• Vivek K Gupta

      Articles written in Bulletin of Materials Science

    • Supramolecular structure of S-(+)-marmesin-a linear dihydrofuranocoumarin

      Sanjeev Goswami Vivek K Gupta Ashok Sharma B D Gupta

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      The title compound, C14H14O4, a linear dihydrofuranocoumarin, was isolated from the bark of Aegle marmelos, a plant widely used in Ayurvedic system of medicine for the treatment of various ailments. The crystal structure was determined from X-ray diffraction data using direct methods. The compound crystallizes into monoclinic space group 𝑃21 with unit cell parameters: 𝑎 = 5.721(1) Å, 𝑏 = 13.810(1) Å, 𝑐 = 7.864(2) Å, 𝛽 = 100.39(1)°, 𝑍 = 2. The structure was refined by full-matrix least-squares to a final 𝑅 value of 0.0523 for 1184 observed reflections. The benzopyran moiety is perfectly planar. The dihedral angle between the pyrone and benzene rings is 0.3(1)°. The furan ring has a 2𝛼-envelope conformation. The molecules are linked by O–H…O hydrogen bonds into chains and these chains are linked into sheets by C–H…O hydrogen bonds. Further, the 𝜋−𝜋 stacking and C–H$\ldots\pi$(arene) interactions link all of the sheets into a supramolecular structure.

    • X-ray study of weak interactions in two flavonoids

      Deepak Sharma Vivek K Gupta Goutam Brahmachari Sadhan Mondal Arindam Gangopadhyay

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      X-ray diffraction studies were carried out on single crystals of two flavonoids, viz. 5-hydroxy-6,7,4′-trimethoxyflavone, C18H16O6, (I) and 5-hydroxy-3,7,4′-trimethoxyflavone, C18H16O6, (II). Crystal structures of both the flavonoids were solved by direct methods and refined by full-matrix least-squares procedures. In both the molecules, the benzopyran moiety is planar. The dihedral angle between the phenyl ring and the benzopyran portion is 5.50(4)° in (I) and 29.11(5)° in (II). In (I), the crystal packing is influenced by O–H…O hydrogen bonds, and weak C–H…O and $\pi \ldots \pi$ interactions whereas in (II) the crystal structure is stabilized by the presence of four intermolecular short contacts of the type C–H…O. There is also one C–H$\ldots \pi$ hydrogen bond with H… centroid distance of < 2.7 Å. The molecules are further stabilized by 𝜋–𝜋 interactions.

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