Asma Khurshid
Pakistan Institute of Engineering and Applied Sciences, Pakistan
Title: A close insight into the nature of intra and intermolecular interactions in 1-acyl thioureas and dihydropyrimidine-2-(1H) thione derivatives using single crystal X-ray crystallography and related techniques
Biography
Biography: Asma Khurshid
Abstract
Single crystal X-ray crystallographic studies has been carried out in order to explore the nature of intra- and inter molecular interaction in 1-(4-chlorobenzoyl)-3-(2-methyl-4-oxopentan-2-yl) thiourea, 1-(2-chlorobenzoyl)thiourea and for the following derivatives of 1-(R-phenyl)-4,4,6-trimethyl-3,4-dihydropyrimidine-2(1H)-thione i.e., R = 2-chloro (1), 2,3-di-chloro (2), 2,4-di-methyl (3), and 4-methoxy (4). This study has also been supported by vibrational analysis (FT-IR, FT-Raman) in addition to Topological and Hirshfield surface analysis which give a visual three-dimensional picture of the nature of intermolecular interactions in case of the newly synthesized dihydropyrimidine-2-(1H) thione derivatives.
The synthesis of 1-(4-chlorobenzoyl)-3-(2-methyl-4-oxopentan-2-yl) thiourea was carried out with particular focus to investigate the effect exerted by competing intramolecular C=O….H-N bonds in the molecular structure. The molecular and X-ray crystal analysis of this compound revealed the preferential existence of S conformer over U conformer with the C=O and C=S bonds pointing in opposite directions.The application of vibrational analysis in addition to crystal studies for the newly synthesized 1-(2-chlorobenzoyl)thiourea indicated the presence of extended N–H….S=C hydrogen-bonding networks between both the carbamide (NH2) and thioamide (N–H) groups and the thiocarbonyl bond (C=S) that are significant for crystal packing in its structure.The detailed crystal structure analysis revealed that the four studied dihydropyrimidine-2-(1H)-thione derivatives attain the following canonical conformations: (1) 2S1 screw-boat form; (2) E2 envelope; (3) Intermediate between 6S1 screw-boat and 6H1 half-chair form; (4) E4 envelope. While the topological analysis of the electron densities highlights the importance of dominant N-H…S interactions for stabilization of crystal packing in all four derivatives studied.