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

Abstract

In this paper, we present the synthesis of four new complexes: dimeric precursor [Ir(dmppz)₂(μ-Cl)]₂ (1) (Hdmppz - 3,5-dimethyl-1-phenyl-1H-pyrazole) and heteroleptic bis-cyclometalated complexes: [Ir(dmppz)₂(Py₂CO)]PF₆ · ½ CH₂Cl₂ (2), [Ir(dmppz)₂(H₂biim)]PF₆ · H₂O (3), [Ir(dmppz)₂(PyBIm)]PF₆ (4), with auxiliary N,N-donor ligands: 2-di(pyridyl)ketone (Py₂CO), 2,2’-biimidazole (H₂biim) 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 {IrN₂C₂Cl₂} (1) or {IrN₄C₂} (2-4). The complexes obtained, which have been fully characterised by physicochemical methods (CHN, TG, FTIR, UV-Vis, PL and ¹H, ¹³C, ¹⁵N 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 (IC50) of potential chemotherapeutics against MCF-7, K-562 and CCRF-CEM cell lines