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)···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 (PtLnCl4, 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 PtL1Cl2·CH2Cl2, PtL2Cl2, and PtL16Cl2·•2CHCl3. 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.