Mesomorphic Behavior of Symmetric Azomethine Dimers Containing Different Chromophore Groups

Abstract

A series of new azomethine dimers was synthesized by the condensation reaction of flexible bis-benzaldehydes with four aromatic amines containing phenyl, naphthyl, anthracene and pyrene groups. Their right structure was confirmed by FTIR and 1H-NMR spectroscopy and their thermal properties were investigated by thermogravimetric analysis, differential scanning calorimetry and polarized light optical microscopy. A view on their photophysical behavior was gained by UV-vis and photoluminescence spectroscopy. The dimers containing pyrene and anthracene presented liquid crystalline behavior, while the other dimers were crystalline compounds. Two dimers containing pyrene moieties formed mesomorphic glasses and had intense luminescence, promising properties for applications in building optoelectronic devices.

Differential insights into structural dynamics and photophysical behavior of two phosphorus-containing diesters

“…The most intensely studied liquid crystals are calamitic ones, which generally contain a rigid core, flexible chains, and linkage units such as ester, ether, azo, and azomethine. [15][16][17][18][19][20] The ester linkage unit is widely used in liquid crystals due to its stability and easy synthesis pathways. On the other hand, the reversible direction of the polar ester linking group influences the polarizability of the molecule and gives rise to significant changes in thermotropic behavior.…”

Pyrene-Fused Poly-Aromatic Regioisomers: Synthesis, Columnar Mesomorphism, and Optical Properties

“…Due to its natural pseudo-circular shape, pyrene is intrinsically conducive to the formation of discotic systems, but its insertion within calamitic or bent structures has not been detrimental to mesomorphism induction. At first, 1-functionalized pyrene was reported to produce dimeric liquid crystals, symmetrical and non-symmetrical, and to yield essentially nematic (also including the so-called twist–bend nematic) and smectic phases [ 22 , 23 , 24 , 25 ]. Pyrene was also inserted in cyclophanes (via 1,6-positions), i.e., pyrenophanes, also yielding a nematic phase [ 26 , 27 , 28 ], as well as in polycatenars [ 29 ] and, recently, in some bent-core mesogens [ 30 ], for which columnar mesophases were systematically induced.…”

UV light sensing and switching applications of dimeric smectic liquid crystals: comparative calculations

“…Structural design and practicality are crucial facets in the engineering of LC molecules for managing the physical properties and constancy of mesophases [ 4 ]. The preliminary awareness of LC dimers [ 5 – 7 ] arose from their prospective use as model molecules that help in the understanding of complex polymeric systems. However, these dimers attained noteworthy attention as they exhibit fairly dissimilar behaviour to usual small molar mass LCs.…”