Structure-Property Relationships in Crystal Structures of Polar Molecules

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