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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photoelectron Spectroscopy of Biacetyl and Its Cluster Anions
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Photoelectron Spectroscopy of Biacetyl and Its Cluster Anions

机译：BiaceTyl的光电子光谱和其簇阴离子

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摘要

Photoelectron spectroscopy of the biacetyl (dimethylglyoxal) anion reveals the properties of the ground singlet and lowest triplet electronic states of the neutral biacetyl (BA) molecule. Due to the broad and congested nature of the singlet transition, which peaks at a vertical detachment energy VDE = 1.12(5) eV, only an upper bound of the adiabatic electron affinity of BA could be determined: EA(BA) < 0.7 eV. A narrower and more structured triplet band peaking at VDE = 3.17(2) eV reveals the adiabatic electron binding energy of the triplet to be 3.05(2) eV. These results are in good agreement with ab initio (coupled-cluster) calculations. The lowest-energy structures of the anion, singlet, and triplet states of biacetyl are characterized by different orientations of the methyl groups within the molecular frame. In the ground singlet state of neutral BA, the methyl torsion is offset by similar to 60 degrees compared to that of the anion, while in the triplet the methyl orientation is similar to that of the anion. Photoelectron spectra of the cluster anions reveal that the intermolecular interactions in the homogeneously solvated (BA)(n)(-); clusters are significantly stronger than the interactions of BA(-) with N2O or even of BA(-) with H2O. To account for these observations, pi-pi-bonded structures of the dimer and trimer anions of biacetyl are proposed based on density-functional theory calculations. The analysis of the proposed structures indicates that the negative charge in the (BA)(n)(-) cluster anions, at least in the dimer and the trimer, is significantly delocalized between all BA moieties present and there is a significant degree of covalent bonding within the cluster.
机译：BiaceTyl（二甲基乙醛）阴离子的光电子光谱揭示了地面单六乙酰（BA）分子的接地单态和最低三重态电子状态的性质。由于单向转变的宽泛和拥挤性，垂直脱离能量Vde = 1.12（5）EV的峰，可以确定BA的绝热电子亲和力的上界：EA（Ba）<0.7eV。在VDE = 3.17（2）EV时达到较窄和更具结构化的三重态带峰值，揭示了三联物的绝热电子结合能量为3.05（2 )EV。这些结果与AB Initio（耦合群集）计算吻合良好。阴离子，单态和三乙酰基的最低能量结构，其特征在于分子框架内的甲基的不同取向。在中性BA的地面单态状态中，与阴离子相比，甲基扭转偏移与60度相比，而在三态中，甲基取向类似于阴离子的相比。簇阴离子的光电子光谱揭示了均匀溶剂（Ba）（n）（ - ）中的分子间相互作用;簇明显强于BA（ - - ）与N2O或甚至与H2O的Ba（ - ）的相互作用。为了考虑这些观察结果，基于密度官能理论计算，提出了二聚体和三聚片段的PI-PI键合结构。所提出的结构的分析表明（BA）（N）（ - ）簇阴离子中的负电荷，至少在二聚体和三聚体中，在存在的所有BA部分之间显着截然化，并且存在显着的共价值在群集中绑定。

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