Reactions of dicobalt octacarbonyl [Co₂(CO)₈] with 2′‐deoxy‐5‐oxopropynyluridines and related compounds gave dicobalt hexacarbonyl nucleoside complexes (83–31 %). The synthetic outcomes were confirmed by X‐ray structure determination of dicobalt hexacarbonyl 2′‐deoxy‐5‐(4‐hydroxybut‐1‐yn‐1‐yl)uridine, which exhibits intermolecular hydrogen bonding between a modified base and ribose. The electronic structure of this compound was characterized by the DFT calculations. The growth inhibition of HeLa and K562 cancer cell lines by organometallic nucleosides was examined and compared to that by alkynyl nucleoside precursors. Coordination of the dicobalt carbonyl moiety to the 2′‐deoxy‐5‐alkynyluridines led to a significant increase in the cytotoxic potency. The cobalt compounds displayed antiproliferative activities with median inhibitory values (IC₅₀) in the range of 20 to 80 μm for the HeLa cell line and 18 to 30 μm for the K562 cell line. Coordination of an acetyl‐substituted cobalt nucleoside was expanded by using the 1,1‐bis(diphenylphosphino)methane (dppm) ligand, which exhibited cytotoxicity at comparable levels. The formation of reactive oxygen species in the presence of cobalt compounds was determined in K562 cells. The results indicate that the mechanism of action for most antiproliferative cobalt compounds may be related to the induction of oxidative stress.

The synthesis, chromatographic isolation, and structure elucidation of β,β-substituted isomers of dinitro-5,10,15,20-tetraphenylporphyrin complexes are described. meso-Tetraphenyl-porphyrin chelates (Cu^II, Ni^II, Co^II) upon reaction wit e.g., nitric acid (yellow HNO₃, d = 1.52, diluted to 25–50%) in CHCl₃ formed a mixture of nitro-derivatives with combined yields of ca 80%. This nitration (under optimized conditions: 25–30% HNO₃, 30–40 min, r.t.) can be carried out selectively to give mainly β,β-dinitro-compounds in yields of up to 73%. From the above mixtures of five possible regioisomers that can be formed, usually two or three of them were isolated, for which the structures were assigned on the basis of ¹H NMR spectra including COSY and NOESY measure-ments. These types of products are attractive starting materials for synthesis of potential anticancer PDT agents with unique structures, being practically unavailable by any other alternative method.