A novel Rh^III complex containing a pincer type nitrogen-donor ligand was synthesized; its interaction toward small biomolecules, duplex DNAs and RNA as well as CT-DNA and BSA was investigated.

The synthesis and structural characterization of a newly synthesized mononuclear rhodium(III) complex, Rhtrz, with a ligand (2,2,6-bis((4S,7R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-1H-4,7-methanoindazol-3-yl)pyridine) and a ligand of 1,2,4-triazole, are presented in this paper. The kinetic interactions of the Rhtrz complex with essential biomolecules such as 5-GMP, L-Met, and GSH were examined. The study of the biological interactions was focused on the binding properties of the Rhtrz complex with CT-DNA and serum albumin. These interactions were investigated using UV-vis spectrophotometry, fluorescence spectroscopy, viscosity measurements, thermal denaturation studies, and electrophoresis. Fluorescence competition experiments with site-markers for BSA were used to locate the binding site of the Rhtrz-complex to the BSA. Molecular docking studies were carried out to obtain detailed binding information of the complex with CT-DNA, BSA, and HSA. Furthermore, the apparent distance between the donor (HSA) and acceptor (Rhtrz) was determined using fluorescence resonance energy transfer (FRET). The thermodynamic properties and relative stabilities of the Rhtrz complex were examined, constructing the two model equation by DFT calculations (B3LYP(CPCM)/LANL2DZp). In vitro cytotoxicity and redox status on the human epithelial colorectal cancer cell line (HCT-116) and healthy human fibroblast cell line (MRC-5) were also investigated.

Within this paper is presented the synthesis and structural characterization of three newly synthesized osmium(II) complexes Os1–3, with the chemical formula [Os^IILCl₂H₂O], [L = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine (for Os1), 2,6-bis(5-tert-butyl-1-methyl-1H-pyrazol-3-yl)pyridine (for Os2) or 2,2′:6′,2′′-terpyridine (for Os3)]. Single crystal X-ray analysis of a DMSO adduct of complex Os1 was performed. Kinetics of substitution reactions of examined Os1–3 complexes with biomolecules 5-GMP, L-Met, and GSH were followed in the presence and absence of different biocompatible ionic liquids. Binding properties of the examined complexes to biologically important molecules, CT-DNA and HSA, were investigated using UV-Vis spectrophotometry, fluorescence spectroscopy, and gel electrophoresis. Interactions with CT-DNA were performed both in the absence and presence of biocompatible ionic liquids. To locate the binding site and possible binding mode of the examined complexes to CT-DNA and HSA, fluorescence competition experiments with site-markers were performed. To better understand these interactions and obtain detailed binding information of the examined complexes with CT-DNA, and HSA, molecular docking studies and fluorescence resonance energy transfer (FRET) were performed. In vitro cytotoxicity and redox status experiments on three cancer cell lines and on one healthy cell line were performed to elucidate the possible molecular mechanisms of investigated Os1–3 complexes.

Two new Pt(II) complexes with imidazolin-2-imines as ancillary ligands, [Pt(DMEAIm^iPr)Cl₂] and [Pt(DPENIm^iPr)Cl₂], were synthesized and characterized. Substitution reactions of these complexes with nucleophiles – thiourea (TU), L-methionine (L-Met), L-histidine (L-His) and guanosine-5′-monophosphate (5′-GMP) – were carried out in 25 mM Hepes buffer in the presence of 30 mM NaCl. The reactions were monitored using variable-temperature UV-Vis spectrophotometry and were followed under pseudo-first-order conditions with a large excess of nucleophiles. A slightly higher reactivity was found for [Pt(DMEAIm^iPr)Cl₂], while the reactivity of the nucleophiles decreased in the order TU > L-Met > L-His > 5′-GMP. The negative values reported for the entropy of activation confirmed an associative substitution mode. Spectrophotometric acid–base titrations were performed to determine the pK_a values of the coordinated water molecules in the diaqua complexes [Pt(DMEAIm^iPr)(H₂O)₂]²⁺ and [Pt(DPENIm^iPr)(H₂O)₂]²⁺. Solubility measurements revealed good solubility of the studied imidazolin-2-imine complexes in water. The crystal structure of [Pt(DMEAIm^iPr)Cl₂] was determined by X-ray diffraction analysis. The coordination geometries around the platinum atoms are distorted square-planar; the [Pt(DMEAIm^iPr)Cl₂] complex displays Pt–N distances of 2.0162(19) and 2.0663(19) Å. Attempts to coordinate Au(III) ions to different imidazolin-2-imine ligands did not result in the formation of coordination complexes, but rather in the reduction of the Au(III) precursor. This was evidenced by the X-ray crystal structure of [(DACH(Im^iPrH)₂)(AuCl₂)₂], which formed during the reaction of KAuCl₄ with the ligand DACH(Im^iPr)₂.