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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Probing the Molecular and Electronic Structure of Norhipposudoric and Hipposudoric Acids from the Red Sweat of Hippopotamus amphibius: A DFT Investigation
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Probing the Molecular and Electronic Structure of Norhipposudoric and Hipposudoric Acids from the Red Sweat of Hippopotamus amphibius: A DFT Investigation

机译：从两栖河马的红色汗中探查正庚二酸和正七酸的分子和电子结构：DFT研究

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摘要

Molecular structure and tautomeric/conformational preferences of norhipposudoric and hipposudoric acids,the recently isolated pigments of the Hippopotamus amphibius sweat, were investigated using the density functional theory (DFT) PBE0 formalism. Among a large variety of possible structures, two similar keto-enol tautomer/conformers are nearly isoenergetic and markedly more stable than the others both in the gas phase and aqueous solution. The bulk solvent effect was accounted for with the polarizable continuum model (PCM). A distinctive structural feature is the strong intramolecular hydrogen bonding in the keto-enol O-HO bridge, as shown by analysis of the atoms-in-molecules topological properties of the electron density. To elucidate the claimed strong acidity of these pigments, the site-specific microscopic dissociation constants were also calculated using the cluster-continuum model, a hybrid approach based on inclusion of explicit solvent molecules and solvation of the cluster by the dielectric continuum. Notably, the first deprotonation should occur predominantly from the enolic group with a remarkably low pki value. This factor could play an important role in the potent antibiotic activity of the pigments. The absorption spectra of the undissociated and dissociated compounds in aqueous solution were interpreted with time-dependent DFT/PCM calculations.The -* diquinoid excitations, mainly occurring in the fluorenoid nucleus, are the major contributors to the color and strong absorption bands in the UVA and UVB regions, which are closely related to the efficient sunscreen activity exerted by the pigments.
机译：使用密度泛函理论（DFT）PBE0形式论研究了正庚二酸和马六丁酸（最近被分离的两栖河马汗色素）的分子结构和互变异构/构象偏好。在各种各样的可能结构中，两种相似的酮-烯醇互变异构体/异构体在气相和水溶液中几乎是等能量的，并且比其他的稳定得多。大量溶剂效应是由可极化连续体模型（PCM）解决的。独特的结构特征是在酮-烯醇O-HO桥中强大的分子内氢键，如通过分析电子密度的分子内原子拓扑特性所示。为了阐明所要求的这些颜料的强酸性，还使用簇连续谱模型（基于包含显式溶剂分子和簇通过介电连续峰溶剂化的混合方法）计算了特定于位点的微观解离常数。值得注意的是，第一次去质子化应主要发生在烯醇基团中，pki值极低。该因素可能在色素的有效抗生素活性中起重要作用。通过时间依赖的DFT / PCM计算来解释水溶液中未离解和离解的化合物的吸收光谱。-*二喹啉激发主要发生在芴核中，是造成UVA颜色和强吸收谱带的主要因素UVB和UVB区域，与颜料发挥的有效防晒活性密切相关。

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