Attractive and repulsive forces in a crystal of [Rb(18-crown-6)][SbCl6] under high pressure

The compression behavior of [Rb(18-crown-6)][SbCl6] crystal under pressure up to 2.16   (3)   GPa was investigated in a diamond anvil cell (DAC) using a mixture of pentane – isopentane (1:4) as the pressure-transmitting fluid. The compound crystallizes in trigonal space group R3 and no phase transition was observed in the indicated pressure range. The low value of pressure bulk modulus [9.1   (5)   GPa] found in this crystal is a characteristic of soft materials with predominant dispersive and electrostatic interaction forces. The nonlinear relationship between unit-cell parameters under high pressure is attributed to the influence of reduced intermolecular H...Cl contacts under pressure over 0.73   GPa. It also explains the high compression efficiency of [Rb(18-crown-6)][SbCl6] crystals at relatively low pressures, resulting in a significant shift of the Rb atom to the center of the crown ether cavity. At pressures above 0.9   GPa, steric repulsion forces begin to play a remarkable role, since an increasing number of interatomic H...Cl and H...H contacts become shorter than the sum of their van der Waals (vdW) radii. Below 0.9   GPa, both unit-cell parameter dependences (P – a and P – c) exhibit hysteresis upon pressure release, demonstrating their influence on the disordered model of Rb atoms. The void reduction under pressure also demonstrates two linear sections with the inflection point at 0.9   GPa. Compression of the crystal is accompanied by a si...

Source: Acta Crystallographica Section B - March 20, 2024 Category: Chemistry Authors: Rusanov, E.B. W ö rle, M.D. Kovalenko, M.V. Domasevitch, K.V. Rusanova, J.A. Tags: X-ray diffraction high pressure crown ether attractive and repulsive forces alkali metal complexes research papers Source Type: research