Crystal structure and magnetic susceptibility of copper (II) chloride tetramethylsulfoxide [CuCl2(TMSO)] and copper (II) chloride monodimethylsulfoxide [CuCl2(DMSO)]: Ferromagnetic spin-½ Heisenberg linear chains

Abstract

The crystal structures of the title compounds [${\mathrm{C}}_{4}$${\mathrm{H}}_{8}$SO (TMSO), ${\mathrm{C}}_{2}$${\mathrm{H}}_{6}$SO (DMSO)] have been determined. The TMSO salt is orthorhombic [space group $\mathrm{Pbca}$, $a=13.844(10)$, $b=6.418(12)$, and $c=17.480(16)$ \AA{}] while the DMSO salt is monoclinic [space group $\frac{P{2}_{1}}{c}$, $a=7.774(1)$, $b=13.557(3)$, $c=6.475(1)$ \AA{}, and $\ensuremath{\beta}=103.83(1)\ifmmode^\circ\else\textdegree\fi{}$]. Each contain linear chains of Cu ions with three bridging ligands (2 C1, 1 O) between each pair of Cu ions. The bridging Cu-$L$-Cu angles are \ensuremath{\sim} 87\ifmmode^\circ\else\textdegree\fi{} for the symmetrical bridges and \ensuremath{\sim} 80\ifmmode^\circ\else\textdegree\fi{} for the asymmetrical bridges. In each salt, the copper coordination geometry is severely distorted from octahedral with four short Cu-ligand bonds (three chlorine and one oxygen) and two long Cu-ligand bonds (one chlorine and one oxygen). Adjacent chains are well isolated from each other by the sulfoxide groups in one direction, but short sulfur-sulfur contacts occur between adjacent chains in the other direction. The susceptibility of the salts has been measured between 2.0 and 300 K on a PAR vibrating-sample magnetometer and on a Faraday balance. The high-temperature data show positive deviation from Curie behavior, indicative of ferromagnetic coupling. However, considerable magnetic interactions between chains exist and the $\ensuremath{\chi}T$ vs $T$ plots show maxima at low temperature. The data have been analyzed with several one-dimensional models. The best fit is obtained with an Heisenberg linear chain with ferromagnetic interaction ($\frac{J}{k}=39\ifmmode^\circ\else\textdegree\fi{}$K, TMSO; $\frac{J}{k}=45\ifmmode^\circ\else\textdegree\fi{}$K, DMSO) with a mean-field correction for the antiferromagnetic interchain interactions ($\frac{Z{J}^{\ensuremath{'}}}{k}=\ensuremath{-}1.6\ifmmode^\circ\else\textdegree\fi{}$K, TMSO; $\frac{Z{J}^{\ensuremath{'}}}{k}=\ensuremath{-}4.0\ifmmode^\circ\else\textdegree\fi{}$K, DMSO). Thus, the relevant ratio defining the ideality of the system, $\frac{J}{{J}^{\ensuremath{'}}}$, is \ensuremath{\sim} 50 for the TMSO salt and \ensuremath{\sim} 25 for the DMSO salt.