Spectroscopic Characterization of the Divalent Metal Docking Motif to Isolated Cyanobenzoate: Direct Observation of Tridentate Binding to ortho -Cyanobenzoate and Implications for the CN Response
Spectroscopic Characterization of the Divalent Metal Docking Motif to Isolated Cyanobenzoate: Direct Observation of Tridentate Binding to ortho -Cyanobenzoate and Implications for the CN Response
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分离的氰基苯甲酸酯的二价金属对接基序的光谱表征：直接观察三齿酸与邻氰基苯甲酸酯的结合以及对 CN 响应的影响
DOI：
10.1021/acs.jpca.2c07658
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Johnson, Mark A.
中科院分区：
文献类型：
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作者：
Mohamed, Ahmed;Edington, Sean C.;Secor, Maxim;Breton, James R.;Hammes-Schiffer, Sharon;Johnson, Mark A.
D2-标记的氰基苯甲酸酯（CBA）衍生物的低温离子振动光谱的获得和分析，以表征固有的光谱响应的−CO2-头基，其位置上的环在两个孤立的阴离子和阳离子配合物与二价金属离子，M2+（M = Mg，Ca，Sr）。苯甲腈功能建立不同的环异构体（帕拉，Meta，邻位）根据羧酸盐的位置，并提供了一个额外的报告分子响应的近端电荷中心。芳族羧酸盐显示位移略小于观察到的相关脂肪族系统后，金属离子络合。虽然CBA阴离子在所有三个环位置上显示出非常相似的谱带模式，但在与金属离子络合时，邻位异构体在−CO2-部分和CN基团中产生了显着不同的光谱响应。这种行为被追溯到一个独特的thorthoisomer三齿结合基序的出现，其中金属离子结合到羧酸根基团的氧原子和氰基的N原子。在该构型中，−CO2-部分垂直于苯环取向，CN伸缩基函数相对于其在孤立中性中的行为既强又红移。与金属离子末端与−CN的“刘易斯”型结合相关的通常蓝移相反，金属结合的邻位络合物的行为发生。这些光谱特征的起源进行了分析与援助的电子结构计算，这也探讨了预期的一价阳离子的络合theorthocarboxylate的差异。由此产生的见解有影响，了解在化学和生物系统中的金属结合位点的静电和空间相互作用之间的平衡。
Cryogenic ion vibrational spectra of D2-tagged cyanobenzoate (CBA) derivatives are obtained and analyzed to characterize the intrinsic spectroscopic responses of the −CO2–headgroup to its location on the ring in both the isolated anions and the cationic complexes with divalent metal ions, M2+(M = Mg, Ca, Sr). The benzonitrile functionality establishes the different ring isomers (para,meta,ortho) according to the location of the carboxylate and provides an additional reporter on the molecular response to the proximal charge center. The aromatic carboxylates display shifts slightly smaller than those observed for a related aliphatic system upon metal ion complexation. Although the CBA anions display very similar band patterns for all three ring positions, upon complexation with metal ions, theorthoisomer yields dramatically different spectral responses in both the −CO2–moiety and the CN group. This behavior is traced to the emergence of a tridentate binding motif unique to theorthoisomer in which the metal ions bind to both the oxygen atoms of the carboxylate group and the N atom of the cyano group. In that configuration, the −CO2–moiety is oriented perpendicular to the phenyl ring, and the CN stretching fundamental is both strong and red-shifted relative to its behavior in the isolated neutral. The behaviors of the metal-boundorthocomplexes occur in contrast to the usual blue shifts associated with “Lewis” type binding of metal ions end-on to −CN. The origins of these spectroscopic features are analyzed with the aid of electronic structure calculations, which also explore differences expected for complexation of monovalent cations to theorthocarboxylate. The resulting insights have implications for understanding the balance between electrostatic and steric interactions at metal binding sites in chemical and biological systems.