Federal University of ABC - UFABC, Av. dos Estados 5001, Santo Andre, SP, Brazil.
Dalton Trans. 2020 Nov 25;49(45):16154-16165. doi: 10.1039/d0dt00436g.
In the present study, the photophysical properties and preliminary time-dependent density functional theory (TD-DFT) data of new rhenium(i) polypyridyl compounds, fac-[Re(L)(Am2phen)(CO)3]0/+, where Am2phen = 4,7-diamine-1,10-phenanthroline and L = Cl and ethyl isonicotinate (et-isonic), provided new insights into excited-state deactivation through an unusual inversion between two metal-to-ligand charge-transfer excited states. In addition, their cellular uptake using breast cancer (MCF-7) and melanoma (SkMel-147 and SkMel-29) cell lines and bioactivity were investigated and their cell-killing mechanism and protein expression were also studied. Preliminary TD-DFT results showed that both compounds exhibited a strong and broad absorption band around 300-400 nm which corresponds to a combination of ILAm2phen and MLCTRe→Am2phen transitions, and a strong contribution of charge transfer transition MLCTRe→et-isonic for fac-[Re(et-isonic)(Am2phen)(CO)3]+ is also observed. In contrast to typical Re(i) polypyridyl complexes, the substitution of Cl with the et-isonic ligand showed a bathochromic shift of the emission maxima, relatively low emission quantum yield and fast lifetime. Photophysical investigation of the fac-[ReCl(et-isonic)2(CO)3] compound provided meaningful information on the excited state manifold of the fac-[Re(L)(Am2phen)(CO)3]0/+ complexes. As shown in the absorption profile, a remarkable inversion of the lowest-lying excited state takes place from the usually observed MLCTRe→Am2phen to the unusual MLCTRe→et-isonic. The lipophilicity of the positive-complex was higher than that of the non-charge compound and the same trend for the activity against cells was observed, in the absence of light. In addition, flow cytometry and Western Blot analyses showed an overexpression of pro-caspase-9, suggesting a caspase proteolytic cascade through an intrinsic-pathway apoptosis mechanism. The photophysical properties of these compounds reported herein provide new fundamental insights into the understanding of substituent groups on polypyridyl ligands which are relevant to practical development.
在本研究中，我们合成了新型的铼（I）金属有机配合物[Re(L)(Am2phen)(CO)3]+（fac-[Re(L)(Am2phen)(CO)3]0/+），并对其光物理性质和初步的时间依赖密度泛函理论（TD-DFT）数据进行了研究。其中，L = Cl 和乙基异烟酸酯（et-isonic），Am2phen = 4,7-二氨基-1,10-菲咯啉。该配合物的电子结构和光物理性质为研究配体取代基对金属有机配合物的影响提供了新的思路。此外，我们还研究了这些配合物在乳腺癌（MCF-7）、黑色素瘤（SkMel-147 和 SkMel-29）细胞系中的摄取情况及其生物活性，并研究了它们的细胞杀伤机制和蛋白表达情况。初步的 TD-DFT 结果表明，这两种配合物都在 300-400nm 左右表现出强烈而宽的吸收带，这对应于 ILAm2phen 和 MLCTRe→Am2phen 跃迁的组合，并且 fac-[Re(et-isonic)(Am2phen)(CO)3]+ 中也观察到了强烈的电荷转移跃迁 MLCTRe→et-isonic 的贡献。与典型的 Re(i) 金属有机配合物相比，用 et-isonic 配体取代 Cl 配体导致发射峰发生红移，发射量子产率相对较低，寿命较短。对 fac-[ReCl(et-isonic)2(CO)3] 化合物的光物理研究为 fac-[Re(L)(Am2phen)(CO)3]0/+ 配合物的激发态能级提供了有意义的信息。如吸收谱所示，最低激发态发生了显著的反转，通常观察到的 MLCTRe→Am2phen 转变为不常见的 MLCTRe→et-isonic。正配合物的亲脂性高于非电荷配合物，并且在没有光照的情况下观察到对细胞的活性也呈现出相同的趋势。此外，流式细胞术和 Western Blot 分析显示，前半胱天冬酶-9 的表达上调，表明通过内在途径凋亡机制发生了半胱天冬酶蛋白酶级联反应。本文报道的这些化合物的光物理性质为理解与实际发展相关的金属有机配合物中配体取代基提供了新的基本见解。
