National Chemical Laboratory
Publication and Science Communication Unit
14 June 2006
Single Crystal X-ray Diffractometer User’s Workshop
National Chemical Laboratory (NCL), Pune organized a three-day
“Bruker-AXS single crystal X-ray diffractometer user’s workshop 2006”
from 30 May to 1 June 2006. Bruker AXS, The Netherlands, sponsored
the workshop.
NCL was the first laboratory to acquire SMART APEX 1:1 CCD single
crystal X-ray diffractometer with latest technology. There are eight
such single crystal X-ray diffractometers in the country and the
number is growing. The purpose of the workshop was to give handson experience on the latest software to the user and also to discuss
the problems faced by researchers. This was second workshop in the
series. About forty participants from IITs, CSIR laboratories, R&D
institutes and Universities from various parts of the country attended
the workshop.
Dr.
(Mrs.)
Vedavati
G.
Puranik,
Scientist,
Center
for
Material
Characterization, NCL, shared her experience on SMART APEX with the
audience. Dr. B.D. Kulkarni, Deputy Director, NCL, inaugurated the
workshop. Prof. T.N. Guru Row, Chairman, Solid State and Structural
Chemistry Unit, IISc, Bangalore delivered the inaugural talk on
“Charge
density
analysis
intermolecular interactions”.
on
molecular
crystals:
Insights
into
In his inaugural address Prof. Guru Row spoke about one-electron
properties, intermolecular interactions in terms of the atoms in
molecule, visualizing mapping electron densities etc. He explained the
possibility
of
collecting
the
precise
and
accurate
data
at
low
temperature with the help of SMART APEX single crystal X-ray
diffractometer. He elaborated the use of “atom in molecule” approach
with special emphasis on improvements in charge density models. He
also illustrated the developments in both experimental and theoretical
techniques to interpret and analyze the nature of weak intermolecular
interactions. He also showed the appearance of a "region of overlap"
to segregate hydrogen bonds from van der Waals interactions based
on the criteria proposed by Koch and Popelier. He gave the examples
of coumarin and its derivatives for identifying differences in energy
surfaces in concomitant polymorphs.
In another invited talk, Prof. A. Nangia, School of Chemistry, Central
University,
Hyderabad
spoke
on
“Conformational,
concomitant
polymorphs: Multiple molecules, kinetic and thermodynamic factors,
and polymorph control”. Starting with the importance of polymorphism
in organic crystals and pharmaceuticals, Prof. Nangia discussed
different types of polymorphism and methods of establishing it. He
elaborated on the Host-Guest inclusion compounds, H-bonding and
intermolecular interactions and how they can be different in different
polymorphs. Usefulness of various methods like Powder X-ray, TGA
and DSC to identify different types of polymorphs was shown with the
help of experiments carried out in his lab. He touched upon the
controversy in naming solvated crystals and pseudopolymorphs. He
also showed the fundamental understanding of crystallization and new
pharmaceutical phases.
The hands-on training using latest software was organized at the
computer laboratory of Digital Information Resource Center of NCL.
Dr. Leo Starver, Application Scientist of Bruker-AXS B. V., The
Netherlands conducted the training programme.