Theoretical study on the distribution of atomic charges in the Schiff bases of 3-hydroxypyridine-4-aldehyde and alanine. The effect of the protonation state of the pyridine and imine nitrogen atoms
Theoretical study on the distribution of atomic charges in the Schiff bases of 3-hydroxypyridine-4-aldehyde and alanine. The effect of the protonation state of the pyridine and imine nitrogen atoms
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DOI：
10.1016/j.chemphys.2008.12.006
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发表时间：
2009-01-27
期刊：
影响因子：
2.3
通讯作者：
Munoz, Francisco
中科院分区：
文献类型：
--
作者：
Casasnovas, Rodrigo;Salva, Antoni;Munoz, Francisco
采用密度泛函理论（DFT）（B3 LYP/6-31+G*）研究了3-羟基吡啶-4-醛与丙氨酸形成的席夫碱及其C α-碳负离子配合物中吡啶和亚胺氮原子的质子化状态对“电子汇”效应的影响，结果表明，吡啶氮的质子化促进了烯醇亚胺-酮烯胺互变异构.吡啶氮对碳负离子分子中的“电子汇”效应的重要性显然取决于亚胺氮的质子化状态：在烯醇亚胺互变异构体中，亚胺氮被去质子化，70%的电子电荷在吡啶环上离域，而在酮烯胺型结构中。当亚胺氮被完全质子化时，只有20%的电荷在该分子部分中离域。结果进行了讨论，在一些PLP依赖性酶的化学和它们的活性位点的结构。(C)2008 Elsevier B. V.保留所有权利。
The protonation state of the pyridine and imine nitrogen atoms on the "electron-sink" effect was studied by DFT(B3LYP/6-31+G*) calculations in the Schiff bases formed between 3-hydroxypyridine-4-aldehyde and alanine and their C alpha-carbanionic counterparts.Results indicate that the protonation of pyridine nitrogen promotes the enolimine-ketoenamine tautomerism. The importance of pyridine nitrogen on the "electron-sink" effect in the carbanionic molecules clearly depends on the protonation state of the imine nitrogen: in the enolimine tautomers, where the imine nitrogen is deprotonated, a 70% of the electron charge is delocalized on the pyridine ring, whereas in the ketoenamine type structures. where the imine nitrogen is fully protonated, just a 20% of this charge is delocalized in this Molecular moiety. The results are discussed in relation to the chemistry of some PLP-dependent enzymes and the Structure of their active sites. (C) 2008 Elsevier B.V. All rights reserved.