Anju Saini

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

Three novel copper(II) 2-nitrobenzoate complexes, [Cu(γ-pic)2(2-nitrobenzoate)2] 1, [Cu(β-pic)2(2-nitrobenzoate)2(H2O)2] 2 and [Cu2(H2tea)2(2-nitrobenzoate)2]·2(H2O) 3 (where γ-pic = 4-methylpyridine, β-pic = 3-methylpyridine and H2tea = mono deprotonated triethanolamine), were isolated by addition of γ-pic, β-pic and H3tea to the hydrated copper(II) 2-nitrobenzoate, [Cu2(2-nitrobenzoate)4(H2O)2]·2H2O, 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 P21/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 H2tea ligand bridging two Cu(II) atoms. Two co-crystallized water molecules are also present in 3. The crystal lattice is stabilized by C–H⋯O hydrogen bonding interactions in 1 and O–H⋯O, C–H⋯O hydrogen bonding interactions in 2 and 3. The dimeric complex exhibits relatively strong ferromagnetic exchange with J = −100 cm−1 (corresponding to H = JS1S2). 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.

Magnetic behaviour vs. structural changes in an isomeric series of binuclear copper(II) complexes: an experimental and theoretical study

In an endeavor to study how a polydentate nitrogen donor ligand affects the magnetic properties of copper(II) methoxybenzoates, three novel complexes of copper(II) were investigated. [Cu2(H2tea)2(o-methoxybenzoate)2], [Cu2(H2tea)2(m-methoxybenzoate)2]·2H2O and [Cu2(H2tea)2(p-methoxybenzoate)2]·2H2O (where H2tea = mono-deprotonated triethanolamine) were synthesized by addition of triethanolamine (H3tea) to the hydrated Cu(o-,m-,p-methoxybenzoates)2. The newly synthesized complexes have been characterized by elemental analyses, spectroscopic techniques (electronic and FT-IR), magnetic moment determination, molar conductance studies, TGA, and single crystal X-ray determination. The experimental characterization was integrated with the ab initio theoretical determination of the magnetic coupling constant value and with the analysis of the correlation between this value and the relevant geometrical parameters. Variable temperature solid state magnetization measurements and ab initio calculations indicate a remarkable ferromagnetic coupling of the unpaired electrons centered on the two Cu atoms for the m- and p-methoxybenzoate complexes (J = 100.9 cm−1), while a non-negligible antiferromagnetic coupling is found for the third complex (J = −83.1 cm−1). This differential behaviour can be rationalized on the basis of the out-of-plane displacement (τ) of the alkoxo group with respect to the molecular Cu2O2 plane. Large τ values prevent an efficient overlap between the O 2p and the magnetic Cu 3dx2−y2, favouring a ferromagnetic coupling between the Cu sites.

Reactions of fluorinated acid anhydrides with metal alkoxides

Abstract Metal alkoxides M(OR) 4 (where MTi or Zr and Rmethyl or ethyl) have been reacted with trifluoroacetic, trifluoromethanesulfonic and fluorosulfonic anhydrides. The methoxides yielded disubstituted derivatives in all cases, whereas the ethoxides gave different products. In this way new compounds, i.e. Zr(OCH 3 ) 2 (O 2 CCF 3 ) 2 , Ti(OCH 3 ) 2 (O 2 CCF 3 ) 2 , Ti 2 O(O 2 CCF 3 ) 6 , Zr(OCH 3 ) 2 (O 3 SCF 3 ) 2 , Ti(OC 2 H 5 ) 2 (O 3 SCF 3 ) 2 , Zr(OCH 3 ) 2 (O 3 SF) 2 and Ti(OC 2 H 5 ) 2 (O 3 SF) 2 , have been isolated in nearly quantitative yield. These reactions also provide an alternative route for the synthesis of previously known compounds Zr(O 2 CCF 3 ) 4 and Zr(O 3 SCF 3 ) 4 . The products have been characterised by elemental analysis, infrared and NMR ( 1 H and 19 F) spectroscopy and molecular weight determination.