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Crystals 2012, 2(3), 1347-1356;

Temperature-Dependent Ordering of the Methyl Group in the Crystal Structure of 5-(2-Chlorophenyl)-7-ethyl-1H-thieno [2,3-E][1,4]diazepin-2(3H)-one

Department of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland
Department of Studies in Chemistry, University of Mysore, Mysore-570 006, India
R. L. Fine Chem., Bangalore-560 064, India
Author to whom correspondence should be addressed.
Received: 15 May 2012 / Revised: 23 July 2012 / Accepted: 26 July 2012 / Published: 18 September 2012
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5-(2-Chlorophenyl)-7-ethyl-1H-thieno[2,3-e][1,4]diazepin-2(3H)-one, a close analogue of clotiazepam (full agonist at GABA receptor), crystallizes in monoclinic P21/c space group with a = 15.6941(6) Å, b = 10.7909(4) Å, c = 8.6586(3) Å, and β = 102.184(4)° (at 125 K). Seven-Membered diazepine ring has approximate mirror plane of symmetry, planar thieno and phenyl rings are almost perpendicular to one another, dihedral angle between their mean planes is 84.11(5)°. N–H···O hydrogen bonds connect molecules into centrosymmetric dimers which are further expanded into 3D crystal structure with the help of weaker C–H···O and C–H···π interactions. The methyl group is disordered at room temperature, but it gets gradually ordered at lower temperatures and becomes fully ordered at approximately 200 K. The changes in structure with temperature were studied between 125 and 380 K. The unit cell volume—as expected—increases almost monotonically when the temperature rises, but one of the parameters shortens significantly. View Full-Text
Keywords: diazepines; hydrogen bonding; disorder; structural change diazepines; hydrogen bonding; disorder; structural change

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Dutkiewicz, G.; Kubicki, M.; Dayananda, A.S.; Yathirajan, H.S.; Ramesha, A.R. Temperature-Dependent Ordering of the Methyl Group in the Crystal Structure of 5-(2-Chlorophenyl)-7-ethyl-1H-thieno [2,3-E][1,4]diazepin-2(3H)-one. Crystals 2012, 2, 1347-1356.

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