Understanding the photophysical properties of rhenium(I) compounds coordinated to 4,7-diamine-1,10-phenanthroline: synthetic, luminescence and biological studies

Author(s)

Ramos, Luiz D. ^[1] ; de Macedo, Leonardo H. ^[1] ; Gobo, Nicholas R. S. ^[2] ; de Oliveira, Kleber T. ^[2] ; Cerchiaro, Giselle ^[1] ; Morelli Frin, Karina P. ^[1]

Affiliation

^[1] Fed Univ ABC UFABC, Av Estados 5001, Santo Andre, SP - Brazil

^[2] Univ Fed Sao Carlos, Rodovia Washington Luis, Km 235, Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: DALTON TRANSACTIONS; v. 49, n. 45, p. 16154-16165, DEC 7 2020.
• Web of Science Citations: 0

Abstract

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)(Am(2)phen)(CO)(3)](0/+), where Am(2)phen = 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 IL(Am2)phen and MLCTRe -> Am2phen transitions, and a strong contribution of charge transfer transition MLCTRe -> et-isonic for fac-{[}Re(et-isonic)(Am(2)phen)(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)(Am(2)phen)(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. (AU)

• FAPESP's process: 18/14152-0 - Studies for Prion Protein Cellular and metallic ions in oxidative stress
• Grantee: Giselle Cerchiaro
• Support type: Regular Research Grants
• FAPESP's process: 18/00106-7 - Photocatalyzed Reactions by using porphyrins and continuous flow conditions: Arylations of heterocycles and activated olefins.
• Grantee: Kleber Thiago de Oliveira
• Support type: Regular Research Grants
• FAPESP's process: 17/18063-0 - Evaluation of Re(I) luminescent compounds in bio-imaging and/or antitumor agents
• Grantee: Karina Passalacqua Morelli Frin
• Support type: Regular Research Grants
• FAPESP's process: 16/09652-9 - Biomolecule damage in neural cellular system in metalic and redox inbalance
• Grantee: Giselle Cerchiaro
• Support type: Regular Research Grants