Multifunctional Supramolecular Dendrimers with an s‐Triazine Ring as the Central Core: Liquid Crystalline, Fluorescence and Photoconductive Properties

Abstract

Novel liquid crystal (LC) dendrimers have been synthesised by hydrogen bonding between an s‐triazine as the central core and three peripheral dendrons derived from bis(hydroxymethyl)propionic acid. Symmetric acid dendrons bearing achiral promesogenic units have been synthesised to obtain 3:1 complexes with triazine that exhibit LC properties. Asymmetric dendrons that combine the achiral promesogenic unit and an active moiety derived from coumarin or pyrene structures have been synthesised in order to obtain dendrimers with photophysical and electrochemical properties. The formation of the complexes was confirmed by IR and NMR spectroscopy data. The liquid crystalline properties were investigated by differential scanning calorimetry, polarising optical microscopy and X‐ray diffractometry. All complexes displayed mesogenic properties, which were smectic in the case of symmetric dendrons and their complexes and nematic in the case of asymmetric dendrons and their dendrimers. A supramolecular model for the lamellar mesophase, based mainly on X‐ray diffraction studies, is proposed. The electrochemical behaviour of dendritic complexes was investigated by cyclic voltammetry. The UV/Vis absorption and emission properties of the compounds and the photoconductive properties of the dendrons and dendrimers were also investigated

Supramolecular liquid crystalline dendrimers with a porphyrin core and functional carboxylic acid dendrons

“…The largest shis in the dendron part are related to the nuclei nearest to the H bonds, as discussed in a previous publication. 19 Thus, the shi and the change in the shape of the diastereotopic methylene (H S , see Scheme 1) signals aer H-bonding are particularly marked: H S protons are deshielding 0.08 ppm in both complexes with regard to acid Ac-G1A2, and the methyl H U signal are also deshielding (see Fig. 1).…”

“…17 We recently studied a new type of liquid crystal dendrimers functionalised with carbazole, coumarin and pyrene groups as uorescence moieties. 18,19 These compounds were prepared by hydrogen bonding between a triazine core (M), as an electrontransporting unit, and three peripheral carboxylic acid bifunctionalised dendrons derived from bis(hydroxymethyl)propionic acid (bis-MPA).…”

“…As a continuation of our research programme in this area, we synthesised and characterised three novel families of compounds that were formed by hydrogen bonding between 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP) or zinc metalated porphyrin (ZnTPyP) as the core and four peripheral bifunctionalised dendrons derived from bis(hydroxymethyl)propionic acid (bis-MPA), which were described in a previous paper. 19 The TPyP unit was selected for this work due to its ability to recognise other molecules through the donation and acceptance of hydrogen bonds, 20,21 a characteristic that plays a key role in the self-organisation of molecules and thus facilitates the formation of liquid crystals in low molecular weight compounds as well as in polymers or dendrimers. Zinc complexes of porphyrin dendrimers have been prepared with the aim of increasing the stability and providing better photophysical properties compared to free-base porphyrins.…”

“…Pyrene is a widely ester group, and the appropriate promesogenic acid by previously reported method. 19 Typical procedure for the synthesis of the dendrimers derived from porphyrins and metalloporphyrins…”

New Ionic bis‐MPA and PAMAM Dendrimers: A Study of Their Biocompatibility and DNA‐Complexation

“…This via allows the preparation of the dendrimers by a self‐assembly process based on non‐covalent interactions . Thus, dendrimeric structures based on metal coordination chemistry, hydrogen‐bonding interactions, or electrostatic interactions have been described.…”