:40) forms a homoleptic [2 × 2] tetranuclear Cu 4(ii) grid [Cu 4(PzCAP) 4(NO 3) 2](NO 3) 2.8H 2O (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 2O in 1:1 mole proportion. This conversion of a cluster to a grid is a novel observation.
Original language | English |
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Pages (from-to) | 413-423 |
Number of pages | 11 |
Journal | Dalton Transactions |
Volume | 41 |
Issue number | 2 |
DOIs | |
State | Published - 14 Jan 2012 |