Six new copper(ii) complexes with 2,2':6',2''-terpyridine (4'-R-terpy) [1 (R = furan-2-yl), 2 (R = thiophen-2-yl), and 3 (R = 1-methyl-1H-pyrrol-2-yl)] and 2,6-di(thiazol-2-yl)pyridine derivatives (R-dtpy) [4 (R), 5 (R), and 6 (R)] have been synthesized by a reaction between copper(ii) chloride and the corresponding ligand. The complexes have been characterized by UV-vis and IR spectroscopy, and their structures have been determined by X-ray analysis. The antiproliferative potential of copper(ii) complexes of 2,2':6',2''-terpyridine and 2,6-di(thiazol-2-yl)pyridine derivatives towards human colorectal (HCT116) and ovarian (A2780) carcinoma as well as towards lung (A549) and breast adenocarcinoma (MCF7) cell lines was examined. Complex 1 and complex 6 were found to have the highest antiproliferative effect on A2780 ovarian carcinoma cells, particularly when compared with complex 2, 3 with no antiproliferative effect. The order of cytotoxicity in this cell line is 6 > 1 > 5 > 4 > 2 ≈ 3. Complex 2 seems to be much more specific towards colorectal carcinoma HCT116 and lung adenocarcinoma A549 cells. The viability loss induced by the complexes agrees with Hoechst 33258 staining and typical morphological apoptotic characteristics like chromatin condensation and nuclear fragmentation. The specificity towards different types of cell lines and the low cytotoxic activity towards healthy cells are of particular interest and are a positive feature for further developments. Complexes 1-6 were also tested in the oxidation of alkanes and alcohols with hydrogen peroxide and tert-butyl-hydroperoxide (TBHP). The most active catalyst 4 gave, after 120 min, 0.105 M of cyclohexanol + cyclohexanone after reduction with PPh. This concentration corresponds to a yield of 23% and TON = 210. Oxidation of cis-1,2-dimethylcyclohexane with m-CPBA catalyzed by 4 in the presence of HNO gave a product of a stereoselective reaction (trans/cis = 0.47). Oxidation of secondary alcohols afforded the target ketones in yields up to 98% and TON = 630.

Five monomeric oxovanadium(V) complexes [VO(OMe)(NO)] with the nitro or halogen substituted quinolin-8-olate ligands were synthesized and characterized using Fourier transform infrared, H andC NMR, high-resolution mass spectrometry-electrospray ionization as well as X-ray diffraction and UV-vis spectroscopy. These complexes exhibit high catalytic activity toward oxidation of inert alkanes to alkyl hydroperoxides by HO in aqueous acetonitrile with the yield of oxygenate products up to 39% and turnover number 1780 for 1 h. The experimental kinetic study, the CD and O labeled experiments, and density functional theory (DFT) calculations allowed to propose the reaction mechanism, which includes the formation of HO· radicals as active oxidizing species. The mechanism of the HO· formation appears to be different from those usually accepted for the Fenton or Fenton-like systems. The activation of HO toward homolysis occurs upon simple coordination of hydrogen peroxide to the metal center of the catalyst molecule and does not require the change of the metal oxidation state and formation of the HOO· radical. Such an activation is associated with the redox-active nature of the quinolin-8-olate ligands. The experimentally determined activation energy for the oxidation of cyclohexane with complex [VO(OCH)(5-Cl-quin)] (quin = quinolin-8-olate) is 23 ± 3 kcal/mol correlating well with the estimate obtained from the DFT calculations.

Two gold(iii) complexes incorporating 2,2':6',2''-terpyridine derivatives have been synthesised and characterized, and the possibility of tuning the cytotoxic activity by structural modifications of a terpy ligand has been examined. Both complexes [AuCl(4'-R-terpy)](PF) (1) and [AuCl(4'-R-terpy)](PF) (2), where R is 2-pyridyl and R is 3-pyridyl, show good anti-proliferative activities against HCT116, which are higher in relation to those of the free ligands, [AuCl(terpy)](PF) and standard anticancer drug cisplatin. The cytotoxic properties of the gold complexes were examined by MTS assay, cell cycle and apoptosis analysis, ROS measurements, determination of mitochondrial membrane potential and mass, and staining of phosphatidylserine with Annexin-V antibody FITC-conjugated together with PI.

Structural, spectroscopic and electrochemical properties of six complexes [AuCl(L1)](PF6)2·CH3CN (1), [AuCl(L2)](PF6)2 (2), [PtCl(L1)](BPh4)·CH3CN (3), [PtCl(L2)](SO3CF3) (4), [CuCl2(L1)] (5) and [CuCl2(L2)]·CH3CN (6) with modified 2,2':6',2''-terpyridine ligands, 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine (L1) and 4'-(4-methoxynaphthalen-1-yl)-2,2':6',2''-terpyridine (L2) were thoroughly investigated and a significant role of the substituent (4-methoxyphenyl or 4-methoxynaphthalen-1-yl) and the metal center was demonstrated. The naphthyl-based substituent was found to increase the emission quantum yield of the luminescent Au(iii) and Pt(ii) complexes. Furthermore, the antiproliferative potential of the reported complexes was examined towards human colorectal (HCT116) and ovarian (A2780) carcinoma cell lines as well as towards normal human fibroblasts. The Au(iii) complex 2 and Cu(ii) complex 5 were found to have a higher antiproliferative effect on HCT116 colorectal and A2780 ovarian carcinoma cells when compared with the Pt(ii) complex with the same ligand (4). The order of cytotoxicity in both cell lines is 2 > 6 > 1 > 3 > 4. Complex 2 seems to be more cytotoxic towards HCT116 and A2780 cancer cell lines with IC50 values 300× and 130× higher in normal human fibroblasts compared to the respective cancer cells. The viability loss induced by the complexes agrees with Hoechst 33258 staining and the typical morphological apoptotic characteristics like chromatin condensation and nuclear fragmentation and flow cytometry assay. The induction of apoptosis correlates with the induction of reactive oxygen species (ROS). Fluorescence microscopy analysis indicates that after 3 h of incubation, complexes 1-4 are localized inside HCT116 cells and the high levels of internalization correlate with their cytotoxicity.

Nine rhenium(i) complexes possessing three carbonyl groups together with a bidentate coordinated 2,6-di(thiazol-2-yl)pyridine derivative were synthesized to examine the impact of structure modification of the triimine ligand on the photophysical, thermal and electrochemical properties of [ReCl(CO)(4-R-dtpy-κN)]. The Re(i) complexes were fully characterized using IR, H andC, HRMS-ESI and single crystal X-ray analysis. Their thermal properties were evaluated using DSC and TGA measurements. Photoluminescence spectra of [ReCl(CO)(4-R-dtpy-κN)] were investigated in solution and in the solid state, at 298 and 77 K. Both emission wavelengths and quantum yields of [ReCl(CO)(4-R-dtpy-κN)] were found to be structure-related, demonstrating a crucial role of the substituent attached to the 2,6-di(thiazol-2-yl)pyridine skeleton. In order to fully understand the photophysical properties of [ReCl(CO)(4-R-dtpy-κN)], density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed. Furthermore, the complexes which showed appropriate solubility in chloroform were tested as an emissive active layer in OLED devices.