FLUORESCENCE-DIP INFRARED SPECTROSCOPY OF JET-COOLED 5-HYDROXYTROPOLONE
FLUORESCENCE-DIP INFRARED SPECTROSCOPY OF JET-COOLED 5-HYDROXYTROPOLONE
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喷射冷却 5-羟基托酚酮的荧光浸红外光谱
DOI：
10.1021/jp961735m
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
T. Zwier
中科院分区：
文献类型：
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作者：
R. K. Frost;Fredrick C. Hagemeister;Dave Schleppenbach;G. Laurence;T. Zwier
用荧光耗尽法记录了5-羟基环庚三烯酚酮（5-HOTrOH）单体的顺式和反式构象的基态红外光谱。5-羟基基团的“自由”的O-H伸缩，2-羟基分子内氢键的O-H伸缩，和C-H伸缩转换观察到的两种构象。这些频带的分配是明确的裸托酚酮与以前的红外研究相比，并证实了MP2和DFT水平的振动频率和强度计算。每个构象被预测有四个允许的C-H伸缩跃迁。反构象的C-H伸缩带的计算与实验之间存在合理的一一对应关系，而顺构象则表现出费米共振混合效应。顺式和反式构象的5-OH伸缩带分别位于3654和3664 cm-1处。参与分子内氢键的2-OH基团的OH伸缩基本原理集中在3170和3195 cm-1。这些谱带在两种构象异构体中都被广泛加宽，并且包含可重复的亚结构，其不规则间距约为10−15 cm-1。分子内氢键键合的2-羟基O-H伸缩带的亚结构反映了一种选择性的第一层振动态混合，很可能有一组模式与之处于接近二比一的共振状态。最后，H原子隧穿的双最小势阱中249 cm-1的不对称性似乎足以淬灭S 0中的顺反隧穿，即使在激发2-OH伸缩基频之后。没有证据表明，发现syn Participanti的“交叉”转换，尽管仔细搜索能够检测到这样的转换在约1%的耗尽水平。
Ground-state infrared spectra of the syn and anti conformers of jet-cooled 5-hydroxytropolone (5-HOTrOH) monomer have been recorded free from interference from one another using a fluorescence depletion method. The 5-hydroxy group “free” O−H stretch, 2-hydroxy intramolecularly hydrogen-bonded O−H stretch, and C−H stretch transitions are observed for both conformers. The assignment of these bands is clear by comparison with previous infrared studies of bare tropolone and is confirmed by MP2 and DFT level vibrational frequency and intensity calculations. Each of the conformers is predicted to have four allowed C−H stretch transitions. There is a reasonable one-for-one correspondence between calculation and experiment for the anti conformer's C−H stretch bands, while the syn conformer shows effects of Fermi resonance mixing. The 5-OH stretch bands of the syn and anti conformers are single, sharp transitions located at 3654 and 3664 cm-1, respectively. The OH stretch fundamentals of the 2-OH group involved in the intramolecular hydrogen bond are centered on 3170 and 3195 cm-1. These bands are extensively broadened in both conformers and contain reproducible substructure with irregular spacing of about 10−15 cm-1. The substructure of the intramolecularly H-bonded 2-hydroxy O−H stretch band reflects a selective first-tier vibrational-state mixing, most likely with a set of modes which are in near two-to-one resonance with it. Finally, the 249 cm-1asymmetry in the double-minimum potential well for H atom tunneling appears to be sufficient to quench syn−anti tunneling in S0even following excitation of the 2-OH stretch fundamental. No evidence is found for syn ↔ anti “crossover” transitions despite careful searches capable of detecting such transitions at depletion levels of about 1%.