Synthesis, photophysical characterisation, quantum-chemical study and in vitro antiproliferative activity of cyclometalated Ir(III) complexes based on 3,5-dimethyl-1-phenyl-1 H -pyrazole and N,N-donor ligands.

In this paper, we present the synthesis of four new complexes: the dimeric precursor [Ir(dmppz) 2 ( μ -Cl)] 2 (1) (Hdmppz - 3,5-dimethyl-1-phenyl-1 H -pyrazole) and heteroleptic bis-cyclometalated complexes: [Ir(dmppz) 2 (Py 2 CO)]PF 6 ·½CH 2 Cl 2 (2), [Ir(dmppz) 2 (H 2 biim)]PF 6 ·H 2 O (3), and [Ir(dmppz) 2 (PyBIm)]PF 6 (4), with auxiliary N,N-donor ligands: 2-di(pyridyl)ketone (Py 2 CO), 2,2'-biimidazole (H 2 biim) and 2-(2'-pyridyl)benzimidazole (PyBIm). In the obtained complexes, SC-X-ray analysis revealed that Ir(III) has an octahedral coordination sphere with chromophores of the type {IrN 2 C 2 Cl 2 } (1) or {IrN 4 C 2 } (2-4). The complexes obtained, which have been fully characterised by physicochemical methods (CHN, TG, FTIR, UV-Vis, PL and 1 H, 13 C, 15 N NMR), were used to continue our studies on the factors influencing the cytotoxic properties of potential chemotherapeutic agents ( in vitro ). To this end, the following studies are presented: (i) comparative analysis of the effects on the biological properties of N,N-donor ligands and C,N-donor ligands in the studied complexes, (ii) studies of the interactions of the compounds with the selected molecular target: DNA and BSA (UV-Vis, CD and PL methods), (iii) and the reactivity towards redox molecules: GSH, NADH (UV-Vis and/or ESI-MS methods), (iv) cytotoxic activity (IC 50 ) of potential chemotherapeutics against MCF-7, K-562 and CCRF-CEM cell lines.