N,N-二甲基-6-丙酰-2-萘胺氢键复合物激发态超快动力学研究

Ultrafast Excited State Dynamics Investigation of N,N-dimethyl-6-propionyl-2-naphthylamine Hydrogen-bonded Complexes

抑制扭转分子内电荷转移(TICT)的形成能够显著增强发光材料的荧光强度和光稳定性,然而,目前缺乏准确预测TICT存在的方法。本文基于Kamlet-Taft理论,通过稳态/瞬态吸收光谱结合量化计算,对N,N-二甲基-6-丙酰-2-萘胺(PRODAN)在不同溶剂中的激发态动力学进行了研究。稳态光谱表明,PRODAN氢键复合物的斯托克斯红移主要依赖溶剂极性和供氢能力。瞬态吸收光谱表明,快时间τ_(1)和τ_(2)归属为分子内电荷转移和TICT形成过程,而慢时间τ_(3)和τ_(4)归属为溶剂化和荧光辐射过程。此外,结果表明极性和供氢能力的增大会加快PRODAN氢键复合物的动力学过程。计算表明,在较高极性且强供氢能力的甲醇溶剂中能形成稳定的TICT态。研究结果为荧光探针分子结构设计和溶剂选择提供了一定的指导意义。

Suppressing the formation of twisted intramolecular charge transfer(TICT)can markedly improve the fluorescence intensity and photostability of luminescent materials.However,accurate methods for predicting the presence of TICT are currently lacking.This paper investigated the excited state dynamics of N,N-dimethyl-6-propionyl-2-naphthylamine(PRODAN)across various solvents utilized the Kamlet-Taft theory,coupled with both steady-state and transient absorption spectroscopy,complemented by quantitative calculations.The analysis of steady-state spectra revealed that the primary determinant of the Stokes redshift in the PRODAN complexes is the solvent's polarity and hydrogen-donating capacity.Transient absorption spectra provided insights into fast timescales(τ_(1) and τ_(2)),corresponding to the formation of intramolecular charge transfer and TICT processes,while slower timescales(τ_(3) and τ_(4))were associated with solvation and fluorescence radiation processes.Furthermore,experimental findings demonstrated that an increase in solvent polarity and hydrogen-donating ability expeditiously influences the dynamics processes within PRODAN hydrogen-bonded complexes.Theoretical computations solidified these observations,confirming the formation of a stable TICT state in highly polar and strongly hydrogen-donating methanol solvent.These insights not only contribute to our understanding of the ultrafast dynamics of PRODAN but also provide valuable guidance for the strategic design of fluorescent probe molecules and thoughtful solvent selection in the field of fluorescence research.