Columnar Mesophases with 3D Order from New Functional Nonconventional Star‐Shaped Mesogens

Abstract

Star‐shaped oligobenzoates with naphthalene chromophores assemble in columnar mesophases. In the low‐temperature phases, mesogens self‐organize helically along the columns, leading to columnar liquid crystal phases with 3D order (see image). The formation of these structures is driven by optimization of space‐filling and nanosegregation. Naphthalene chromophores are segregated in the center of the columns and operate as hopping sites for charges.

Star Mesogens (Hekates)—Tailor‐Made Molecules for Programming Supramolecular Functionality

“…Recently, star-shaped oligobenzoates have been equipped with naphthalene chromophores (1 j, Figure 10), which are known to promote fast charge carrier mobility. [35] In the highly ordered 3D helical columnar phase the naphthalene chromophores aggregate in the confined space at the centre of the column, as evidenced by UV/Vis and fluorescence spectroscopy. This is a promising supramolecular structure to test the charge carrier mobility with the microwave conductivity techniques (PR-TMRC).…”

“…As an example, the synthesis of oligobenzoate scaffolds including a functional naphthalene unit is detailed in Scheme 3. [35] The oligobenzoate synthesis is performed with a benzylprotecting-group strategy. It starts with the peripheral building block 7 a (n = 0) and the choice of the number and type of flexible chains.…”

“…For the latter, the supramolecular chiral environment of the naphthalene chromophores, and thus, the helical stacking in the low-temperature orthorhombic phase, was confirmed by CD spectroscopy. [35] Oligobenzoate Hekates with three different arms can be divided in three principal classes, according to the parameters of diversity: 1) Hekates with three arms of different lengths, 2) Hekates with three arms possessing incompatible peripheral chains [60] and 3) Hekates with various different repeating units in the oligobenzoate scaffold. Of course, it is possible to vary all three of these parameters in order to tailor specific structures and properties.…”

“…Figure 10. Semi-flexible [35] (1 j) and flexible [37] (16) Hekates with small chromophores revealing high PR-TRMC charge carrier mobilities in ordered columnar mesophases: Col bsorh base-centred orthorhombic columnar and Col hp hexagonal columnar plastic mesophase. [59] www.chemeurj.org When this strategy was refined with three triphenylenes linked to a benzene-1,3,5-triscarboxA C H T U N G T R E N N U N G amide (16; Figure 10), hydrogen bonding resulted in a supercolumnar structure with the highest charge carrier mobility observed for triphenylene derivatives.…”

Trimesic Acid-Based Star Mesogens with Flexible Spacer: Synthesis and Mesophase Characterization

“…The design of hekates is achieved by introducing rod-like arms either directly or through a flexible spacer. The remarkable feature of these mesogens is the change of molecular shape driven by self organisation [23] when changing the temperature. Thus, investigations of such an important class of mesogens would provide more insights into the relationship between structure and mesophase formation and this will be useful to exploit the star mesogens for new applications.…”