The homoleptic [2 x 2] tetranuclear compound [Cu-4(PyPzCAF)(4)](NO3)(4)center dot 8H(2)O (1) and the pentanuclear Mn(II) cluster [Mn-5(PyPzCAP)(6)](ClO4)(4)center dot 4C(6)N(6) (2) are self-assembled from the ditopic pro-ligand HPyPzCAP [(5-methyl-1-(pyridin-2-yl)-N'-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide)]. Complex 1 is almost a square grid, and all the Cu(II) centers show a distorted octahedral environment with an N4O2 chromophore. Complex 2 has a pentanuclear core with a trigonal bipyramidal arrangement of the Mn(II) atoms. The axial Mn centers bear an N3O3 chromophore and the equatorial centers have an N4O2 distorted octahedral arrangement. Complex 1 shows a ferromagnetic exchange interaction (J = +4.62 cm(-1) and g = 2.05), whereas 2 shows weak an antiferromagnetic interaction (J = -2.73 cm(-1) and g = 2.02). Both complexes 1 and 2 catalyze the allylic oxidation of cyclohexene to cyclohex-2-ene-1-one with good selectivity and an excellent overall turnover number. (c) 2013 Elsevier Ltd. All rights reserved.

ATANU JANA

SAUGATA KONAR

KINSUK DAS

SANGITA RAY

JAMES A GOLEN

ARNOLD L RHEINGOLD

FALLAH MOHAMED SALAH EL

SANGHAMITRA MUKHERJEE

SAMIK GUPTA

ARMANDO J L POMBEIRO

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Polyhedron

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. © 2012 The Royal Society of Chemistry.

Dalton Transactions

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

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). © 2011 The Royal Society of Chemistry.

Fulltext

Self assembled tetranuclear Cu<inf>4</inf>(ii), Ni<inf>4</inf>(ii) [2 Ã— 2] square grids and a dicopper(ii) complex of heterocycle based polytopic ligands - Magnetic studies

The synthesis and structure of a pyrazole-based orthogonal ferromagnetically coupled tetracopper(II) 2 × 2 homoleptic grid complex [Cu4(PzOAPyz)4(ClO4)2](ClO4)2 · 6H2O (1), formed by the reaction between the ditopic ligand PzOAPyz and Cu(ClO4)2 · 6H2O, are described. The ligand contains terminal pyrazole and pyrazine residues bound to a central flexible diazine subunit (N-N) as well as one potentially bridging alkoxo group. The two adjacent metal centers are linked by an alkoxo oxygen forming essentially a square Cu4(μ-O4) cluster. In the Cu4(μ-O4) core, out of the four copper centers, two copper centers are penta-coordinated and the remaining two are hexa-coordinated. In each case of hexa-coordination, the sixth position is occupied by one of the oxygen atoms of a coordinated perchlorate ion. Complex 1 has been characterized structurally and magnetically. Although the large Cu-O-Cu bridge angles (137-138°) and short Cu-Cu distances (3.964-3.970 Å) are suitable for the transmission of the expected antiferromagnetic coupling, the square-based Cu4(μ-O4) cluster exhibits an intramolecular ferromagnetic exchange (J = 7.47 cm-1) between the metal centers with an S = 2 magnetic ground state associated with the quasi orthogonal arrangement of the magnetic orbitals (dx2 - y2). The exchange pathway parameters have been evaluated from density functional calculations. © 2007 Elsevier Ltd. All rights reserved.

A pyrazole-based orthogonal ferromagnetically coupled [2 Ã— 2] homoleptic square Cu4 grid: Magnetostructural correlations

A pyrazole based ditopic ligand (PzOAP), prepared by the reaction between 5-methylpyrazole-3-carbohydrazide and methyl ester of imino picolinic acid, reacts with Cu(NO3)2·6H2O to form a self-assembled, ferromagnetically coupled, alkoxide bridged tetranuclear homoleptic Cu(ii) square grid-complex [Cu4(PzOAP)4(NO 3)2] (NO3)2·4H2O (1) with a central Cu4[-O4] core, involving four ligand molecules. In the Cu4[-O4] core, out of four copper centers, two copper centers are penta-coordinated and the remaining two are hexa-coordinated. In each case of hexa-coordination, the sixth position is occupied by the nitrate ion. The complex 1 has been characterized structurally and magnetically. Although Cu-O-Cu bridge angles are too large (138-141°) and Cu-Cu distances are short (4.043-4.131 Å), suitable for propagation of expected antiferromagnetic exchange interactions within the grid, yet intramolecular ferromagnetic exchange (J = 5.38 cm-1) is present with S = 4/2 magnetic ground state. This ferromagnetic interaction is quite obvious from the bridging connections (dx2-y2) lying almost orthogonally between the metal centers. The exchange pathways parameters have been evaluated from density functional calculations. © The Royal Society of Chemistry 2007.

An orthogonal ferromagnetically coupled tetracopper(II) 2 Ã— 2 homoleptic grid supported by -O4 bridges and its DFT study

Chemical Communications

Ionic liquids with metal chelate anions

A [2 x 2] Cu-4 molecular grid and a Mn-5 cluster derived from a 1-(2-pyridyl)pyrazole based polytopic ligand - Synthesis, structure, magnetic properties and catalytic activity in the allylic oxidation of cyclohexene

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