Crystal structure analysis of two crystalline bis(ω-hydroxyalkoxy)biphenyls using a combination of powder diffraction, IR spectroscopy and molecular simulation

Synchrotron and standard X-ray powder diffraction (XRD) combined with IR spectroscopy and molecular simulations have been used to investigate the crystal structure of two crystalline mesogenic diols: 4,4′-bis(6-hydroxy-1-hexyloxy)biphenyl (D-I) and 4,4′-bis(11-hydroxy-1-undecyloxy)biphenyl (D-II). The crystal structure of D-I has been determined from high-resolution synchrotron powder-diffraction data collected at BM16 of the ESRF. The methods of grid search and Rietveld refinement have been used to determine this structure. The space group is Cc, with unit-cell parameters a = 44.392 (3), b = 7.221 (1), c = 6.631 (1) Å and β = 91.09 (1)°. The structure of D-II has a small degree of disorder. This structure was analyzed with a combination of experimental methods, conventional XRD, IR spectroscopy and molecular mechanics simulations, revealing the character of the structural disorder. Both the structures of D-I and D-II are lamellar-packed and layered. The hydrogen-bonding system between two adjacent layers in the structure of D-II is distorted.