75324-55-9Relevant academic research and scientific papers
Crystal structures and magnetic properties of CuX2(pdmp)2 complexes (X = Br, Cl)
Costa-Filho, Antonio J.,Munte, Claudia E.,Barberato, Claudio,Castellano, Eduarde E.,Mattioli,Calvo, Rafael,Nascimento, Otaciro R.
, p. 4413 - 4421 (2008/10/08)
We report the synthesis and the structural and magnetic characterization of two new compounds: dibromobis-(pdmp)copper(II), CuBr2C22H24N4 (1), and dichlorobis(pdmp)copper(II), CuCl2C22H24N4 (2), where pdmp = 1-phenyl-3,5-dimethylpyrazole. The structures were refined by full-matrix least-squares techniques to R1 = 0.0620 and 0.0777, respectively. Compound 1 belongs to the space group P21/n with a = 8.165(5) A, b = 10.432(3) A, c = 13.385(4) A, β = 100.12(4), and Z = 2. Compound 2 belongs to the space group P21/c with a = 8.379(2) A, b = 22.630(2) A, c = 12.256(2) A, β= 98.43(3)°, and Z = 4. It has the same molecular formula as a compound reported previously but a different crystal structure. Detailed single-crystal EPR measurements were performed for single-crystal samples of 1 and 2 at 9 and 35 GHz and at room temperature. The positions and line widths of the EPR lines were measured as a function of the magnetic field orientation in three orthogonal planes. The data were used to study the electronic properties of the copper ions and to evaluate the exchange interactions between them. Our results are discussed in terms of the electronic pathways for superexchange between copper ions, which are provided by the stacking of pyrazole and phenyl rings of neighboring molecules and by hydrogen-halogen bonds.
Pressure-induced temperature dependence of a weak exchange coupling in dichlorobis(1-phenyl-3,5-dimethylpyrazole)copper(II) crystals
Hoffmann,Goslar,Hilczer,Krupski
, p. 3554 - 3556 (2008/10/08)
X-band EPR temperature and pressure (up to 450 MPa) measurements of the dichlorobis(1-phenyl-3,5-dimethylpyrazole)copper(II) crystal show that exchange coupling between Cu(II) ions is very weak with J = 0.003 86 cm-1 at room temperature. This coupling is temperature independent but decreases under pressure. Moreover, when pressure is applied to the crystal, the J-value becomes temperature dependent and decreases on cooling. Also the gz-factor and the line width value are affected by temperature and pressure. These effects are discussed and explained as a result of a decrease of the tilt angle between the pyrazole ring and Cu(II) coordination plane under pressure and a shortening of the Cu-N bond on cooling. Exchange coupling is suggested to be ferromagnetic at normal conditions with an antiferromagnetic contribution appearing under pressure.
