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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electronic structure and proton transfer in ground-state hexafluoroacetylacetone
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Electronic structure and proton transfer in ground-state hexafluoroacetylacetone

机译：基态六氟乙酰丙酮中的电子结构和质子转移

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摘要

The ground electronic state (X?~1A_1) of hexafluoroacetylacetone (HFAA) has been subjected to synergistic experimental and theoretical investigations designed to resolve controversies surrounding the nature of intramolecular hydrogen bonding for the enol tautomer. Cryogenic (93K) X-ray diffraction studies were conducted on single HFAA crystals grown in situ by means of the zone-melting technique, with the resulting electron density maps affording clear evidence for distinguishable O_1-H and HO _2 bonds that span an interoxygen distance of 2.680 ± 0.003 ?. Such laboratory findings have been corroborated by a variety of quantum chemical methods including Hartree-Fock (HF), density functional [DFT (B3LYP)], M?ller-Plesset perturbation (MPn), and coupled cluster [CCSD, CCSD(T)] treatments built upon extensive sets of correlation-consistent basis functions. Geometry optimizations performed at the CCSD(T)/aug-cc-pVDZ level of theory predict an asymmetric (C_s) equilibrium configuration characterized by an O?O donor-acceptor separation of 2.628 ?. Similar analyses of the transition state for proton transfer reveal a symmetric (C_(2v)) structure that presents a potential barrier of 21.29 kJ/mol (1779.7 cm ~(-1)) height. The emerging computational description of HFAA is in reasonable accord with crystallographic measurements and suggests a weakening of hydrogen-bond strength relative to that of the analogous acetylacetone molecule.
机译：六氟乙酰丙酮（HFAA）的基态电子状态（Xα〜1A_1）经过协同实验和理论研究，旨在解决有关烯醇互变异构体分子内氢键键合性质的争议。通过区域熔化技术对原位生长的单个HFAA晶体进行了低温（93K）X射线衍射研究，所得电子密度图为跨氧跨度的O_1-H和HO _2键之间的可分辨键提供了清晰的证据2.680±0.003欧。此类实验室发现已通过多种量子化学方法得到证实，包括Hartree-Fock（HF），密度泛函[DFT（B3LYP）]，M？ller-Plesset微扰（MPn）和耦合簇[CCSD，CCSD（T） ]处理建立在大量的相关一致的基础函数上。在理论上的CCSD（T）/ aug-cc-pVDZ水平上进行的几何优化预测了不对称（C_s）平衡构型，其特征是O？O供体与受体的间距为2.628？。对于质子转移的过渡态的类似分析揭示了对称（C_（2v））结构，该结构呈现出21.29 kJ / mol（1779.7 cm〜（-1））高度的势垒。出现的HFAA的计算描述与晶体学测量结果相当吻合，表明相对于类似的乙酰丙酮分子而言，氢键强度的减弱。

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