Ranganathan Sathishkumar

Publications (6)1.8 Total impact

• Article: Crystal packing and melting temperatures of small oxalate esters: the role of C-H···O hydrogen bonding.

  Sumy Joseph, Ranganathan Sathishkumar, Sudarshan Mahapatra, Gautam R Desiraju
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  ABSTRACT: The simple dialkyl oxalates are generally liquids at room temperature except for dimethyl and di-tert-butyl oxalate which melt at 327 and 343 K. The crystal structures of diethyl, di-iso-propyl, di-n-butyl, di-tert-butyl and methyl ethyl oxalates were determined. The liquid esters were crystallized using the cryocrystallization technique. A comparison of the intermolecular interactions and packing features in these crystal structures was carried out. The crystal structure of dimethyl oxalate was redetermined at various temperatures. The other compounds were also studied at several temperatures in order to assess the attractive nature of the hydrogen bonds therein. A number of moderate to well defined C-H···O interactions account for the higher melting points of the two solid esters. Additionally, a diminished entropic contribution ΔS(m) in di-tert-butyl oxalate possibly increases the melting point of this compound further.
  Acta crystallographica. Section B, Structural science 12/2011; 67(Pt 6):525-34. · 1.80 Impact Factor
• Article: Structural Variability in the Monofluoroethynylbenzenes Mediated through Interactions Involving “Organic” Fluorine

  Amol G. Dikundwar, Ranganathan Sathishkumar, Tayur N. Guru Row, Gautam R. Desiraju
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  ABSTRACT: Competition among weak intermolecular interactions can lead to polymorphism, the appearance of various crystalline forms of a substance with comparable cohesive energies. The crystal structures of 2-fluorophenylacetylene (2FPA) and 3-fluorophenylacetylene (3FPA), both of which are liquids at ambient conditions, have been determined by in situ cryocrystallization. Both compounds exhibit dimorphs, with one of the forms observed in common, P21, Z = 2 and the other form being Pna21, Z = 4 for 2FPA and P21/c, Z = 12 for 3FPA. Variations in the crystal structures of the dimorphs of each of these compounds arise from subtle differences in the way in which weak intermolecular interactions such as C–H···π and C–H···F are manifested. The interactions involving “organic” fluorine, are entirely different from those in the known structure of 4-fluorophenylacetylene (4FPA), space group P21/c, Z = 4. The commonalities and differences in these polymorphs of 2FPA and 3FPA have been analyzed in terms of supramolecular synthons and extended long-range synthon aufbau module (LSAM) patterns. These structures are compared with the three polymorphs of phenylacetylene, in terms of the T-shaped C–H···π interaction, a feature common to all these structures.
  07/2011;
• Article: Third Polymorph of Phenylacetylene

  Tejender S. Thakur, Ranganathan Sathishkumar, Amol G. Dikundwar, Tayur N. Guru Row, Gautam R. Desiraju
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  ABSTRACT: A third polymorph of phenylacetylene (Z′ = 6), which is obtained by quenching the liquid, shows some similarities to the two earlier known forms, and the adoption of a high Z′ value in this crystal form is discussed.
  Crystal Growth & Design. 01/2010; 10:4246-4249.
• Article: Directing role of functional groups in selective generation of C–Hπ interactions: In situ cryo-crystallographic studies on benzyl derivatives

  Susanta K. Nayak, Ranganathan Sathishkumar, T. N. Guru Row
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  ABSTRACT: The in situ cryo-crystallization study of benzyl derivatives reveals that the molecular packing in these compounds is either through methylene (sp3)C–Hπ or aromatic (sp2)C–Hπ interactions depending on the level of acidity of the benzyl proton. These studies of low melting compounds bring out the subtle features of such weak interactions and point to the directional preferences depending on the nature (electron withdrawing, polarizability) of the neighbouring functional group.
  CrystEngComm. 01/2010; 12:3112-3118.
• Article: Directing role of functional groups in selective generation of C-H center dot center dot center dot pi interactions: In situ cryo-crystallographic studies on benzyl derivatives

  Susanta K Nayak, Ranganathan Sathishkumar, Guru TN Row
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  ABSTRACT: The in situ cryo-crystallization study of benzyl derivatives reveals that the molecular packing in these compounds is either through methylene (sp(3)) C-H center dot center dot center dot pi or aromatic (sp(2)) C-H center dot center dot center dot pi interactions depending on the level of acidity of the benzyl proton. These studies of low melting compounds bring out the subtle features of such weak interactions and point to the directional preferences depending on the nature (electron withdrawing, polarizability) of the neighbouring functional group.
• Article: Dimorphism and structural modulation in quinoxaline

  Ranganathan Sathishkumar, Sudarshan Mahapatra, Tejender S Thakur, Gautam R Desiraju
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  ABSTRACT: The Z' = 1 and Z' = 5 structures of quinoxaline are compared. The nature of the intermolecular interactions in the Z' = 5 structure is studied by means of variable-temperature single-crystal X-ray diffraction. The C-H center dot center dot center dot N and pi ... pi it interactions in these structures are of a stabilizing nature. The high Z' structure has the better interactions, whereas the low Z' structure has the better stability. This trade-off is a recurrent theme in molecular crystals and is a manifestation of the distinction between thermodynamically and kinetically favoured crystal forms.