The dynamics of photoinduced O–H bond fission in five fluorinated phenols (2-fluorophenol, 3-fluorophenol, 2,6-difluorophenol, 3,4,5-trifluorophenol, and pentafluorophenol) have been investigated by H Rydberg atom photofragment translational spectroscopy following excitation at many wavelengths in the range 220 ≤ λ ≤ 275 nm. The presence of multiple fluorine substituents reduces the efficiency of O–H bond fission (by tunneling) from the first excited (1¹ππ*) electronic state, whereas all bar the perfluorinated species undergo O–H bond fission when excited at shorter wavelengths (to the 2¹ππ* state). As in bare phenol, O–H bond fission is deduced to occur by non-adiabatic coupling at conical intersections between the photoprepared “bright” ππ* states and the 1¹πσ* potential energy surface. In all cases, the fluorophenoxyl photoproducts are found to be formed in a range of vibrational levels, all of which include an odd number of quanta (typically one) in an out-of-plane (a″) vibrational mode; this product vibration is viewed as a legacy of the parent out-of-plane motions that promote non-adiabatic coupling to the dissociative 1¹πσ* potential. The radical products also show activity in in-plane vibrations involving coupled (both in- and out-of-phase) C–O and C–F wagging motions, which can be traced to the impulse between the recoiling O and H atoms and, in detail, are sensitive to the presence (or not) of an intramolecular F···H–O hydrogen bond. Upper limit values for the O–H bond dissociation energies are reported for all molecules studied apart from pentafluorophenol.

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环氟化物对苯酚紫外光解离动力学的影响

通过H Rydberg原子光碎裂平移光谱法研究了五种氟化苯酚（2-氟苯酚，3-氟苯酚，2,6-二氟苯酚，3,4,5-三氟苯酚和五氟苯酚）中光诱导的OH键裂变的动力学。在220≤λ≤275 nm范围内的许多波长处激发。多个氟取代基的存在降低了从第一个激发态（¹ 1ππ*）电子态发生的O-H键裂变（通过隧穿）的效率，而所有的全氟化物质在较短波长下激发时都经历O-H键裂变（到2 ¹ ππ*状态）。像在裸苯酚中一样，通过在光制备的“亮”ππ*态与1 ¹之间的锥形交点处的非绝热偶合，可以推断出O-H键裂变。πσ*势能面。在所有情况下，都发现氟苯氧基光产物是在一定范围的振动水平上形成的，所有这些振动水平都包含面外（a ″）振动模式下的奇数个量子点（通常为一个）。该产品振动被视为母体平面外运动的遗留物，它们促进了非绝热耦合到解离体1 ¹πσ*势。自由基产物还显示出平面内振动的活动，该振动涉及耦合的（同相和异相）C-O和C-F摆动运动，这可以追溯到反冲的O和H原子之间的冲量，具体地说，对分子内F··H–O氢键的存在（或不敏感）。据报道，除五氟苯酚外，所有研究的分子的OH键解离能的上限值。