Mesomorphic Metallo-Dendrimers Based on the Metal−Metal Bonded Ru₂(CO)₄ Sawhorse Unit

Dinuclear ruthenium complexes containing the stable metal−metal bonded Ru₂(CO)₄ sawhorse unit with two dendritic carboxylato bridges have been synthesized and characterized. All complexes Ru₂(CO)₄(O₂CR)₂L₂ (R = R¹, R², R³) containing cyanobiphenyl-based poly(arylester) dendrons of first (R¹), second (R²), and third (R³) generation and triphenylphosphine, pyridine, or 4-picoline ligands L proved to be mesomorphic, giving rise to smectic A or smectic A and nematic phases. The supramolecular organization within the smectic A phase is governed by the nature and structure of the mesogenic units and dendritic core. Such materials are of interest for the design of catalytically active anisotropic fluids.