T-shaped monopyridazinotetrathiafulvalene-amino acid diad based chiral organogels with aggregation-induced fluorescence emission

A series of pyridazine coupled tetrathiafulvalene T-shaped derivatives with varying amino acid moieties have been synthesized and their gelation properties were studied in various organic solvents. Among these derivatives, two gelators bearing glycine or phenylalanine units display efficient gelation in aromatic and polar solvents. Interestingly, these gelators, except for the gelator containing two tryptophan units, are able to gel DMF via a solution-to-gel transformation when triggered with sonication for less than 20 s or cooled below zero. A number of experiments revealed that these gelator molecules self-assembled into elastically interpenetrating three-dimensional chiral fibrillar aggregates. Importantly, all of the resulting gels result in a dramatic enhancement of the fluorescence intensity compared with their hot solution in spite of the absence of a conventional fluorophore unit and the fluorescence was effectively quenched by the introduction of C60. Moreover, the gelators can be utilized for the removal of different types of toxic molecules, such as aromatic solvents and cationic dyes, from wastewater.

Boosting electrical conductivity in a gel-derived material by nanostructuring with trace carbon nanotubes

An organogelator with two distinct π-functional units is able to incorporate carbon nanotubes into its mesh of fibres in the gel state. The morphology of the material derived from this nanocomposite after evaporation of the solvent is a complex mesh of fibres which is clearly different from the pure gelator. This feature indicates a role of the nanotubes in assisting the formation of a fibre structure in the gel thanks to their interaction with the pyrene units in the organogelator. The nanocomposite conducts electricity once the p-type gelator is doped with iodine vapour. The change in morphology caused by the carbon material increases the conductivity of the material compared with the purely organic conducting system. It is remarkable that this improvement in the physical property is caused by an extremely small proportion of the carbon material (only present at a ratio of 0.1% w/w). The practically unique properties of TTF unit allow measurements with both doped and undoped materials with conducting atomic force microscopy which have demonstrated that the carbon nanotubes are not directly responsible for the increased conductivity.

Organogelators based on TTF supramolecular assemblies: synthesis, characterization, and conductive property

A closely related family of organogelators 1-2 appended one or two electroactive tetrathiafulvalene (TTF) residues, has been designed and readily synthesized by Sonogashira reactions. These compounds can gelate a variety of organic solvents in view of multiple intermolecular interactions, and compounds 2 with two TTF subunits exhibit higher gelation ability than their corresponding 1. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigation of the xerogels from toluene gave a visual image showing that fibrillar aggregates are entangled in three-dimensional network structures. The columnar TTF cores stacking in the fiber, evidenced by the mixed-valence states absorption at around 2000 nm in ultraviolet-visible-near-infrared (UV-vis-NIR) spectra, provide an efficient pathway for the electron conduction. Upon oxidized by iodine, these xerogels exhibit semiconductive behaviors with moderate levels of conductivity. Additionally, the electrical conductivity of doped-xerogels 2 is 1 order of magnitude higher than that of 1 under identical conditions.