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Issue 44, 2011
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Self assembled tetranuclear Cu4(II), Ni4(II) [2 × 2] square grids and a dicopper(II) complex of heterocycle based polytopic ligands - Magnetic studies

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Abstract

The ditopic ligand PyPzOAP (N-[(Z)-amino(pyridin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid) and the polytopic ligand 2-PzCAP (N3,N5-bis[(1E)-1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3,5-dicarbohydrazide) were synthesized in situ by condensation of methyl imino picolinate with 5-methyl-1-(2-pyridyl) pyrazole-3-carbohydrazide and 2-acetyl pyridine with pyrazole-3,5-dicarbohydrazide respectively. The ligands PyPzOAP and PzOAP (reported earlier, Dalton Trans., 2007, 1229) self-assemble to form homoleptic [2 × 2] tetranuclear M4 (M = Cu(II) and Ni(II)) square grids structures [Cu4(PyPzOAP)4](NO3)4 (1), [Cu4(PzOAP)4](ClO4)4 (2) and [Ni4(PyPzOAP)4](NO3)4·8H2O·2CH3CN (3). While the ligand 2-PzCAP forms a dicopper(II) complex [Cu2(2-PzCAP)(OH)(NO3)(H2O)](NO3)·2H2O (4). The complex 1 is a perfect square grid (a = 4.201 Å), whereas, 2 and 3 are almost square grids. All these compounds have been characterized by X-ray structural analyses and variable temperature magnetic susceptibility measurements. EPR studies have also been carried out for complexes 1, 2 and 4. In the Cu4 grid (1), all the Cu(II) centers are in a distorted octahedral environment with N4O2 chromophore, while, in complex 2, all four Cu(II) centers have a square pyramidal environment with N3O2 chromophore. In complex 3, all four Ni(II) centers have distorted octahedral geometry with N4O2 chromophore. In compound 4, the Cu(II) centers are in square pyramidal environment with N3O2 chromophore. The magnetic properties of compounds 1 and 2 show the presence of intramolecular ferromagnetic exchange interaction (J = 5.88 cm−1 for 1 and 4.78 cm−1 for 2). The complex 3 shows weak intramolecular antiferromagnetic interaction (J = −4.02 cm−1). While, complex 4, shows strong antiferromagnetic behavior (J = −443 cm−1).

Graphical abstract: Self assembled tetranuclear Cu4(ii), Ni4(ii) [2 × 2] square grids and a dicopper(ii) complex of heterocycle based polytopic ligands - Magnetic studies

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Publication details

The article was received on 02 May 2011, accepted on 23 Aug 2011 and first published on 05 Oct 2011


Article type: Paper
DOI: 10.1039/C1DT10813A
Citation: Dalton Trans., 2011,40, 11866-11875
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    Self assembled tetranuclear Cu4(II), Ni4(II) [2 × 2] square grids and a dicopper(II) complex of heterocycle based polytopic ligands - Magnetic studies

    T. N. Mandal, S. Roy, S. Konar, A. Jana, S. Ray, K. Das, R. Saha, M. S. El Fallah, R. J. Butcher, S. Chatterjee and S. K. Kar, Dalton Trans., 2011, 40, 11866
    DOI: 10.1039/C1DT10813A

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