Crystal structure of (4-(3,4-bis(2,5-dimethylthiophen-3-yl)- cyclopent-3-en-1-yl)phenyl)methanol, C24H26OS2

C24H26OS2, orthorhombic, Pccn (no. 56), a = 12.493(1) Å, b = 40.201(3) Å, c = 8.487(7) Å, V = 4262.5 Å, Z = 8, Rgt(F) = 0.069, wRref(F) = 0.208, T = 295 K. Source of material (4-(3,4-bis(2,5-dimethylthiophen-3-yl)cyclopent-3-en-1-yl)phenyl)methanol was synthesized by multi-step reaction [1]. Chemicals used for the synthesis were commercially available of AR grade, and were used as received without further purification. The colorless crystals of the title compound were obtained by slow evaporation of hexane solution at room temperature. Experimental details The hydrogen atoms were placed geometrically and refined using a riding model with d(C—H) = 0.93 Å (aromatic), 0.96 Å (–CH3), 0.97 Å (–CH2–) or 0.98 Å (–CH–), Uiso(H) = 1.2 1.5 Ueq(C) and d(O—H) = 0.82 Å (hydroxyl), Uiso(H) = 1.5 Ueq(O). Discussion The title crystal structure is built up from C24H26OS2 molecule (figure, top), with all the bond lengths being within normal ranges. The crystal structure displays intraand intermolecular C–H···, interactions with no hydrogen bonds and ,···, interactions being established. The title molecule has photoactive antiparallel conformations. The distances between reactive carbon atoms are short enough for photocyclization reaction: 3.565(6) Å (C5 to C20, symmetry code i: x, y, z), which is essential to the photochromic reactivity in the crystalline phase [2,3]. Upon irradiation with ultraviolet light, the colorless crystal turns yellow. The colors are due to the photogenerated closed-ring isomer. The colored crystal can sustain several days in the dark, which demonstrate its stability. Upon irradiation with visible light, the colored crystal is completely bleached and return to the initial colorless one. The antiparallel conformation is stabilized by eight of eleven intramolecular C–H···, interactions. Four C–H···, interactions are formed between methyl hydrogen atoms and two thiophene rings. In two of the bonds (C19–H19A···,, C2/C3/C4/C5/S1; C6–H6A···,, C20/C21/C22/C23/S2), the hydrogen atom is directly above the thiophene ring and the C–H bond points towards a ring carbon. This arrangement corresponds to a type-III interaction [4]. The methylene hydrogen atoms of the five membered ring also interacted with the phenyl ring and two thiophene rings formed seven type-VI C–H···, interactions. Totally eight type-III and type-V intermolecular C–H···, interactions are found in the crystal structure (figure, bottom). Typical type-V C–H···, interaction is C10–H10A···, (C12/C13/C14/ C15/C16/C17, symmetry code ii: x,1.5–y,0.5+z), in which the hydrogen atom interacts with a carbon at the edge of the acceptor ring. The H···centroid distances range from 2.985 to 3.995 Å in both intramolecular and intermolecular C–H···, interactions, which is well inside the interval classified by Malone to 2.65 to 4.00 Å, basing on a survey of Cambridge Structural Database combined with semi-empirical and ab initio molecular orbital calculations [4]. The molecules are packed together only by intermolecular C–H···, interactions which are further stabilizing the molecular conformation. Z. Kristallogr. NCS 225 (2010) 495-497 / DOI 10.1524/ncrs.2010.0217 495 © by Oldenbourg Wissenschaftsverlag, München