Recent advances in heterocycle-based metal-free calamitics

Abstract

The role of heterocycle-based calamitic liquid crystals has been investigated as potential candidates for photo-physical and opto-electronic applications.

Recent synthetic advances in pyridine-based thermotropic mesogens

“…It is interesting to note that the design and development of various heterocyclic-based thermotropic liquid crystals has gained the interest of researchers due to the stress-free modi-cation of molecular shapes and their excellent ability to impart lateral and/or longitudinal dipoles. [1][2][3] In fact, these features have helped further several photochemical and optical applications in areas of material science, such as organic photovoltaic devices, [4][5][6] optical signal processing and storage, 7 switching ferroelectric materials, 8 and organic transistors. 9 In the last few years, a pronounced number of thermotropic liquid crystalline materials with core moieties comprising heterocyclic rings have been designed, synthesized and characterized.…”

“…These heterocyclic rings consist of electronegative hetero-atoms (such as nitrogen, oxygen, and sulphur), and the occupancy of these electronegative atoms frequently triggers diminished symmetry of the complete molecule and, thereby, develops powerful polar induction. 7 Highly p-conjugated mesogens bearing heterocycles are showing enhanced use in organic photonics. 10 In fact, vemembered N-heterocyclic compounds are frequently fabricated in materials science due to their ability to further interact (or hydrogen bond) with metal atoms.…”

“…10 In fact, vemembered N-heterocyclic compounds are frequently fabricated in materials science due to their ability to further interact (or hydrogen bond) with metal atoms. 7 Five-membered Nheterocyclic compounds are capable of building complexes with metals or may exhibit mesogenic natures through hydrogen bond donor-acceptor assemblies via specic interactions. Also, some of these compounds can be electron rich or decient based on the ring nature and, therefore, can be utilized in organic electronic applications.…”

“…In this context, pyrazoles have been efficiently implemented in the domain of metallo-mesogens; at the same time, triazoles have been utilized to produce supramolecular mesogens. 7 The use of six-membered N-heterocyclic systems in mesogenic molecules moderately alters their molecular geometry in contrast with their benzene analogs. However, the site of the Nheteroatom has a signicant impact on the dispersion forces, the dipole moment, the polarizability of the molecule and, inevitably, on the dielectric nature of the mesogen.…”

New Type of Columnar Liquid Crystal Superlattice in Double‐Taper Ionic Minidendrons

“…Columnar liquid crystal phases,h aving 2D positional order, have come al ong way since their first discovery in 1977 in discotic molecules. [1] Subsequent years have seen columnarmesogens increasing in complexity andv ariety of shapes (star, [2,3] bent core, [4] bowl, [5,6] helicene, [7] heterocycle, [8] T-and Xshape) [9] and typeso fn on-bonded interactions (H-bonding, [10] donor-acceptor, [11] ionic, [12] coordination). [13] Wedge-shapedm olecules that consist of at least two moderately incompatible parts often exhibit liquid crystal (LC) phases with 2D or 3D periodicity.T ypical compounds of this type are dendrons and "mini-dendrons" (first-generation wedge-shaped dendrons) containing an aromatic core and af unctional group at the narrow end, and flexible terminal alkyl or oligo(ethylene oxide) chains at the wide end.…”