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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Lowest n,π~* Triplet State of 2-Cyclopenten-1-one: Cavity Ringdown Absorption Spectrum and Ring-Bending Potential-Energy Function
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Lowest n,π~* Triplet State of 2-Cyclopenten-1-one: Cavity Ringdown Absorption Spectrum and Ring-Bending Potential-Energy Function

机译：2-Cyclopenten-1-one的最低n，π〜*三重态：腔衰荡吸收光谱和环弯曲势能函数

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The room-temperature cavity ringdown absorption spectra of 2-cyclopenten-1 one (2CP) and deuterated derivative were recorded near 385 nm. The very weak (∈ < 1 M~(-1) cm~(-1)) band system in this region is due to the T_1←S_0 electronic transition, where T_1 is the lowest-energy ~3(n,π~*) state. The origin band was observed at 25 963.55(7) cm~(-1) for the undeuterated molecule and at 25 959.38(7) and 25 956.18(7) cm~(-1) for 2CP-5-d_1 and 2CP-5,5-d_2, respectively. For the -d_0 isotopomer, about 50 vibronic transitions have been assigned in a region from -500 to +500 cm~(-1) relative to the origin band. Nearly every corresponding assignment was made in the -d_2 spectrum. Several excited-state fundamentals have been determined for the d_0/d_2 isotopomers, including ring-twisting (ν'_(29) = 238.9/227.8 cm~(-1)), out-of-plane carbonyl deformation (ν'_(28) = 431.8/420.3 cm~(-1)), and in-plane carbonyl deformation (ν'_(19) = 346.2/330.2 cm~(-1)). The ring-bending (ν'_(30)) levels for the T_1 state were determined to be at 36.5, 118.9, 213.7, 324.5, and 446.4 cm~(-1) for the undeuterated molecule. These drop to 29.7, 101.9, 184.8, 280.5, and 385.6 cm~(-1) for the -d_2 molecule. A potential-energy function of the form V = ax~4 + bx~2 was fit to the ring-bending levels for each isotopic species. The fitting procedure utilized a kinetic-energy expansion that was calculated based on the structure obtained for the triplet state from density functional calculations. The barrier to planarity, determined from the best-fitting potential-energy functions for the -d_0, -d_1, and -d_2 species, ranges from 42.0 to 43.5 cm~(-1). In the T_1 state, electron repulsion resulting from the spin flip favors nonplanarity. The S_0 and S_1 states have planar structures that are stabilized by conjugation.
机译：在385 nm附近记录了2-cyclopenten-1 one（2CP）和氘代衍生物的室温腔衰荡吸收光谱。该区域中非常弱的（ε<1 M〜（-1）cm〜（-1））带系统是由于T_1←S_0电子跃迁引起的，其中T_1是最低能量〜3（n，π〜* ）状态。对于未氘化的分子，在25 963.55（7）cm〜（-1）处观察到原始带，对于2CP-5-d_1和2CP-5，在25 959.38（7）和25 956.18（7）cm〜（-1）处观察到原始带。 ，5-d_2。对于-d_0同位素，相对于原始谱带，在-500至+500 cm〜（-1）区域分配了约50个振动跃迁。几乎每个对应的分配都是在-d_2频谱中进行的。已经确定了d_0 / d_2异构体的几种激发态基本原理，包括环扭曲（ν'_（29）= 238.9 / 227.8 cm〜（-1）），面外羰基变形（ν'_（ 28）= 431.8 / 420.3 cm〜（-1））和面内羰基变形（ν'_（19）= 346.2 / 330.2 cm〜（-1））。对于未氘化的分子，T_1状态的环弯曲（v'_（30））水平确定为36.5、118.9、213.7、324.5和446.4 cm〜（-1）。对于-d_2分子，这些下降至29.7、101.9、184.8、280.5和385.6cm-1（-1）。 V = ax〜4 + bx〜2形式的势能函数适合每个同位素物种的环弯曲水平。拟合过程利用了动能膨胀，该动能膨胀是基于从密度泛函计算中为三重态得到的结构计算得出的。根据-d_0，-d_1和-d_2物种的最佳拟合势能函数确定的平面性势垒范围为42.0至43.5 cm〜（-1）。在T_1状态下，自旋翻转产生的电子排斥力促进了非平面性。 S_0和S_1状态具有通过共轭稳定的平面结构。

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