In the first research, a ruthenium(II) complex with mono-anionic Hmel – ligand, trans -[Ru(Hmel) 2 (DMSO) 2 ], was synthesized and characterized. The DNA- and BSA-binding properties of the mono-anionic meloxicam (Hmel – ) ligand and its Ru(II) complex were investigated under physiological conditions. The interaction of the Hmel – ligand and the Ru(II) complex with fish sperm DNA were explored through UV–Vis spectroscopy, emission titration, and viscosity measurement. The results reveal that the mono-anionic Hmel – ligand binds to DNA through intercalation, while the complex interacts with DNA through electrostatic or/and groove binding modes. The complex has stronger tendency to bind with DNA than the free Hmel – ligand. In addition, the binding of them to bovine serum albumin (BSA) was monitored by UV–Vis and fluorescence emission spectroscopy. By the interaction of the BSA with the Hmel – ligand and the Ru(II) complex, the microenvironment of the three aromatic acid residues is altered and the ? -helix of protein is perturb. The in vitro cytotoxicity tests of Hmel – and trans -[Ru(Hmel) 2 (DMSO) 2 ] against the various cancer cell lines demonstrate that the Ru(II) complex has more anticancer activity than the Hmel – ligand. Furthermore, the binding of both compounds to DNA and BSA was modeled by molecular docking method. In the second research, the cyclometallated Rh(III) complex, [Rh(phpy- ? 2 N,C 2' ) 2 (dafone)] + (phpy- ? 2 N,C 2' = pyridine-2-yl-2-phenyl and dafone = 4,5-diazafluoren-9-one), was synthesized and characterized by elemental analysis, spectroscopic methods and single crystal X-ray structure analysis. The interaction of the cyclometallated Rh(III) complex with FS-DNA and BSA was investigated. The results indicate that the Rh(III) complex can bind to DNA through groove binding along with minor intercalative binding. To have a more accurate estimation for the interaction of the Rh(III) complex with DNA, two different ONIOM schemes, two-layer (QM/QM) and three-layer (QM/QM/MM), were employed for the calculations in the gas phase and water, respectively. It can be seen that the deformation of the complex structure in the water medium is considerably lower than that in the gas phase. The three-layer ONIOM method (QM/QM/MM) was employed to calculate the interaction energies between DNA and the complex in the gas phase and water. It is seen that the presence of the water molecules decreases the interaction of the complex with DNA compared to the gas phase. In the third research, a new mononuclear rhodium(III) complex, [Rh(bzimpy)Cl 3 ] (bzimpy = 2,6-bis(2-benzimidazolyl)pyridine), was synthesized and characterized. The molecular structure of the complex was confirmed by single-crystal X-ray crystallography. The interaction of the complex with fish sperm DNA (FS-DNA) was investigated by spectroscopic methods and viscosity measurement. The results reveal that the Rh(III) complex interacts with DNA through groove binding mode. In addition, the binding of the Rh(III) complex to bovine serum albumin (BSA) was monitored by UV–Vis and fluorescence emission spectroscopy at different temperatures. The thermodynamic parameters ( ?H 0 , ?S 0 , and ?G 0 ) obtained from the fluorescence spectroscopy data show that van der Waals interactions and hydrogen bonds play a major role in the binding of the Rh(III) complex to BSA. Competitive site marker experiments indicate that the complex is mainly located in the site I of the protein.