Emissive luminescent, redox-active Ru(II) bischlorido(triphenylphosphine) complexes containing functionalized imidazole tethered thiourea and dithiocarbamate: characterization and preliminary anticancer quantum chemical calculations

• The [RuCl 2 (PPh 3 )(dtu)(mza) (OH)]: ( Y1 ) and [RuCl 2 (PPh 3 )(pex)(mza)]: ( ZD2 ) possess strong absorption and emission properties and stable in DMSO solvent. • Ligand choice affects both the photophysical, electrochemical and biological activities. • Complexes Y1 and ZD2 exhibit strong inhibitory constants and binding affinities against ERα+ (8DU6) and hFR-β (4KMZ) at (–160.749; –142.242 and –144.164; –157.592) respectively. • Complexes Y1 and ZD2 may act as new potential bioactive agents with better photostability and high selectivity in applications such as bioimaging and/or optical biosensors. The current paper reports the experimental, photophysical, electrochemical characterization and a preliminary quantum chemical studies evaluation of anti-cancer potential of two mixed-ligand heteroleptic ruthenium(II) complexes containing monodentate 4-imidazoleacrylic acid and bischlorido(triphenylphosphine) tethered with either thiourea or dithiocarbamate moiety obtained in a one-pot reaction synthesis. The complexes formulated as [RuCl 2 (PPh 3 )(dtu)(mza) (OH)]: (Y1) and [RuCl 2 (PPh 3 )(pex)(mza)]: (ZD2), with (dtu = thiourea, mza = 4-imidazole acrylic acid and pex = dithiocarbamate) were characterized by elemental analysis, FT-IR, UV-Vis, PL, 1 H, 13 C, 31 P NMR and MS. The photophysical properties of the two complexes showed appreciable absorption bands at the UV-Vis absorption region wavelengths λ max at (284, 373 nm) and weak absorption maxima at 508 and 638 nm indicative of the presence of π→π*, LLCT and MLTC charge transitions. High intensive photoluminescent emission bands are recorded for both complexes Y1 and ZD2 at λ em 554 and 590 nm respectively, although with Y1 having better luminescent quantum yield (0.71) than ZD2 (0.36) at a common excitation energy. A rapid electrochemical screening study using cyclic voltammogram supported by square-wave voltammogram revealed stronger redox activity negative potential (V) for ZD2 than Y1. Despite the close similarity in chemical structures of the two complexes, the molecular docking/DFT reports showed strong inhibitory constants and binding affinities of complexes Y1 and ZD2 against ERα+ (8DU6) and hFR-β (4KMZ) at –160.749; –142.242 and –144.164; –157.592 respectively when compared to Abemaciclib, being the standard drug at –148.104; –181.067. This work provides firsthand preliminary information on target opportunities aimed at finding new potential bioactive agents with better photostability and high selectivity that could be employed for bioimaging, optical biosensors and/or other emerging applications based on thiourea, dithiocarbamate and 4-imidazoleacrylic acid moieties. Ruthenium(II) complexes particularly those containing thiourea, dithiocarbamate, triphenylphosphine and imidazole derivatives have shown to be rare class of compounds with high bioactivity properties and in the treatment of varied forms of cancer or as antitumor agents. This paper particularly reports the photophysical, electrochemical characteristics and the preliminary quantum chemical calculations (molecular docking) that gave insights into intrinsic anti-cancer properties of two newly prepared ruthenium(II) metal complexes containing bischlorido(triphenylphosphine), 4-imidazoleacrylic acid tethered with thiourea, dithiocarbamate ligands. A structure activity relationship in the two complexes including the presence of carboxylic acid functionality could play major significant roles if tested for DNA protein binding of new drugs and/or for other emerging biological applications.