Mesogenic [Rh(L)4](A) complexes form mesophases with RhI⋯RhI-containing and triphenylene-discotic segregated columns. Effect of RhI⋯RhI interactions and A− = [Au(CN)2]− on hole mobility

Abstract

Rh^I complexes [Rh(L)₄](A) (A⁻ = Cl⁻, BF₄⁻, [Au(CN)₂]⁻) with conventional arylisocyanides (p-MeC₆H₄(NC), L^A; p-MeOC₆H₄(NC), L^B; 3,5-(OMe)₂C₆H₃(NC), L^C) or with the alkoxy-functionalized triphenylene-arylisocyanides TPh(OC₁₂H₂₅)₅(O(CH₂)₆OC₆H₄(NC)-p) (L^D1) and TPh(OC₁₂H₂₅)₅(O(CH₂)₆OC₆H₂Me₂(NC)-p) (L^D2), have been prepared and their self-assembly, aggregation, optical, redox, mesogenic and conducting properties investigated. Intermolecular π–π stacking, Rh^I⋯Rh^I, and Rh^I⋯Au^I interactions rule the crystal packing and aggregation in solution for the complexes with L^A, L^B, and L^C. For the Rh^I complexes with the alkoxy-functionalized-triphenylene isocyanides L^D1 and L^D2 mesogenic behaviour is induced, giving rise to multicolumnar mesophases in broad temperature ranges (ca. 70–160 °C). Detailed analysis (POM, DSC, SAXS/WAXS and GIWAXS) of the columnar mesophases has allowed us to propose precise packing models that explain the diverse supramolecular arrangements found in the nanostructured condensed phases. Columnar alignments predominantly with Rh⋯Rh interactions (or Rh⋯Au, only for L^D2 in specific conditions) are observed, depending on the aligning conditions. The hole mobility in the columnar mesophases of the complexes with Rh⋯Rh interactions are ∼1 cm² V⁻¹ s⁻¹, that is up to four orders of magnitude higher than those reported for columnar mesophases of organic triphenylene derivatives, and increases one order of magnitude further in the mesophases containing the [Au(CN)₂]⁻ counteranion.