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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Toward Organic Superbases: The Electronic Structure and the Absolute Proton Affinity of Quinodiimines and Some Related Compounds
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Toward Organic Superbases: The Electronic Structure and the Absolute Proton Affinity of Quinodiimines and Some Related Compounds

机译：迈向有机超强碱：奎尼丁亚胺和一些相关化合物的电子结构和绝对质子亲和力

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摘要

Several molecular systems that may well serve as potent organic superbases are examined by using ab initio and semiempirical theoretical models. It is found that the imino group attached to the semiquinoid fragment or to a backbone of several quinoid six-membered rings exhibits a very high proton affinity (PA). It is found that the reason behind their amplified basicity is appreciable aromatization of the quinoid building blocks upon protonation. The underlying mechanism in extended systems is that of the aromaticity spin-off effect, triggered by the proton attack at the imino N atom and spread along the quinoid ribbon in a typical domino fashion. It yields an increase in the PA as high as roughly 20 kcal/mol per the quinoid ring. Susceptibility toward the proton attack is further amplified by the alkyl substitution at the imino nitrogen atom and by additional substitution of the amino groups at specific positions within the framework of the quinoid building block(s). It is stressed that synthesis of the studied systems might provide very potent organic superbases.
机译：通过使用从头算和半经验理论模型，研究了几种很可能用作有效有机超碱的分子系统。发现连接到半喹啉片段或几个醌六元环的主链上的亚氨基基团表现出非常高的质子亲和力（PA）。发现它们的碱性增加的原因是质子化时醌类结构单元的明显芳构化。扩展系统中的潜在机制是芳香性附带效应的机制，该效应是由亚氨基N原子上的质子攻击触发的，并以典型的多米诺骨牌方式沿醌带扩散。每个quinoid环的PA升高高达约20 kcal / mol。通过在亚氨基氮原子上的烷基取代和在醌型结构单元的框架内特定位置的氨基的额外取代，进一步增强了对质子攻击的敏感性。需要强调的是，所研究系统的合成可能会提供非常有效的有机超碱。

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