Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China.
Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2023 Nov 5;300:122937. doi: 10.1016/j.saa.2023.122937. Epub 2023 May 30.
The compound in solvents with triple fluorescence feature of excited state intramolecular proton transfer (ESIPT) has a broad prospect in fluorescent probes, dye sensors and molecular synthesis of photosensitive dyes. An ESIPT molecule hydroxy-bis-2,5-disubstituted-1,3,4-oxadiazoles (compound 1a) emits two fluorescence peaks in dichloromethane (DCM) and three fluorescence peaks in dimethyl sulfoxide (DMSO). [Dyes and Pigments 197 (2022) 109927]. Two longer peaks were attributed to enol and keto emission in both solvents and the shortest third peak in DMSO was just attributed simply. However, there is a significant difference in proton affinity between DCM and DMSO solvents which has influence on the position of emission peaks. Therefore, the correctness of this conclusion needs to be further verified. In this research, density functional theory and time-dependent density functional theory method are used to explore ESIPT process. Optimized structures indicate ESIPT occurs through molecular bridge assisted by DMSO. The calculated fluorescence spectra demonstrate two peaks indeed originated from enol and keto in DCM, while interestingly three peaks are originated from enol, keto and intermediate in DMSO. Infrared spectrum, electrostatic potential and potential energy curves further prove existence of three structures. We reveal the mechanisms that compound 1a molecule occurs ESIPT in DCM solvent and undergoes an ESIPT through assisted by DMSO molecular bridge. Additionally, three fluorescence peaks in DMSO are reattributed. Our work is expected to provide an insight for understanding intra- and intermolecular interactions and synthesis of efficient organic lighting-emitting molecule.
具有激发态分子内质子转移（ESIPT）三重荧光特性的溶剂中的化合物在荧光探针、染料传感器和光致变色染料的分子合成方面具有广阔的前景。ESIPT 分子羟基双-2,5-二取代-1,3,4-噁二唑（化合物 1a）在二氯甲烷（DCM）中发射两个荧光峰，在二甲基亚砜（DMSO）中发射三个荧光峰。[染料和颜料 197（2022）109927]。两个较长的峰归因于两种溶剂中烯醇和酮的发射，而在 DMSO 中最短的第三个峰则归因于简单的酮。然而，DCM 和 DMSO 溶剂之间的质子亲和力存在显著差异，这会影响发射峰的位置。因此，需要进一步验证该结论的正确性。在这项研究中，使用密度泛函理论和含时密度泛函理论方法来探索 ESIPT 过程。优化结构表明，ESIPT 通过 DMSO 分子桥辅助发生。计算的荧光光谱表明，在 DCM 中，两个峰确实源自烯醇和酮，而有趣的是，在 DMSO 中三个峰源自烯醇、酮和中间产物。红外光谱、静电势和势能曲线进一步证明了三种结构的存在。我们揭示了化合物 1a 分子在 DCM 溶剂中发生 ESIPT 并通过 DMSO 分子桥辅助发生 ESIPT 的机制。此外，对 DMSO 中三个荧光峰进行了重新归因。我们的工作有望为理解分子内和分子间相互作用以及高效有机发光分子的合成提供深入了解。
