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首页> 外文期刊>Chemistry: A European journal >Versatile Photophysical Properties of meso-Aryl-Substituted Subporphyrins:Dipolar and Octupolar Charge-Transfer Interactions
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Versatile Photophysical Properties of meso-Aryl-Substituted Subporphyrins:Dipolar and Octupolar Charge-Transfer Interactions

机译：Meso芳基取代的亚卟啉的多功能光物理性质：偶极和八极电荷转移相互作用。

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摘要

Donor–acceptor systems based on subporphyrins with nitro and amino substituents at meta and para positions of the meso-phenyl groups were synthesized and their photophysical properties have been systematically investigated. These molecules show two types of charge-transfer nteractions, that is, from center to periphery and periphery to center depending on the peripheral substitution, in which the subporphyrin moiety plays a dual role as both donor and acceptor. Based on the solvent-polarity-dependent photophysical properties, we have shown that the fluorescence emission of para isomers originates from the olvatochromic, dipolar, symmetry-broken,and relaxed excited states, whereas the non-solvatochromic fluorescence of meta isomers is of the octupolar type with false symmetry breaking. The restricted meso-(4-aminophenyl) rotation at low temperature prevents the intramolecular charge-transfer (ICT)-forming process. The two-photon absorption (TPA) cross-section values were determined by photoexcitation at 800 nm in nonpolar toluene and polar acetonitrile solvents to see the effect of ICT on the TPA processes. The large enhancement in the TPA cross-section value of approximately 3200 GM (1 GM= 1050 cm4 sphoton1) with donor–acceptor substitution has been attributed to the octupolar effect and ICT interactions. A correlation was found between the electron-donating/-withdrawing abilities of the peripheral groups and the TPA cross-section values, that is, paminophenyl> m-aminophenyl>nitrophenyl.The increased stability of octupolarICT interactions in highly polar solvents enhances the TPA cross-section value by a factor of approximately 2 and 4, respectively, for p-amino- and m-nitrophenyl-substituted subporphyrins. On the other hand, the stabilization of the symmetry-broken, dipolar ICT state gives rise to a negligible impact on the TPA processes.
机译：合成了基于亚卟啉的供体-受体系统，亚卟啉在中苯基的间位和对位具有硝基和氨基取代基，并对其光物理性质进行了系统的研究。这些分子表现出两种类型的电荷转移相互作用，即从中心到外围以及从外围到中心，这取决于外围取代，其中亚卟啉部分同时充当供体和受体的双重作用。基于与溶剂极性有关的光物理性质，我们表明对位异构体的荧光发射来自于变色，偶极，对称断裂和弛豫的激发态，而间位异构体的非变色荧光是八极的。带有错误的对称破坏类型。在低温下受限的内消旋-（4-氨基苯基）旋转阻止了分子内电荷转移（ICT）的形成过程。通过在非极性甲苯和极性乙腈溶剂中在800 nm处进行光激发来确定两光子吸收（TPA）的横截面值，以了解ICT对TPA工艺的影响。通过供体-受体的替代，TPA横截面值大幅度提高，约为3200 GM（1 GM = 1050 cm4 sphoton1），这归因于八极效应和ICT相互作用。发现外围基团的供电子/吸电子能力与TPA横截面值之间有相关性，即对氨基苯基>间氨基苯基>硝基苯基。在高极性溶剂中八极性ICT相互作用增加的稳定性增强了TPA交叉对氨基和间硝基苯基取代的亚卟啉的截面积值分别约为2和4。另一方面，对称性破损的偶极ICT状态的稳定对TPA流程的影响可忽略不计。

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