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Issue 2, 2012
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Synthesis, structural, magnetic, DFT calculations and CShM studies of three new pentanuclear Mn(II) clusters

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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(ClO4)2·6H2O to produce three pentanuclear Mn(II) clusters [Mn5(PzCAP)6](ClO4)4 (1), [Mn5(PzOAP)6](ClO4)4 (2) and [Mn5(PyPzOAPz)6](ClO4)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 N3O3 chromophore and the equatorial centers have N4O2 with an octahedral arrangement. These Mn5(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(NO3)2·6H2O in 1 : 1 mole proportion in CH3OH:H2O (60 : 40) forms a homoleptic [2 × 2] tetranuclear Cu4(II) grid [Cu4(PzCAP)4(NO3)2](NO3)2·8H2O (4). The same Cu4(II) grid is also obtained from a direct reaction between the ditopic ligand PzCAP with Cu(NO3)2·6H2O in 1 : 1 mole proportion. This conversion of a cluster to a grid is a novel observation.

Graphical abstract: Synthesis, structural, magnetic, DFT calculations and CShM studies of three new pentanuclear Mn(ii) clusters

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Publication details

The article was received on 02 Aug 2011, accepted on 08 Sep 2011 and first published on 21 Oct 2011


Article type: Paper
DOI: 10.1039/C1DT11458A
Citation: Dalton Trans., 2012,41, 413-423
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    Synthesis, structural, magnetic, DFT calculations and CShM studies of three new pentanuclear Mn(II) clusters

    T. N. Mandal, S. Roy, S. Konar, A. Jana, K. Das, S. Ray, S. Gupta, R. Saha, M. S. El Fallah, J. Tercero, R. J. Butcher, S. Chatterjee and S. K. Kar, Dalton Trans., 2012, 41, 413
    DOI: 10.1039/C1DT11458A

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