Inspecting the Electronic Architecture and Semiconducting Properties of a Rosette‐Like Supramolecular Columnar Liquid Crystal

Abstract

Computational and experimental studies unravel the structural and electronic properties of a novel supramolecular liquid crystal built through a hierarchical assembly process resulting in an H‐bonded melamine rosette decorated with peripheral triphenylenes. The six‐fold symmetry of the mesogen facilitates the formation of a highly organized hexagonal columnar mesophase stable at room temperature. X‐ray diffraction and electron density maps confirm additional intra‐ and intercolumn segregation of functional subunits, and this paves the way for 1D charge transport. Indeed, hole mobility has been measured and found to be higher than for related mesogens. DFT calculations of HOMO and LUMO levels and parameters such as reorganization energy and transfer integral of the rosette structure have been achieved, and not only validate the columnar organization but also establish the way it translates into a favorable electronic architecture and molecular orbital interactions to promote charge carrier mobility.

Charge Mobility in Discotic Liquid Crystals

“…Beyond the flat core/flexible periphery paradigm, columnar phases can be obtained using a variety of other molecular architectures [54], such as conical cores [55,56], macrocycles [57][58][59] or metallomesogens [60,61]. In addition, the disk-shaped unit may not necessarily be a single entity of covalently linked atoms: in the recent literature there are in fact numerous examples of columnar phases formed by "supramolecular" disk-shaped units, where different dendrons assemble under driving forces tied to molecular shape and/or hydrogen bonds, dipolar or other specific interactions [62][63][64]. Figure 5 shows some examples of these molecular architectures and assemblies.…”

Triphenylamine- and triazine-containing hydrogen bonded complexes: liquid crystalline supramolecular semiconductors

“…Such a possibility provides an efficient bottom-up methodology to attain hierarchically organized supramolecular materials based on LCs, [37][38][39] and yield successfully supramolecular semiconductors. 40,41 In order to prepare TPA-containing semiconductors we designed a hydrogen bonded complex formed by two complementary units, a star-shaped triazine, T3C 4 (blue in Fig. 1), and three benzoic acid derivatives bearing the TPA unit, A-2BnOC 12 -TPAnC 12 (n = 2, 4, 6), (Fig.…”

Self-assembled discotics as molecular semiconductors

“…121–123 The H-bonded approach has also been applied in melamine cores to design rosette-like columnar structures where the segregated mesophase assembly gave a hole mobility of 4 × 10 −2 cm 2 V −1 s −1 , but electron mobility could not be obtained. 124 H-Bonded DLCs based on triazine and tris(triazolyl)triazine have also been reported. 125,126…”

“…[121][122][123] The H-bonded approach has also been applied in melamine cores to design rosette-like columnar structures where the segregated mesophase assembly gave a hole mobility of 4 Â 10 À2 cm 2 V À1 s À1 , but electron mobility could not be obtained. 124 H-Bonded DLCs based on triazine and tris(triazolyl)triazine have also been reported. 125,126 Motivated by all these examples of coaxial nano-segregation and their impact on ambipolar charge transport, our group took a 1 : 3 supramolecular complexation approach through hydrogen-bonding between an electron-deficient heptazine core and electron-rich triphenylene acid units to synthesize the DLC HPz-TP (Fig.…”