Effect of Axial Interactions on the Formation of Mesophases: Comparison of the Phase Behavior of Dialkyl 2,2′-bipyridyl-4,4′-dicarboxylate Complexes of Pt(II), Pt(IV), and Pt(II)/Pt(IV) Molecular Alloys

Crystal engineering through the use of metal-based interactions is relatively common, but this approach has not been widely used to develop highly ordered liquid-crystalline (LC) phases. Herein is presented a Pt(II)/Pt(IV) system with a highly ordered LC phase engineered to form through metal-based MX chain interactions of the type Pt(II)center dot center dot center dot Cl-Pt(IV). This LC material constitutes a molecular alloy in which a single mesophase is formed from two components, and is the first alloy to include a Pt(IV) component. The molecular alloy was characterized via differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and variable-temperature X-ray diffraction (VT XRD). The alloy properties are contrasted with complimentary analyses of the individual components. The newly synthesized tetrachloro(dialkyl 4,4'-dicarboxylate-2,2'-bipyridyl)platinum(IV) complexes ((PtLCl4)-Cl-n, n is the number of carbons in the alkyl chain) are themselves liquid crystalline. Structural and thermal properties of the Pt(II) analogues are presented to provide context to the behaviors of the Pt(IV) species and the alloys. Single-crystal X-ray diffraction data is presented for (PtLCl2)-Cl-1 center dot CH2Cl2, (PtLCl2)-Cl-2, and (PtLCl2)-Cl-16-center dot 2CHCl(3). This study demonstrates the potential of mesophase ordering through carefully engineered metal-based interactions. The resulting alloy provides a phase for studying MX chain interactions outside of the solid state.