Chain-Length- and Concentration-Dependent Isomerization of Bithiophenyl-Based Diaminotriazine Derivatives in Two-Dimensional Polymorphic Self-Assembly^§

Abstract

n = 10,12,16,and 18) with different chain lengths display colhex/p6mm mesophases. Their supramolecular selfassembled mechanism is investigated using scanning tunneling microscopy (STM) at the 1-octanoic acid/graphite interface at various concentrations. The chain length effect on the twodimensional adlayers is observed in this system, and 2TDT-n molecules show a structural phase transition from the four-leaf arrangement to the two-row linear nanostructure accompanied by the emergence of molecular isomerization with the increase of the side-chain length. The self-assembled structure of 2TDT-10 is composed of a four-leaf pattern with uniform s-cis conformers. In 2TDT-12, three kinds of nanostructures (bamboo-like, two-row linear pattern-I, and flower-like) are observed. These nanostructures are randomly constituted by cis and trans conformers, and the ratios of the s-cis conformer in three kinds of patterns are 55.7, 42.3, and 62.5%, respectively. Furthermore, when n = 16 and 18, the ratio of the s-cis conformer further decreases to 19.0 and 4.3%, respectively. Those molecules mainly form linear nanostructures consisting of s-trans conformers. Therefore, it is reasonable to conclude that the side-chain length has a great effect on the selfassembled patterns and the molecular conformation of bithiophenyl-based diaminotriazine derivatives. Density functional theory calculations are applied to optimize molecular conformers and assess their single-point energies, showing that the s-cis conformation has higher energy than the s-trans conformer. We speculate that the ratio of two conformers in nanostructures might be similar to that of the liquid crystalline phase.

Solvent Effects Used for Optimal Simultaneous Analysis of Amino Acids via 19F NMR Spectroscopy

“…This demonstrates that thermally stable trans isomer tends to allosterically transform to cis isomer that is kinetically stable conformation. Nevertheless, 19 F resonance signals of 100 mM 2FBA-modified AAs still broadened at a range of 328∼333 K, implying the concentration-dependent isomerization of Schiff base cis – trans and its lower rate of conformational isomerization at a higher concentration. , It might require a higher temperature. Thus, the aggregation would not occur in the NMR solution at 298 K. Hereof, we propose that the difference of chemical shifts was caused by the changes in viscosity of various concentrations of NMR solutions and potential ion pairing.…”

Surface supramolecular assemblies tailored by chemical/physical and synergistic stimuli: a scanning tunneling microscopy study

“…(d) Bithiophenylbased diaminotriazine derivatives, reproduced with permission. 55 Copyright 2022, American Chemical Society. (e) 1,3,5-Tris(4-carboxyphenylethynyl)-2,4,6-trimethylbenzene (BT r B) and 1,3,5-tri(4-carboxyphenyl)benzene (BTB), reproduced with permission.…”

“…The chain length of molecules along with different concentrations of solvents can add a synergistic effect to alteration of the final self-assembled structure. [120][121][122] Wang et al 55 demonstrated the formation of colhex/p6mm mesophases from a series of liquid crystal materials of bithiophenyl-based diaminotriazine derivatives (2TDT-n) with varying chain lengths (n = 10, 12, 16, and 18). When these molecules form 2D assemblies on the HOPG surface, they contain cis and trans conformations randomly.…”

Diagnosis of doped conjugated polymer films using hyperspectral imaging

“…12–15 Among various conjugated polymer families, polythiophene derivatives show the most promising optical and electrical characteristics where the electrical conductivity is significantly improved through structural modifications, doping strategies, and by controlling the microstructure through process optimization. 16–21…”

“…[12][13][14][15] Among various conjugated polymer families, polythiophene derivatives show the most promising optical and electrical characteristics where the electrical conductivity is signicantly improved through structural modications, doping strategies, and by controlling the microstructure through process optimization. [16][17][18][19][20][21] The electrical conductivity of the most commonly used poly(3-hexylthiophene-2,5-diyl) (P3HT) doped with 2,3,5,6-tetrauoro-7,7,8,8-tetracyanoquinodimethane (F 4 TCNQ) is around 10 S cm −1 , 22 which increases to 100 S cm −1 when the P3HT structure is modied with ethylene glycol side chains. 23 Another prototypical conjugated polymer poly(bisdodecylquaterthiophene) (PQT) shows the highest electrical conductivity of 350 S cm −1 aer introducing sulphur atoms into side chains and upon doping with NOBF 4 .…”