Chlorine Substitution Effect on the S1 Relaxation Dynamics of Chlorobenzene and Chlorophenols.

IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL
The Journal of Physical Chemistry A Pub Date : 2024-12-19 Epub Date: 2024-12-04 DOI:10.1021/acs.jpca.4c05995
Junggil Kim, Sang Kyu Kim
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引用次数: 0

Abstract

The S1 state relaxation dynamics of chlorobenzene (CB), 3-chlorophenol (3-CP), 3-CP·H2O, and 2-chlorophenol·H2O (2-CP·H2O) have been investigated by means of picosecond time-resolved pump-probe spectroscopy in a state-specific manner. For CB, the S1 state relaxes via the S1-S0 internal conversion in the low internal energy region (<2000 cm-1), whereas the direct C-Cl bond dissociation channel mediated by the upper-lying repulsive πσCCl* state is opened to give the rather sharp increase of the S1 relaxation rate in the high internal energy region (>2000 cm-1). A similar dynamic feature has been observed for 3-CP in terms of the lifetime behavior with an increase in the S1 internal energy, suggesting that the H atom tunneling dissociation reaction from OH might contribute less compared to the internal conversion, although it is not clear at the present time whether or not the sharp increase of the S1 relaxation rate in the high internal energy region of 3-CP (>1500 cm-1) is entirely due to that of the internal conversion. The fact that the internal conversion is facilitated by the Cl substitution implies that the energetic location of the S1/S0 conical intersection should have been strongly influenced by chlorine substitution on the aromatic ring. The approximate energetic location of the saddle point of the S1(ππ*)/πσCCl* conical intersection along the seam coordinate for CB or 3-CP could be inferred from the energy-dependent S1 lifetime measurements. It is discussed in comparison with the dynamic role of the S1(ππ*)/πσCCl* conical intersection, which is strongly influenced by the O-H···Cl intramolecular hydrogen bond in the rather complicated yet ultrafast S1 relaxation dynamics of the cis-2-CP. The S1 lifetimes of 3-CP·H2O and 2-CP·H2O reveal the importance of the conformational structures, especially in terms of the intramolecular hydrogen bonding.

氯取代效应对氯苯和氯酚S1弛豫动力学的影响。
利用皮秒时间分辨泵浦探针光谱研究了氯苯(CB)、3-氯酚(3-CP)、3-氯酚·H2O和2-氯酚·H2O (2-CP·H2O)的S1态弛豫动力学。对于CB, S1态在低内能区(-1)通过S1- s0内转换松弛,而由上层斥力πσCCl*态介导的C-Cl键直接解离通道被打开,使得S1在高内能区(>2000 cm-1)松弛速率急剧增加。随着S1内能的增加,3-CP的寿命行为也有类似的动态特征,这表明与内部转化相比,H原子对OH的隧道解离反应可能贡献较小,尽管目前尚不清楚3-CP的高内能区(>1500 cm-1) S1弛豫速率的急剧增加是否完全是由于内部转化。Cl取代促进了内部转化的事实表明,S1/S0锥形交点的能量位置应该受到芳香环上氯取代的强烈影响。从能量依赖的S1寿命测量可以推断出CB或3-CP沿煤层坐标的S1(ππ*)/πσCCl*锥形交点鞍点的近似能量位置。比较了分子内氢键O-H···Cl对S1(ππ*)/πσCCl*圆锥交点在顺-2- cp复杂的超快S1弛豫动力学中的动力学作用。3-CP·H2O和2-CP·H2O的S1寿命揭示了构象结构的重要性,特别是在分子内氢键方面。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
The Journal of Physical Chemistry A
The Journal of Physical Chemistry A 化学-物理:原子、分子和化学物理
CiteScore
5.20
自引率
10.30%
发文量
922
审稿时长
1.3 months
期刊介绍: The Journal of Physical Chemistry A is devoted to reporting new and original experimental and theoretical basic research of interest to physical chemists, biophysical chemists, and chemical physicists.
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