Soltani Marzieh, Minakar Reza, Memarian Hamid R, Sabzyan Hassan
Department of Chemistry , University of Isfahan , 81746-73441 Isfahan , I. R. Iran.
J Phys Chem A. 2019 Apr 4;123(13):2820-2830. doi: 10.1021/acs.jpca.9b00642. Epub 2019 Mar 18.
Cyclic voltammetry is used to derive HOMO energies of the 1-phenyl-2-pyrazolines containing electron-donating or electron-withdrawing substituted phenyl rings and or naphthalenyl substitution on the C- or C-positions of the heterocyclic ring to investigate the steric and electronic effects of the aryl substitutions and the type of aryl system on their electrochemical behaviors. The optical HOMO-LUMO gaps needed for the calculation of LUMO (excited state) energies of these compounds are obtained from their UV-vis spectra. Results show that the substitution on the C-aryl ring has significant effect via its π-donor/acceptor ability, compared to the σ-donor/acceptor ability of the C-aryl ring, on the CV oxidation peak and onset potentials. Comparative analysis showed very good agreement between the experimentally obtained HOMO and (apparent) LUMO energies and the (TD)DFT/6-311++G(d,p) calculated ground and excited states energies. These computational results indicate also that for all chloro- and methoxy-substituted 2-pyrazolines, the HOMO → LUMO is the most intense transition. While the strong acceptor NO substitution on all positions of either C- or C-aryl rings, except for one compound, increases the intensity of the HOMO → LUMO+1 (LUMO+2) transition significantly, the first (the first two) transition(s) HOMO → LUMO (and HOMO → LUMO+1) has (have) much smaller or negligible intensity (intensities).
循环伏安法用于推导含供电子或吸电子取代苯环以及在杂环的C或C位有萘基取代的1-苯基-2-吡唑啉的最高占据分子轨道（HOMO）能量，以研究芳基取代的空间和电子效应以及芳基体系类型对其电化学行为的影响。这些化合物计算最低未占分子轨道（LUMO，激发态）能量所需的光学HOMO-LUMO能隙从其紫外可见光谱中获得。结果表明，与C芳基环的σ供体/受体能力相比，C芳基环上的取代通过其π供体/受体能力对循环伏安氧化峰和起始电位有显著影响。对比分析表明，实验获得的HOMO和（表观）LUMO能量与（含时）密度泛函理论（TD）DFT/6-311++G（d，p）计算的基态和激发态能量之间有很好的一致性。这些计算结果还表明，对于所有氯代和甲氧基取代的2-吡唑啉，HOMO→LUMO是最强的跃迁。虽然除一种化合物外，C或C芳基环所有位置上的强受体NO取代会显著增加HOMO→LUMO+1（LUMO+2）跃迁的强度，但第一个（前两个）跃迁HOMO→LUMO（和HOMO→LUMO+1）的强度要小得多或可忽略不计。
