A study of the bis(4-chlorophenyl) sulphide by 35Cl nuclear quadrupole resonance and ab initio calculations

Abstract

As an extension of previous works in sulphur-substituted biphenyls, a complete pulsed 35Cl nuclear quadrupole resonance (NQR) study of the bis(4-chlorophenyl) sulphide compound is presented. In order to characterize the structural thermal behaviour of the solid phase, the NQR spectra and spin-lattice relaxation times were recorded from 80 K to 330 K. In addition, ab initio calculations at HF/3-21G* and 6-31G* levels were performed in order to obtain information about the equilibrium geometry and the torsional potential of the free bis(4-chlorophenyl) sulphide molecule. The NQR study results show that the title compound presents a unique stable crystalline phase in the scanned temperature range. This phase diagram contrasts notably with those observed at the same temperatures in bis(4-chlorophenyl) sulphone and bis(4-chlorophenyl) sulphoxide, which show an incommensurate phase transition and two-phase coexistence, respectively. The narrow NQR line observed suggests that the 35Cl atoms in the unit cell are in crystallographic equivalent positions. Ab initio calculations for the free molecule show that the symmetry point group is C2 and the dihedral angle is 60°. The results are discussed and compared with the known information about the sulphone and sulphoxide derivatives. The effect of the interphenyl linking group is also discussed, in order to understand the evolution of the phase diagram in this group of compounds.