Single crystal X-ray structure determination and temperature-dependent structural studies of the smectogenic compound 7OS5

Abstract

Structural characteristics of solid and liquid crystalline phases of 7OS5 (4-n-pentylphenyl-4′-n-heptyloxythiobenzoate), the achiral smectogenic mesogen with the shortest terminal carbon chain in the nOS5 homologous series, are studied by complementary methods. Simultaneously perfomed X-ray diffraction and differential scanning calorimetry occur to be a powerful tool to study metastable phases. The single crystal structure of a high-temperature phase, supercooled from the room temperature down to −183°C [orthorhombic crystal system; space group Pca21; a = 54.285 (5) Å, b = 5.5843 (3) Å, c = 14.841 (1) Å, Z = 8] is determined. Lamellar ordering of elongated molecules is stabilized by hydrogen bonds . Temperature dependence of unit-cell parameters in two crystal phases as well as structural parameters of liquid crystalline phases (smectic layer spacing, tilt angle, average distance between the long axes of molecules and correlation lengths) are determined by X-ray diffraction. The obtained results are compared with the data available for other compounds in the nOS5 homologous series.

Crystallization kinetics of (S)-4′-(1-methylheptyloxycarbonyl)biphenyl-4-yl 4-[4-(2,2,3,3,4,4,4-heptafluorobutoxy)but-1-oxy]-2-fluorobenzoate

“…31.7 and 33.7–34.1 Å, have the lamellar structure, which is often observed also for other smectogens in the crystal state. 44–46 In the pristine sample, the molecules are likely tilted in the layers, although by a smaller angle than in the SmC A * phase, while in the crystal phase formed from the melt, the long axes of molecules are rather orthogonal to the layer plane. As our XRD setup does not provide high cooling rates, this method cannot investigate the partial crystallization accompanied by vitrification of the SmC A * phase.…”

Structural Study of Nematogenic Compound 5OS5

“…They are also subjects of ongoing basis studies, as new types of the nematic phase are searched for, e.g., biaxial or twist-bend nematics [6][7][8]. S-(4-pentylphenyl) 4-(alkyloxy)benzothioates (Figure 1b) are the homologous series known from their mesomorphic properties, which depend on the length of the C n H 2n+1 chain [9][10][11][12][13][14][15][16][17][18][19]. They were tested as components of mixtures with other liquid crystals, e.g., [19].…”

“…They were tested as components of mixtures with other liquid crystals, e.g., [19]. Homologues with n = 4-6 show only the nematic phase and longer homologues with n = 7-12 exhibit also the smectic C phase (n = 7) or a few smectic phases (n = 8-12) [9][10][11][12][13][14][15][16][17][18][19] with the lamellar order [1,2]. For the homologues with n = 4-7, crystal structures were solved by single-crystal X-ray diffraction (XRD) [14][15][16][17].…”

“…Homologues with n = 4-6 show only the nematic phase and longer homologues with n = 7-12 exhibit also the smectic C phase (n = 7) or a few smectic phases (n = 8-12) [9][10][11][12][13][14][15][16][17][18][19] with the lamellar order [1,2]. For the homologues with n = 4-7, crystal structures were solved by single-crystal X-ray diffraction (XRD) [14][15][16][17]. While, for n = 7, the crystal phase and both liquid crystalline phases (nematic and smectic C) were investigated by XRD at various temperatures [14], for n = 4-6, as far as we are aware, only the XRD results at room temperature were published [15][16][17].…”

“…For the homologues with n = 4-7, crystal structures were solved by single-crystal X-ray diffraction (XRD) [14][15][16][17]. While, for n = 7, the crystal phase and both liquid crystalline phases (nematic and smectic C) were investigated by XRD at various temperatures [14], for n = 4-6, as far as we are aware, only the XRD results at room temperature were published [15][16][17]. Herein, we present the structural investigations by XRD for the S-(4-pentylphenyl) 4-(pentyloxy)benzothioate Crystals 2024, 14, 367 2 of 12 compound, with n = 5, abbreviated either as 5S5 or 5OS5 (used in this paper).…”