Phlorins have long remained underexplored relative to their fully conjugated counterparts, such as porphyrins, hydroporphyrins, and corroles. Herein, we have attempted to bridge that knowledge gap with a scalar-relativistic density functional theory (DFT) study of unsubstituted iridium and gold phlorin derivatives and a multitechnique experimental study of iridium-bispyridine and gold complexes of 5,5-dimethyl-10,15,20-tris(pentafluorophenyl)phlorin. Theory and experiments concur that the phlorin derivatives exhibit substantially smaller HOMO–LUMO gaps, as reflected in a variety of observable properties. Thus, the experimentally studied Ir and Au complexes absorb strongly in the near-infrared (NIR), with absorption maxima at 806 and 770 nm, respectively. The two complexes are also weakly phosphorescent with emission maxima at 950 and 967 nm, respectively. They were also found to photosensitize singlet oxygen formation, with quantum yields of 40 and 28%, respectively. The near-infrared (NIR) absorption and emission are consonants with smaller electrochemical HOMO–LUMO gaps of ∼1.6 V, compared to values of ∼2.1 V, for electronically innocent porphyrins and corroles. Interestingly, both the first oxidation and reduction potentials of the Ir complex are some 600 mV shifted to more negative potentials relative to those of the Au complex, indicating an exceptionally electron-rich macrocycle in the case of the Ir complex.

中文翻译：

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金属齿甙的电子结构：铱和金齿甙衍生物的经验教训


相对于其完全缀合的对应物，例如卟啉、氢卟啉和咔咯，长期以来，根皮素一直未被充分研究。在此，我们试图通过对未取代的铱和金phlorin衍生物的标量相对论密度泛函理论（DFT）研究以及对铱-双吡啶和5,5-二甲基-10金络合物的多技术实验研究来弥补这一知识差距， 15,20-三(五氟苯基)弗洛林。理论和实验一致认为，根皮苷衍生物表现出更小的 HOMO-LUMO 间隙，这反映在各种可观察到的特性中。因此，实验研究的 Ir 和 Au 配合物在近红外 (NIR) 区域有强烈吸收，吸收最大值分别为 806 和 770 nm。这两种配合物也具有弱磷光，发射最大值分别为 950 和 967 nm。它们还被发现对单线态氧的形成具有光敏性，量子产率分别为 40% 和 28%。对于电子无害的卟啉和咔咯，近红外（NIR）吸收和发射与较小的电化学 HOMO-LUMO 能隙（约 1.6 V）相一致，而电化学 HOMO-LUMO 能隙为约 2.1 V。有趣的是，相对于 Au 络合物，Ir 络合物的第一氧化和还原电势均转移至更负的电势约 600 mV，这表明 Ir 络合物具有异常富电子的大环。