Banca de DEFESA: CLAUDIA ALLANA PEREIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : CLAUDIA ALLANA PEREIRA
DATE: 25/03/2026
TIME: 14:00
LOCAL: Videoconferência
TITLE:

Synthesis and study of the thermal, mesomorphic and photophysical Properties of new benzimidazole derivatives.

KEY WORDS:

Benzimidazole; Mesomorphic materials; Liquid crystals; Synthesis; Hydrogen bonding

PAGES: 95
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Orgânica
SPECIALTY: Síntese Orgânica
SUMMARY:

Organic compounds containing aromatic nitrogenous heterocyclic nuclei are of great interest in the field of liquid crystals (LCs) due to their electronic, thermal, optical, and electrochemical properties. The 2-phenyl-1H-benzimidazole nucleus is particularly interesting in the development of LCs, since it can combine versatility in terms of structural variation with amphoteric character to form layered networks, thus allowing the modulation of the properties of interest in the materials. This work presents the mesomorphic and thermal properties of a series of benzimidazole derivatives, aiming at a deeper understanding of the correlation between chemical structure and liquid-crystalline properties. The following compounds were synthesized: 2-(4-alkoxyphenyl)-1H-benzo[d]imidazole derivatives containing octyl (1a), decyl (1b), dodecyl (1c), and hexadecyl (1d) chains; and 2-(4-dodecyloxyphenyl)-1H-benzo[d]imidazo (2) and 5-(dodecyloxy)-2-(4-(dodecyloxy)phenyl)-1H-benzo[d]imidazo (3). All synthesized compounds exhibited liquid-crystalline behavior, with 1a, 1c, 1d, and 3 classified as enantiotropic, with different smetic mesophases; while 1b exhibits smetic and nematic mesophases in both phases. On the other hand, compound 2 presented itself as a monotropic CL, with a smetic mesophase. In general, no overall trend was observed in the temperatures at which the mesophases run as a function of the length of the alkyl chain between compounds 1a-d. The N-methyl derivative showed the lowest melting point and mesophase range, demonstrating the strength of the layer-packing induced by hydrogen bonds. Finally, compound 3, containing two dodecyl chains, showed the highest mesophase entry, melting, and degradation temperatures, because of Van der Waals interactions between the alkyl units. A photophysical study of compounds 1c, 2, and 3 was conducted, revealing poorly defined emission bands with moderate intensities and maximum emission wavelengths below 400 nm, independent of the solvent (dichloromethane, tetrahydrofuran, and isopropanol). Furthermore, increased emissions induced by aggregation and mild acidochromism were observed. Currently, other benzimidazole derivatives are being synthesized to broaden the scope for a better understanding of this class of compounds like liquid crystals, including ionic types. All target compounds, as well as the synthetic intermediates, were duly characterized using infrared spectroscopy (FTIR), 1H and 13C nuclear magnetic resonance (NMR), elemental analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TG), polarized light optical microscopy (POM), X-ray diffractometry (XRD), and computational studies to support the results. experimental.

COMMITTEE MEMBERS:
Externo à Instituição - EDUARD WESTPHAL - UFSC
Presidente - 1803692 - FABRICIO GAVA MENEZES
Externo à Instituição - RODRIGO CRISTIANO - UFPB
Interna - 3390839 - SENDY MELISSA SANTOS DO NASCIMENTO