Functional Pt(II) and Re(I) Complexes with CO- and β-Carboline-Based Coligands: From Time-Resolved Photoluminescence Spectroscopy and Evaluation of 1O2 Photosensitization Efficiency toward in vitro (Photo)cytotoxicity

Abstract

In this study, the synthesis, photophysical characterization, and (photo)biological assessment of functional rhenium(I)- and platinum(II)-based complexes are presented. These compounds feature anionic 1,2,4-triazolylpyridine-based chromophores and neutral βC-based monodentate coligands, specifically 9H-pyrido[3,4-b]indole (nHo) or 9-methyl-9H-pyrido[3,4-b]indole (MenHo), which have been chosen to promote their biological activity. The impact of transition metal cations, coordination geometries, substitution patterns of the luminophore and coligands on the properties of these complexes was thoroughly assessed, encompassing photoluminescence and singlet dioxygen (1O2) quantum yields, excited state lifetimes, and (non)radiative rate constants, across various temperatures and phases. Superior photophysical characteristics were attained by the Pt(II)-based complexes, while effective capabilities as photosensitizers of 1O2 were observed for all coordination compounds. Incorporation of these complexes into a polymeric matrix (PMMA) significantly enhanced their luminescence efficiencies by preventing diffusional quenching arising from triplet dioxygen (3O2). Furthermore, a comprehensive (photo)cytotoxicity study on human telomerase reverse transcriptase (hTERT)-immortalized cells was conducted to assess the potential applications of these complexes in photodynamic therapy. In summary, a versatile platform for designing photofunctional materials with photosensitizing properties is offered by this coordination chemical approach. Precise control of photophysical and (photo)biological attributes is achievable through the careful selection of metal centers, substitution patterns, and ancillary ligands.