Influence of nitrogen donor ligands on the coordination modes of copper(ii) 2-nitrobenzoate complexes: structures, DFT calculations and magnetic properties

Abstract

Three novel copper(II) 2-nitrobenzoate complexes, [Cu(g-pic) 2 (2-nitrobenzoate) 2 ] 1, [Cu(b-pic) 2 (2-nitrobenzoate) 2 (H 2 O) 2 ] 2 and [Cu 2 (H 2 tea) 2 (2-nitrobenzoate) 2 ]Á2(H 2 O) 3 (where g-pic = 4-methylpyridine, b-pic = 3-methylpyridine and H 2 tea = mono deprotonated triethanolamine), were isolated by addition of g-pic, b-pic and H 3 tea to the hydrated copper(II) 2-nitrobenzoate, [Cu 2 (2-nitrobenzoate) 4 (H 2 O) 2 ]Á2H 2 O, suspended in a methanol : water (4 : 1) mixture. The newly synthesized complexes have been characterized by elemental analyses, thermogravimetric analysis (TGA), spectroscopic techniques (EPR, IR and UV/Visible), magnetic susceptibility measurements, single crystal X-ray structure determination and DFT study. All compounds crystallize in the monoclinic crystal system with the P2 1 /c space group. X-ray structure determination revealed the presence of monomers in both 1 and 2 and dimer in 3 with the deprotonated oxygen atom of the H 2 tea ligand bridging two Cu(II) atoms. Two co-crystallized water molecules are also present in 3. The crystal lattice is stabilized by C-HÁ Á ÁO hydrogen bonding interactions in 1 and O-HÁ Á ÁO, C-HÁ Á ÁO hydrogen bonding interactions in 2 and 3. The dimeric complex exhibits relatively strong ferromagnetic exchange with J = À100 cm À1 (corresponding to H = JS 1 S 2). The zero-field splitting parameters (zfs) of the dimer triplet states D and E were derived from HF EPR spectra recorded at moderately low temperatures. The sign of D was determined from low-temperature HF EPR spectra.

Metal–Metal Interactions in Trinuclear Copper(II) Complexes [Cu3(RCOO)4(H2TEA)2] and Binuclear [Cu2(RCOO)2(H2TEA)2]. Syntheses and Combined Structural, Magnetic, High-Field Electron Paramagnetic Resonance, and Theoretical Studies

“…In polynuclear copper(II) complexes there are two contributions to the zero-field splitting, one of which is caused by the magnetic dipole-dipole interaction and the other one is due to the anisotropic exchange interactions: [27][28][29] (16) The theory of the latter has been in progress recently. 32 To estimate the exchange contribution, the dipolar part must be subtracted from the experimental zfs parameters (see last 2 columns of Table 4).…”

“…32 To estimate the exchange contribution, the dipolar part must be subtracted from the experimental zfs parameters (see last 2 columns of Table 4). The largest component of the dipole-dipole interaction tensor is along the Cu-Cu direction, while the largest component of the exchange-related zfs interaction is expected to be parallel to the direction of g z , [27][28][29][30][31][32] which in our dimeric complexes is roughly perpendicular to the Cu-Cu vector. When that direction is labeled "Z" and that of the C-Cu vector is "X" then the expressions for D dip and E dip (referred to the giant spin Hamiltonian) are 33…”

A Family of [Zn6] Complexes from the Carboxylate-Bridge-Supported Assembly of [Zn2] Building Units: Synthetic, Structural, Spectroscopic, and Systematic Biological Studies

“…Consequently, the DTA peaks at T max = 287 °C (strongly exothermic), T min = 325 °C (strongly endothermic), 510 °C (weakly endothermic), 703 °C (strongly endothermic), and 835 °C (weakly endothermic), associated with the multistep thermal decomposition processes, are observed. For all three complexes, the remaining mass indicates the formation of Na 2 O and ZnO as the possible final residues. , In the literature, analogous thermal properties have been reported showing the removal of coordinated/uncoordinated H 2 O/MeOH and CO 2 gases exhibiting endothermic reactions from carboxylate-based compounds. ,− …”

Relation between molecular structure of smectite and liquefaction of mudstone

“…The nal state of argillization (Fig. 12) occurs when the ssures that develop in the rock mass are activated under the dynamic forces applied during the excavation; 30,31 as the ssures join and converge they form large ssures that act as channels for the permeating water. When the original mudstone is saturated, the water molecules within the crystalline layers move by random Brownian movement and exchange energy with the skeleton molecules of the smectite.…”