Quantum chemical DFT study of the interaction between molecular oxygen and FeN4 complexes, and effect of the macrocyclic ligand

Organometallic Nucleosides: Synthesis and Biological Evaluation of Substituted Dicobalt Hexacarbonyl 2'-Deoxy-5-oxopropynyluridines

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.

Synthesis and reactivity of a 4His enzyme model complex

A new iron(II) complex has been prepared and characterized. [Fe(TrIm)4(OTf)2] (1, TrIm = 1-Tritylimidazole). The solid state structure of 1 has been determined by X-ray crystallography. Compound 1 crystallizes in triclinic space group P1̄, with a = 13.342(7) Å, b = 13.5131(7) Å and c = 13.7025(7) Å. The iron center resides in distorted octahedral geometry coordinated to four equatorial imidazole groups and two axial triflate oxygens groups. The complex is high spin between 20 K and 300 K as indicated by variable field variable temperature magnetic measurements. A fit of the magnetic data yielded g = 2.24 and D = -0.80 cm-1. A large HOMO-LUMO gap energy (3.89 eV) exists for 1 indicating high stability. Addition of H2O2 or t BuOOH to 1 results in formation of an oxygenated intermediate which upon decomposition results in oxidation of the trityl substituent on the imidazole ligand.

Assembly of a mononuclear ferrous site using a bulky aldehyde-imidazole ligand

A new iron(II) complex has been prepared and characterized. [Fe(TrImA)2(OTf)2] (1, TrImA = 1-Tritylimidazole-4-carboxaldehyde). The solid state structure of 1 has been determined by X-ray crystallography. Compound 1 crystallizes in monoclinic space group P21/c, with a = 10.8323(18) Å, b = 8.1606(13) Å and c = 24.818(4) Å. The iron center is coordinated to two imidazole groups, two pendant aldehyde-derived carbonyl oxygens and two triflate oxygens. The complex is high spin between 300 and 20 K as indicated by variable field variable temperature magnetic measurements. A fit of the magnetic data yielded g = 2.17 and D = 4.05 cm-1. A large HOMO-LUMO gap energy (4.49 eV) exists for 1 indicating high stability.