da Silva Simões Simone, Oliveira Mário Sérgio Silva, Longo Ricardo Luiz, Falcão Eduardo Henrique Lago
Departamento de Química Fundamental, Universidade Federal de Pernambuco, Recife, 50740- 540, Pernambuco, Brazil.
Programa de Pós-Graduação em Química, Universidade Federal de Pernambuco, Recife, 50740- 540, Pernambuco, Brazil.
J Fluoresc. 2025 Aug 25. doi: 10.1007/s10895-025-04504-7.
The photophysical properties of two pyridyl isomers of 1,3,4-oxadiazole, namely 2-(4-(dodecyloxy)phenyl)-5-(pyridin-3-yl)-1,3,4-oxadiazole (Oxa3py) and 2-(4-(dodecyloxy)phenyl)-5-(pyridin-4-yl)-1,3,4-oxadiazole (Oxa4py), were systematically investigated to elucidate the impact of molecular structure and different solvent environments on the ground and excited states. The effect of the pyridinic nitrogen position was evaluated in terms of solvatochromism, charge transfer properties, and aggregation behavior in methanol-water mixtures. Both compounds exhibit positive solvatochromism, showing a considerable bathochromic shift of 45 nm for Oxa3py and 66 nm for Oxa4py in their emission spectra obtained in carbon tetrachloride and dimethyl sulfoxide. The McRae-Bayliss model and the empirical Reichardt solvent polarity scale, E(30), indicate that dipolar effects govern this behavior. The compounds formed aggregates in methanol-water mixtures, displaying a pronounced hypsochromic shift and a distinct influence on emission intensities. Time-dependent density functional theory (TD-DFT) calculations combined with natural transition orbitals (NTOs) analysis confirm the occurrence of intramolecular charge transfer from the dodecyloxyphenyl group to the pyridyl moiety. These findings provide fundamental insight into structure-property relationships and demonstrate how environmental factors and molecular architecture jointly modulate photophysical behavior. This knowledge contributes to the rational design of new optoelectronic materials based on simple heteroaromatic scaffolds.
系统研究了1,3,4-恶二唑的两种吡啶基异构体，即2-(4-(十二烷氧基)phenyl)-5-(吡啶-3-基)-1,3,4-恶二唑（Oxa3py）和2-(4-(十二烷氧基)phenyl)-5-(吡啶-4-基)-1,3,4-恶二唑（Oxa4py）的光物理性质，以阐明分子结构和不同溶剂环境对基态和激发态的影响。从溶剂化显色、电荷转移性质以及在甲醇-水混合物中的聚集行为方面评估了吡啶氮位置的影响。两种化合物均表现出正溶剂化显色，在四氯化碳和二甲亚砜中获得的发射光谱中，Oxa3py有45nm的显著红移，Oxa4py有66nm的显著红移。McRae-Bayliss模型和经验性的Reichardt溶剂极性标度E(30)表明，偶极效应决定了这种行为。这些化合物在甲醇-水混合物中形成聚集体，表现出明显的蓝移以及对发射强度的显著影响。含时密度泛函理论（TD-DFT）计算结合自然过渡轨道（NTOs）分析证实了从十二烷氧基苯基到吡啶基部分发生了分子内电荷转移。这些发现为结构-性质关系提供了基本见解，并展示了环境因素和分子结构如何共同调节光物理行为。这一知识有助于基于简单杂芳基支架合理设计新型光电子材料。
