de Andrade Karine N, Raffaeli Natalia M, Fiorot Rodolfo G
Department of Organic Chemistry, Institute of Chemistry, Universidade Federal Fluminense (UFF), Outeiro de São João Batista, Niterói, Rio de Janiero 24020-141, Brazil.
Inorg Chem. 2025 Jun 16;64(23):11683-11695. doi: 10.1021/acs.inorgchem.5c01132. Epub 2025 Jun 3.
Developing novel molecular switches requires structural modifications that yield isomers with distinct photophysical properties. Akamptisomerism ─ a bond angle reflection (BAR) process occurring in low-symmetry porphyrins bridged by (F)B-O-B(F) units ─ induces distortions from the porphyrin pseudoplane, offering a promising strategy for optoelectronic switching. Herein, we report the first quantum chemical investigation of BAR in β- and -substituted porphyrinoid systems as a potential switching mechanism. Density functional theory (DFT) calculations (B3LYP-D3/def2-QZVP//B3LYP-D3/6-31+G**) confirm the occurrence of ()-akamptisomerism in all evaluated compounds, featuring a thermal interconversion barrier ( → ) of 26.6 ± 2.1 kcal mol that is largely unaffected by porphyrin substitution across 28 compounds. Simulated UV-vis spectra (TD-CAM-B3LYP/6-31+G**) reveal that β,β-push-pull systems bearing -NMe and -NO groups on opposite pseudoplanes, combined with -Bu substitution, exhibit significant spectral differentiation between akamptisomers (Δ / = 320.6 meV, at the S state). This shift arises from intramolecular charge transfer between pseudoplanes and steric distortion induced by the -Bu group. These findings establish akamptisomerism as a viable platform for constructing molecular building blocks with distinct optical signatures. Moreover, they underscore how substitution patterns can be exploited to tune the photophysical properties of BAR systems, providing valuable insights for the rational design of next-generation switchable materials.
开发新型分子开关需要进行结构修饰，以产生具有不同光物理性质的异构体。阿克姆异构现象——一种发生在由(F)B - O - B(F)单元桥接的低对称卟啉中的键角反射（BAR）过程——会导致卟啉假平面产生畸变，为光电开关提供了一种有前景的策略。在此，我们报告了对β - 和 - 取代的类卟啉体系中BAR作为潜在开关机制的首次量子化学研究。密度泛函理论（DFT）计算（B3LYP - D3/def2 - QZVP//B3LYP - D3/6 - 31 + G**）证实了所有评估化合物中均存在() - 阿克姆异构现象，其热互变势垒（→）为26.6±2.1 kcal mol，在28种化合物中，该势垒在很大程度上不受卟啉取代的影响。模拟的紫外 - 可见光谱（TD - CAM - B3LYP/6 - 31 + G**）表明，在相对的假平面上带有 - NMe和 - NO基团且结合 - Bu取代的β,β - 推拉体系，在阿克姆异构体之间表现出显著的光谱差异（在S态下，Δ/ = 320.6 meV）。这种位移源于假平面之间的分子内电荷转移以及 - Bu基团引起的空间畸变。这些发现确立了阿克姆异构现象作为构建具有独特光学特征的分子构建块的可行平台。此外，它们强调了如何利用取代模式来调节BAR体系的光物理性质，为下一代可切换材料的合理设计提供了有价值的见解。
