Electrostatic properties of cyano-containing mesogens

We analyse the electrostatic properties of a set of cyano-containing mesoge n molecules with different rigid cores and variable alkyl chain lengths, co mputing the molecular charge distributions. Using the simple prototype benz onitrile, we analyse the reliability of the quantum chemical methods used t o estimate the electrostatic dipole moments of polar conjugated molecules. We show that the electronic properties of the long mesogenic molecules can be treated by combining HF geometry optimization procedures with single poi nt MP2 calculations. We compare the results of these computations with the available experimental phase transition data of mesogens and discuss some e xamples of how the non-trivial mesomorphic behaviour, which is usually obse rved in these cyano compounds, can be qualitatively explained by the molecu lar electrostatic interaction potential.