Modulating Organic/Inorganic Segregation in Columnar Mesophases

This work reports an uncommon modulation of columnar segregation of metal–organic triphenylene liquid crystals by blending two structurally dissimilar metallomesogens that can self-associate through complementary electron donor–acceptor interactions. The constituent molecules are cis-[PtCl₂(CNR)₂] (CNR = 2-(6-(4-isocyanophenoxy)hexyloxy)-3,6,7,10,11-pentakisdodecyloxytriphenylene) that displays an organic/inorganic segregated columnar mesophase and [PtCl₂(Bipy)] (Bipy = didodecyl 2,2′-bipyridyl-4,4′-dicarboxylate) that shows a lamellar mesomorphism. The phase diagram of this system was constructed using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray scattering data. The phase diagram corresponds to a typical binary system with an intermediate compound (in this case a supramolecular aggregate) of stoichiometry [PtCl₂(CNR)₂]/2[PtCl₂(Bipy)], which is maintained in solution. This species shows an unusual columnar mesophase formed by the stacking of alternating organic/inorganic fragments. Quantum chemical calculations show that the columnar structure is mainly supported by complementary π electron donor–acceptor interactions between each triphenylene group of the isocyanide complex and a platinum-bipyridine molecule. This induces the elimination of the organic/inorganic columnar segregation of the isocyano parent component and constitutes an unconventional example of modulation of organic/inorganic segregation in columnar mesophases by the intercalation of metal complexes into hexaalkoxytriphenylene stacks.

Modulation of columnar segregation in metal−organic triphenylene liquid crystals is accomplished by blending two structurally dissimilar metallomesogens able to self-associate through complementary electron donor−acceptor interactions.