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: the 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)]PF₆·½CH₂Cl₂ (2), [Ir(dmppz)₂(H₂biim)]PF₆·H₂O (3), and [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.