Two new oxalato-bridged dinuclear copper(II) complexes with di-2-pyridylamine: crystal structures, spectroscopic and magnetic properties

μ2-Oxalato-bridged tricopper(II) complex derived from 1,4,8,12-tetraazacyclopentadecane: Synthesis, structure and magnetic characterization

“…Many oxalato-nickel(II) and -copper(II) compounds have been isolated, and magnetically and structurally characterized [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In most cases, dinuclear metal(II) complexes were obtained where the oxalate ligand is binding the two metals in bis-bidentate bridging mode [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In the dinuclear oxalato-bridged Cu(II) complexes where the separation distance between the two Cu(II) ions is in the range of 5-6 Å , moderate to strong antiferromagnetic interactions were observed with the singlet-triplet energy gap, J value is as large as À386 cm À1 in [Cu 2 (tmen) 2 (H 2 O) 2 (C 2 O 4 )](ClO 4 ) 2 Á 1.25H 2 O (tmen = N, N,N 0 ,N 0 -tetramethylethylenediamine) [7][8][9][10][11][12][13][14][15]20].…”

“…In most cases, dinuclear metal(II) complexes were obtained where the oxalate ligand is binding the two metals in bis-bidentate bridging mode [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In the dinuclear oxalato-bridged Cu(II) complexes where the separation distance between the two Cu(II) ions is in the range of 5-6 Å , moderate to strong antiferromagnetic interactions were observed with the singlet-triplet energy gap, J value is as large as À386 cm À1 in [Cu 2 (tmen) 2 (H 2 O) 2 (C 2 O 4 )](ClO 4 ) 2 Á 1.25H 2 O (tmen = N, N,N 0 ,N 0 -tetramethylethylenediamine) [7][8][9][10][11][12][13][14][15]20]. The great plasticity of the coordination sphere of the Cu(II) center (four, five and six coordination sphere) which allows the variation of the orientation and symmetry of the molecular orbital describing its unpaired electron (magnetic orbital) is believed to be a crucial parameter for the presence of such enormous number complexes.…”

“…Many oxalato-nickel(II) and -copper(II) compounds have been isolated, and magnetically and structurally characterized [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In most cases, dinuclear metal(II) complexes were obtained where the oxalate ligand is binding the two metals in bis-bidentate bridging mode [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

Structural and Magnetic Properties of Monomeric and Dimeric Copper(II) Complexes with Phenyl-N-[(pyridine-2-yl)methylene]methaneamide

“…This observation is caused from the equilibrium between the mononuclear and binuclear complexes in the solution. 5,20 The solution and powder EPR spectrum of Cu(ppmma)Br 2 at 77 K exhibited an isotropic broad singlet with the value of <g> ~ 2.0. Hatfield and co-workers 21 have shown that the singlettriplet exchange coupling J varies in a regular way with the quotient θ/R, where θ is the Cu-Cl-Cu' bridging angle and R is the length of the super exchange pathway (R).…”

“…4 The pyridine-based bridging ligands have been actively utilized as construction units to obtain lots of supramolecular arrays and molecular magnetic materials. [5][6][7] Furthermore, the weak forces such as hydrogen bonding, van der Waals forces, π-π interactions and dipole-dipole interactions are very common in constructing these types of systems. [8][9][10][11] The small changes in structure can have important effects on the magnetic properties of these systems.…”