Ultrafast Dynamics of a Solvatochromic Dye, Phenol Blue: Tautomerization and Coherent Wavepacket Oscillations
Ultrafast Dynamics of a Solvatochromic Dye, Phenol Blue: Tautomerization and Coherent Wavepacket Oscillations
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溶剂变色染料酚蓝的超快动力学：互变异构和相干波包振荡
DOI：
10.1021/acs.jpcb.1c07501
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Nagasawa Yutaka
中科院分区：
文献类型：
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作者：
Ota Chikashi;Matsumoto Akifumi;Hidaka Tsubasa;Sugihara Keita;Teramoto Takahiro;Nagasawa Yutaka
飞秒时间分辨瞬态吸收光谱进行了非荧光溶剂化显色染料，酚蓝，N-（4-二甲氨基苯基）-1，4-苯醌亚胺，它具有超快的非辐射衰减，由于其灵活的分子结构。通过激发乙醇（EtOH）溶液中的分子与两个激发波长位于较短和较长的波长侧的可见光吸收带，我们观察到超快的非辐射衰减从激发态，然后在基态的光谱演化。亚皮秒范围内的非辐射衰变产生了一个振动热基态，其寿命在皮秒范围内。随后，从热态产生在较短波长下吸收的互变异构体，这导致基态漂白剂（GSB）发生红移。互变异构化可能涉及由溶质和溶剂分子之间的氢键（H-键）断裂引起的苯醌亚胺部分的扭曲。氢键的复合发生的时间常数为30 ps，系统返回到其原始状态。我们还观察到低频相干波包振荡，调制GSB与失相时间类似的激发态寿命。
Femtosecond time-resolved transient absorption spectroscopy was performed for a nonfluorescent solvatochromic dye, phenol blue,N-(4-dimethylaminophenyl)-1,4-benzoquinoneimine, which exhibits ultrafast nonradiative decay due to its flexible molecular structure. By exciting the molecule in ethanol (EtOH) solution with two excitation wavelengths located at shorter- and longer-wavelength sides of the visible absorption band, we observed ultrafast nonradiative decay from the excited state, followed by spectral evolution in the ground state. The nonradiative decay in the subpicosecond range creates a vibrationally hot ground state with the lifetime in the picosecond range. Subsequently, a tautomer that absorbs at shorter wavelengths is produced from the hot state, which causes a red shift of the ground-state bleach (GSB). The tautomerization presumably involves twisting of the benzoquinoneimine moiety induced by the breaking of the hydrogen bond (H-bond) between the solute and the solvent molecules. The recombination of the H-bond occurs with a time constant of ∼30 ps, and the system returns to its original state. We also observed low-frequency coherent wavepacket oscillations that modulate the GSB with dephasing times similar to the excited-state lifetime.