An experimental and quantum chemical study on the non-covalent interactions of a cyclometallated Rh(iii) complex with DNA and BSA

Abstract

The interaction of a new cyclometallated Rh(III) complex, [Rh(phpy-κ²N,C^2′)₂(dafone)]⁺ (phpy-κ²N,C^2′ = pyridine-2-yl-2-phenyl and dafone = 4,5-diazafluoren-9-one), with DNA and BSA was investigated. The in vitro cytotoxicity tests of the complex against three cancer cell lines demonstrate that the complex can be introduced as an efficient anticancer agent. The binding of the complex to DNA and BSA was modeled by molecular docking. The three-layer ONIOM method (QM:QM:MM) was employed to calculate the interaction energy between DNA and the complex, where QM and MM are abbreviations of quantum mechanics and molecular mechanics, respectively. The complex and a part of the DNA were considered in the QM region at the same theoretical level, whereas the different basis sets for DNA, the complex, and the rest of system were considered in the MM region. Density functional theory (DFT) employing the M062X functional was used for the QM parts of the system. The M062X functional is one the best DFT functionals, introduced in recent years, which considers non-covalent interactions properly. The UV spectra of the complex interacting with DNA in the gas phase and water were calculated using the two- and three-layer ONIOM methods employing time-dependent density functional theory (TD-DFT) to investigate the effect of the interaction on the electronic structure of the complex. The calculations interestingly confirm the variations observed in the recorded spectra of the complex due to its interaction with DNA.