Dialkyl 2,2′-bipyridine-4,4′-dicarboxylate complexes of Pt^II, Cd^II and Re^I: the effects of metal centre geometry and ligand substitution on phase behaviour

Abstract

Dialkyl 2,2′-bipyridine-4,4′-dicarboxylate derivatives are non-mesogenic ligands capable of supporting liquid crystalline phase formation when coordinated with a variety of metals. Herein is described a preliminary study on altering stable temperature ranges of thermotropic mesophases through metal centre selection and ligand modification. Characterisation of non-mesogenic CdL ^{α n} Cl₂ complexes and mesogenic ReL ^{α n} (CO)₃Br and PtL ^{β n} Cl₂ derivatives are presented (L ^{α n} is the ligand with α-attachment of alkyl chains, L ^{β n} is the ligand with β-attachment of chains and n is the number of carbons in the alkyl chain). Synthetic procedures and characterisation of the products by differential scanning calorimetry, thermogravimetric analysis, polarising optical microscopy and variable temperature X-ray diffraction are presented.

Keywords:

• metallomesogen
• liquid crystal
• VT XRD
• room temperature liquid crystal

Acknowledgements

Equipment was provided by the Jesse D. Jones Analytical Laboratory at Murray State University (MSU). PtL ^β16Cl₂ elemental analysis was performed by George W. Kipphut at the Hancock Biological Station, MSU. VT XRD analysis was performed by the Rigaku^TM Corperation. Funding was provided by the MSU Committee on Institutional Studies and Research (CISR) and a Marshall and Annette Gordon Chemistry Research Grant. The authors are grateful for these contributions.