ABSTRACT
Liquid chalcogen-halogen A2X2 (A: S, Se, X: Cl, Br) is a racemic mixture of enantiomers between left-handed (L) and right-handed (D) chiral molecules. The lone-pair orbital of the chalcogen atom significantly affects the molecular conformation and intermolecular interaction. The latter depends on the size of the orbital and number density. High-energy X-ray diffraction measurements and reverse Monte Carlo (RMC) structural modelling were performed for liquid S2Cl2 in addition to the previous structural analysis for liquid Se2Br2. By comparing the structures of the RMC model and hard-sphere Monte Carlo (HSMC) model, the effect of refinement on the experimental structure factor can be analysed. In this paper, nearest-neighbour intermolecular pairs are classified in terms of enantiomer pairs such as like-pair (L-L and D-D) and unlike-pair (L-D). As a result, the effect of a strong intermolecular attractive interaction is detected in Se2Br2 as increasing the number of like-pairs with geometrical advantages from HSMC to RMC, whereas that of an intermolecular repulsive interaction is observed in S2Cl2 as elongation of the averaged intermolecular S-S distance from HSMC to RMC. These results are consistent with the results of the ab initio molecular dynamics simulation for Se2Cl2 and S2Cl2.
Acknowledgements
High-energy X-ray diffraction measurements were performed at the BL04B2 beamline at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal No. 2004B0629 and 2010A1541).
Disclosure statement
No potential conflict of interest was reported by the author.