title: An orthogonal ferromagnetically coupled tetracopper(II) 2 x 2 homoleptic grid supported by micro-O4 bridges and its DFT study.
abstract: 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(NO3)2] (NO3)2.4H2O (1) with a central Cu4[micro-O4] core, involving four ligand molecules. In the Cu4[micro-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 degrees) and Cu-Cu distances are short (4.043-4.131 A), 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 (d(x2-y2)) lying almost orthogonally between the metal centers. The exchange pathways parameters have been evaluated from density functional calculations.
authors.affiliation: Department of Chemistry, University College of Science, 92, A.P.C. Road, Kolkata, 700 009, India.
authors.forename: Somnath
authors.initials: S
authors.lastname: Roy
authors.forename: Tarak Nath
authors.initials: TN
authors.lastname: Mandal
authors.forename: Anil Kumar
authors.initials: AK
authors.lastname: Barik
authors.forename: Sachindranath
authors.initials: S
authors.lastname: Pal
authors.forename: Ray J
authors.initials: RJ
authors.lastname: Butcher
authors.forename: Mohamed Salah
authors.initials: MS
authors.lastname: El Fallah
authors.forename: Javier
authors.initials: J
authors.lastname: Tercero
authors.forename: Susanta Kumar
authors.initials: SK
authors.lastname: Kar