Dhiman Sukhvinder, Singh Ashutosh Sharan, Luxami Vijay, Kumar Gulshan
Department of Chemistry, MMEC, Maharishi Markandehswar (deemed to be University), Mullana, Haryana, 133207, India.
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
Phys Chem Chem Phys. 2025 Jul 17;27(28):14976-14984. doi: 10.1039/d5cp01412c.
The excited-state intramolecular proton transfer (ESIPT) dynamics of the ratiometric fluorescent benzimidazole-conjugated aminomalanitrile-based probe 1, an asymmetric structure synthesized by Gong ( 2019, , 30943-30951), were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) methods. The presence of strengthened dual-facet hydrogen bonds in the excited state, along with charge redistribution, facilitates the ESIPT process. The geometrical optimization of six conformations identified C3 and C4 as the most stable at S state (58.8% and 33.6%, respectively). Theoretical calculations align well with experimental absorption spectra and excitation values within the 350-425 nm range. FTIR analysis confirmed enhanced intramolecular hydrogen bonding (intraHBs) in C3 and C4, evidenced by redshifts and reduced interaction distances. The relative free energy profiles of tautomeric forms indicate stable states in S and S, with low energy barriers enabling proton transfer in the excited state. The vertical emission peaks closely match experimental spectra, underscoring the role of dual-facet hydrogen bonding in photophysical behaviour. The S-state potential barriers suggest an excited-state single proton transfer (ESPT) rather than a double proton transfer. Upon OCl addition, the ESIPT process remains uninhibited in probe 1, confirming its OCl sensing mechanism imidazole derivative formation. This study not only elucidates the ESIPT mechanisms of probe 1 but also enhances the understanding of HOCl detection, contributing to the development of novel fluorescent probes.
通过密度泛函理论（DFT）和含时密度泛函理论（TDDFT）方法，研究了比率型荧光苯并咪唑共轭氨基丙二腈基探针1（一种由龚在2019年合成的不对称结构，文献编号30943 - 30951）的激发态分子内质子转移（ESIPT）动力学。激发态中增强的双面对称氢键的存在，以及电荷重新分布，促进了ESIPT过程。对六种构象的几何优化确定C3和C4在S态时最稳定（分别为58.8%和33.6%）。理论计算与350 - 425 nm范围内的实验吸收光谱和激发值吻合良好。傅里叶变换红外光谱（FTIR）分析证实了C3和C4中分子内氢键（intraHBs）增强，表现为红移和相互作用距离减小。互变异构体形式的相对自由能分布表明在S态和S态存在稳定状态，低能垒使得激发态下质子能够转移。垂直发射峰与实验光谱紧密匹配，突出了双面对称氢键在光物理行为中的作用。S态势垒表明是激发态单质子转移（ESPT）而非双质子转移。加入OCl后，探针1中的ESIPT过程不受抑制，证实了其通过形成咪唑衍生物的OCl传感机制。本研究不仅阐明了探针1的ESIPT机制，还增进了对HOCl检测的理解，有助于新型荧光探针的开发。
