Ruthenium Complexes of Rigid, Dianionic, Tetradentate N‐Donor Ligands and their Potential as Catalysts for Water Oxidation

Abstract

Two mononuclear ruthenium(II) complexes based on dianionic {N4} ligands and with axial pyridines have been prepared and characterized crystallographically (1) or by 2D NMR spectroscopy using residual dipolar couplings (2). The {N4} ligands provide a constrained equatorial coordination with one large N−Ru−N angle, and additional non‐coordinating N atoms in case of 2. Their redox properties have been investigated (spectro)electrochemically, and their potential to serve as water oxidation catalysts has been probed using cerium ammonium nitrate (CAN) at pH 1.0. Complex 1 undergoes rapid degradation, likely via ligand oxidation, whereas 2 is more rugged and exhibits 80 % efficiency in the CeIV‐driven water oxidation, with a high initial turnover frequency (TOFi) of 3.07×10−2 s−1 (at 100 equiv. CAN). The initial rate of O2 evolution exhibits 1st order dependence on catalyst concentration, suggesting a water nucleophilic attack mechanism. Repeated addition of CAN and control experiments show that high ionic strength conditions (both NO3− and CeIII) significantly decrease the TOF.

Complexes of Ruthenium(II) as Promising Dual-Active Agents against Cancer and Viral Infections

“…Recently, de Araujo-Neto et al (2023) [145] presented the in vitro and in vivo studies of half-sandwich Ru complexes (20)(21)(22) with alizarin, specifically Ru/arene/alizarin, as antitumor agents. The cell lines used in their in vitro assays were MDA-MB-231 and MCF-7 breast cancer cell lines and A549 lung tumor cell lines against the nontumor cell lines MCF-10A and MRC-5, respectively.…”

“…Among the precious metals, ruthenium (Ru) has singular physicochemical properties, which makes it particularly useful in drug design [19]. Ru complexes represent an important class of metallo-organic compounds with numerous applications, and they are currently used in the fields of catalysis [20][21][22][23], including homogeneous, heterogeneous, and photocatalysis [24]. Moreover, numerous biological activities, such as antifungal [25], antibacterial [26], and anticarcinogenic [27][28][29][30][31][32], have been described for the complexes of Ru, as well as their uses in neurodegenerative diseases [33].…”