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

Tarak Nath Mandal, Somnath Roy, Saugata Konar, Atanu Jana, Sangita Ray, Kinsuk Das, Rajat Saha, Mohamed Salah El Fallah, Ray J. Butcher, Sudipta Chatterjee, Susanta Kumar Kar

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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 (N′3, N′5-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).

Original languageEnglish
Pages (from-to)11866-11875
Number of pages10
JournalJournal of the Chemical Society. Dalton Transactions
Volume40
Issue number44
DOIs
StatePublished - 9 Nov 2011

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