Bayach Imene, Al-Faiyz Yasair S S, Alkhalifah Mohammed A, Almutlaq Nadiah, Ayub Khurshid, Sheikh Nadeem S
Department of Chemistry, College of Science, King Faisal University, Al-Ahsa 31982, Saudi Arabia.
Department of Chemistry, COMSATS University, Abbottabad Campus, Khyber Pakhtunkhwa 22060, Pakistan.
ACS Omega. 2022 Sep 27;7(40):35863-35874. doi: 10.1021/acsomega.2c04231. eCollection 2022 Oct 11.
The UV-vis absorption characteristics and nonlinear optical properties of a series of substituted dihydroazulene (DHA)/vinylheptafulvene (VHF) photoswitches are investigated by applying quantum calculations. Introduction of substituents at the seven-membered ring resulted in significant changes in their absorption properties depending on the nature and position of the substituent. Electron-donating groups at positions 5, 6, 7, and 8 generally exhibited red shifts with respect to the parent compound. However, the steric effect at positions 8a and 4 is responsible for the loss of planarity and conjugation, which generally leads to blue shifts. In contrast, any electron-withdrawing group, particularly at positions 8a and 4, would cause a blue shift. The presence of bulky groups at position 8a results in a loss of planarity and, as a result, a decrease in electronic conjugation within the molecule, resulting in a blue shift in the maximum absorption. When it comes to halogens, the red shift is directly correlated to the nucleophilicity; the higher the nucleophilicity, the larger the red shift. Regarding hyperpolarizability, the charge separation induces higher hyperpolarizabilities for all substituted VHFs compared to the corresponding DHAs, resulting in a much higher NLO response. In addition, for all DHA and VHF, the highest values of hyperpolarizabilities are calculated for 6-substituted systems. Finally, the objective of this detailed theoretical investigation is to continue exploring the photophysical properties of DHA-VHF through structural modifications.
通过量子计算研究了一系列取代二氢薁（DHA）/乙烯基七富烯（VHF）光开关的紫外可见吸收特性和非线性光学性质。在七元环上引入取代基会根据取代基的性质和位置导致其吸收特性发生显著变化。5、6、7和8位的供电子基团相对于母体化合物通常表现出红移。然而，8a和4位的空间效应导致平面性和共轭性丧失，这通常会导致蓝移。相比之下，任何吸电子基团，特别是在8a和4位，都会引起蓝移。8a位存在庞大基团会导致平面性丧失，结果分子内的电子共轭减少，导致最大吸收发生蓝移。对于卤素，红移与亲核性直接相关；亲核性越高，红移越大。关于超极化率，与相应的DHA相比，电荷分离导致所有取代的VHF具有更高的超极化率，从而产生更高的非线性光学响应。此外，对于所有的DHA和VHF，计算得出6-取代体系的超极化率最高。最后，这项详细理论研究的目的是通过结构修饰继续探索DHA-VHF的光物理性质。
