An orthogonal ferromagnetically coupled tetracopper(ii) 2 × 2 homoleptic grid supported by µ-O₄bridges 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.

Use of Acylhydrazine‐ and Acylhydrazone‐Type Ligands to Promote CuI‐Catalyzed C–N Cross‐Coupling Reactions of Aryl Bromides with N‐Heterocycles

“…The ligands that formed two chelating rings with copper(I), such as L3, L8-10, were less efficient than L2, which formed one chelating ring with copper(I); this can probably be ascribed to the strong coordinating ability of the former to copper(I), because the catalytically active species involves the simultaneous coordination of both nitrogen and oxygen atoms to the copper(I) atom. [8,23] To determine the most suitable reaction conditions for the N-arylation of imidazole, the catalytic system was examined by using different copper sources, bases, solvents, and catalyst loading; the results are listed in Table 1. It was found that the copper source is important for effective catalysis; CuI was the most reactive, and the respective combination of CuBr, CuSO 4 ·5H 2 O, and Cu with either L2 or Scheme 1.…”

“…The transformation between hindered and functionalized azoles and aryl halides was achieved in good to excellent yields. It is known that acylhydrazine and acylhydrazone derivatives possess high affinity and selectivity to metal ions, [21][22][23] and some insight into their binding and chelating ability to copper has also been explored. [22,23] A broad variety of substituents could also be introduced to the backbone units, which gives an opportunity to flexibly adjust their properties and coordinating ability to metal ions by varying the substituents.…”

“…It is known that acylhydrazine and acylhydrazone derivatives possess high affinity and selectivity to metal ions, [21][22][23] and some insight into their binding and chelating ability to copper has also been explored. [22,23] A broad variety of substituents could also be introduced to the backbone units, which gives an opportunity to flexibly adjust their properties and coordinating ability to metal ions by varying the substituents. Although acylhydrazine-and acylhydrazonetype ligands have been extensively used in coordination chemistry, [21][22][23] they are seldom chosen as ligands in catalysis.…”

“…[22,23] A broad variety of substituents could also be introduced to the backbone units, which gives an opportunity to flexibly adjust their properties and coordinating ability to metal ions by varying the substituents. Although acylhydrazine-and acylhydrazonetype ligands have been extensively used in coordination chemistry, [21][22][23] they are seldom chosen as ligands in catalysis. The success of N,O-ligands in Cu-catalyzed C-N formation reactions prompted us to examine whether these types of ligands could be useful for the N-arylation of azoles with aryl halides, especially with inexpensive aryl and heteroaryl bromides.…”

Tetranuclear Copper(II) Complexes Bearing Cu4O6 and Cu4O4 Cores: Synthesis, Structure, Magnetic Properties, and DFT Study

“…[12][13][14][15][16][17][18][19][20] Thus, here we also present a full brokensymmetry density functional theory (BSDFT) investigation to obtain better insight into the exchange coupling of these systems. for 1 and 2, respectively.…”