Chemical Crystallography and Materials Design
The main emphasis of the group is centered on synthesis, structural characterization and deriving inputs for futuristic materials design. The understanding of intra and intermolecular interactions forms the central theme of all our studies. The approach is through the following subheads.
A. Charge density analysis in molecular crystals
Experimental electron density features obtained based on high resolution single crystal X-ray diffraction data sets at low temperatures are compared with high level theoretical calculations. Some of the major results include (i) Characterization and identification of the region of overlap between hydrogen bonds and van der Waals interactions (ii) Quantitative identification of the proton transfer region in salts and cocrystals in salt-cocrystal continuum,(ii) Evaluation of intermolecular interactions involving “organic fluorine”,(iii) Halogen bonding, interhalogen and interchalcogen interactions as structure directing components in crystal engineering. A new approach “Synthon Based Fragment Approach (SBFA)” has been developed for allowing the transferability of charge densities between molecules with possible extension to biological macromolecules.
Structural features of several compounds which are liquids at room temperature have been characterized using this unique technique by growing single crystals at low temperatures. This approach allows for different rates in cooling thus providing pathways for generation and fine tuning of polymorphic modification in these materials. Controlled generation of suitable polymorphs in drugs and pharmaceuticals and in particular synthesis and structure of pharmaceutical cocrystals to gain insights into design and fabrication of new drug forms is the primary target of this approach.
C. Phase transitions in inorganic compounds: Applications in photodegradation, fast ion conduction and catalysis
Search for new generation materials using temperature assisted phase transitions in several complex oxides, sulphates, phosphates, vanadates and tantalates have led to both understanding at a fundamental level and has allowed for the generation of functional materials. The focus has been on properties like second harmonic generation, photocatalytic properties, high ionic conductivity and ferroelectricity. Recently, designed structural modification on sulfate minerals which are abundantly available in earth crust, have resulted the generation of functional materials.
D. Ab initio structure determination by XRPD: Profile and Reitveld refinement
E. Quantum chemical periodic calculations and crystal structure prediction
Ab-initio calculations of ground state energy, electronic wave functions and various properties (cohesive energy, band structure and polarizability) of 0D to 3D periodic systems using CRYSTAL package which incorporates the crystallographic symmetry and periodicity. Accurate estimation of the theoretical charge densities and apriori prediction of the crystal structures of organic compounds is being pursued
- Venkatesha R. Hathwar, Tejender S Thakur, Tayur N. Guru Row and Gautam R. Desiraju “Transferability of multipole charge density parameters for supramolecular synthons: A new tool for quantitative crystal engineering” Cryst. Growth Des. 2011, 11, 616-623.
- Venkatesha R. Hathwar and Tayur N. Guru Row “Charge density analysis of hetero-halogen (Cl∙∙∙F) and homo-halogen (F∙∙∙F) intermolecular interactions in molecular crystals: Importance of the extent of polarizability” Cryst. Growth Des. 2011, 11, 1338−1346.
- Amol G. Dikundwar, Ch. Venkateswarlu, Ross O. Piltz, Srinivasan Chandrasekaran and Tayur N. Guru Row “Crystal structures of fluorinated aryl biscarbonates and a biscarbamate: a counterpoise between weak intermolecular interactions and molecular symmetry” CrystEngComm 2011, 13, 1531-1538.
- Dipankar Saha, Giridhar Madras and Tayur N. Guru Row “Manipulation of the hydration Levels in Minerals of Sodium Cadmium Bisulfate toward the Design of Functional Materials” Crystal Growth & Design, (accepted).
- Prangya Parimita Sahoo and Tayur N. Guru Row “Crystal Chemistry of the Noncentrosymmetric Eulytites: A3Bi(XO4)3 (X = V, A = Pb; X = P, A = Ca, Cd, Sr, Pb)” Inorg. Chem. 2010, 49, 10013-10021.