1. Structure-Property Relationships in Crystal Structures of Polar Molecules

2. Aims
Search for patterns in crystal structures of functionalised organic molecules
Influence of electrostatic multi-polar interactions
Part of overall group interest in crystal packing interactions
Develop procedures for design of systems with electro-optical interactions

3. Background
Nonlinear optical (NLO) materials have properties useful for photonic materials
Primary requisite for NLO material is non-centrosymmetry
Easy (relatively!) to design in at molecular level; hard to design in at macromolecular level
H-bonding less prevalent for these materials (unlike pharmaceuticals)
Thus electrostatic interactions assume relatively greater importance

4. E-Science Part of the E-science Comb-e-Chem project
Database mining to search for patterns in structures e.g. CSD
But - CSD not large enough to allow useful knowledge to be gained
So – need to accumulate new data to provide detailed information to identify patterns in structures

5. Data Set for Project
Data set of polymorphic clusters where at least one member is non-centrosymmetric
Constructed from CSD v5.23 (April 2002)
835 ‘hits’ grouped into 258 polymorphic clusters each comprising of 2-3 different polymorphs

6. Modelling of Electrostatic Potential
Model electrostatic potential map and partial charge distribution
Molecular modelling package – Spartan ’02 for Windows
Single point energy calculation using Hartree-Fock model with 3-21G(*) basis set
Computationally cheap, but may not be sophisticated enough

7. Spartan Results

8. Further Computational Modelling
Attempt to model solid state using coordination sphere failed – beyond limits of software
A set of polymorphs compared using ‘Synthon’ (Dr. T. Gelbrich)
A subset of these polymorphs compared using ‘Voron’ (Dr. S. Christensen)
‘Synthon’ data has shown similarities between some polymorphs compared
‘Voron’ data is still being analysed

9. Further Work
Coordinate data missing from CSD, so need to synthesise / recrystallise compounds to fill in gaps
Carry out further comparisons using ‘Synthon’ and ‘Voron’ in combination with electrostatic potential studies
Recrystallise compounds from data set under strong D.C. fields

10. Acknowledgements Prof. Mike Hursthouse
The Group – Prof. Chris Frampton, Dr. Simon Coles, Dr. Mark Light, Dr. Ann Bingham, Dr. Pete Horton, Dr. Thomas Gelbrich, Dr. Stefan Christensen, Dr. Yang Li, Dr. Ranko Vrlej, Dave Hughes, Suzanna Ward
EPSRC E-Science project