Most triazine-based liquid crystalline (LC) dendrimers reported thus far are the main-chain LC macromolecules with long flexible chains at their periphery and attached to internal rigid or semi-rigid frameworks. Their formation of mesogenic phases often depends on the intermolecular face-to-face π–π interactions between dendritic molecules, which are unusual. Their mesogenic phases can also be formed by incorporation of mesogenic units to the dendritic skeletons through long flexible chains, as most side-chain LC dendrimers, in which the peripheral mesogenic units generally play the important roles. For main-chain triazine-based dendrimers, their morphology is maintained by restricted freedom of rigid or semi-rigid connecting units, and their formations of LC phases are therefore not straightforward to be controlled. In this review, we thus describe modulating of the intermolecular face-to-face π–π interactions between the triazine-based dendritic molecules, with the aim of forming LC phases through molecular design.

Reaction of tert-butyl 3,5-diaminobenzoate with cyanuric chloride gave triazine-based macrocycle 1 in 44.3% yield, which was characterized by 1 H and 13 C NMR spectroscopy, mass spectrometry, and elemental analysis. A thermally stable HOF-1 from macrocycle 1 was crystallized from hexane−THF, and its porous property was studied. The crystallographic analysis revealed that the void space was maintained by the π−π, H-bond, and C−H−π interactions between the aromatic moieties in a solid state. The framework changes while losing solvents and produces various emission intensities when irradiated. After completely removing the solvents, the void space of HOF 1 was still available for solvation, and surprisingly, the framework almost recovered after adsorbing solvents according to the powder-XRD study.

Two triazine-based dendrimers with peripheral 1,3,5-triamidobenzene (1-3-5-TAB) functionality were prepared, and their void spaces in the bulk solid were investigated. We examined dendrimers of three core lengths and determined the one with the longest core exhibits the largest void space because the peripheral amides were not imbedded in the internal space of each dendritic molecule. The new dendrimers as solids were observed to adsorb volatile organic chemicals efficiently. Importantly, because the dendrimers are soluble in organic solvents, the adsorbed VOCs can be quantified by 1H-NMR spectroscopy by choosing a chemical shift (δ) of dendrimers as the internal standard to exclude interfering impurity signals, a much simpler and more efficient protocol than the traditional GC technique for the VOC quantification. One dendrimer was found to adsorb 24 equivalents of pyridine, so its adsorption capacity is equivalent to 946.2 mg/g. This is a more than 2-fold increase than the reported values by other porous materials.

A dendrimer with 3-fold symmetry and piperazinoamido moieties was prepared in ~35% yield. This molecule was observed to exhibit columnar phases on thermal treatment and possess free void space in...

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