Structure-Property Relationships in Crystal Structures of Polar Molecules

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

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

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

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

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

Spartan Results

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

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

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