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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Protonation of Bipyridines and Their Vinylene-Phenylene-Vinylene Derivatives: Theoretical Analysis of the Positive Charge Effects
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Protonation of Bipyridines and Their Vinylene-Phenylene-Vinylene Derivatives: Theoretical Analysis of the Positive Charge Effects

机译：联吡啶及其乙烯-苯撑-亚乙烯基衍生物的质子化：正电荷效应的理论分析

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摘要

Torsion analysis of the bipyridine (BPy) segment was carried out on the free and protonated bipyridines (head-to-head) as well as their vinylene-phenylene-vinylene (VPV) derivatives with semiempirical AM1 calculations to determine the configuration of protonated species. The hydrogen bonding energy has been estimated through comparison of the energy barriers with those of the free base form. Intramolecular hydrogen bonding plays an important role in the ring torsion where one nitrogen atom is protonated. Torsion potentials are prodominated by repulsion between the positive charges where both nitrogen atoms are protonated. Proton bonding to nitrogen has strong electron withdrawing effect. It stabilizes the HOMO and LUMO, with the second being the most affected. Consequently, protonation decreases the HOMO/LUMO energy gap. These protonation effects will be gradually reduced as the counterions come closer to the protons. The first transition energies were calculated with ZINDO/SCI methods and compared with the AM1 calculated HOMO/LUMO energy gaps at various torsion angles. The theoretical results support the ion-induced as well as protonation induced red-shifting of both the absorption and emission maximum of bipyridine contained polymers.
机译：对联吡啶（BPy）段进行了扭转分析，对游离和质子化联吡啶（头对头）及其亚乙烯基-亚苯基-亚乙烯基（VPV）衍生物进行了半经验AM1计算，以确定质子化物种的构型。通过将能垒与游离碱形式的能垒进行比较来估计氢键能。分子内氢键在一个氮原子质子化的环扭转中起重要作用。扭转势主要由两个氮原子都质子化的正电荷之间的排斥力决定。质子与氮的键合具有很强的吸电子作用。它使HOMO和LUMO稳定下来，受影响最大的是第二个。因此，质子化减小了HOMO / LUMO能隙。随着反离子离质子越来越近，这些质子化效应将逐渐降低。用ZINDO / SCI方法计算出第一跃迁能，并与AM1在不同扭转角下计算出的HOMO / LUMO能隙进行比较。理论结果支持了联吡啶所含聚合物的最大吸收和发射的离子诱导以及质子诱导的红移。

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