N. Mincheva

Bio: N. Mincheva is an academic researcher. The author has contributed to research in topics: Bridging ligand & Ligand. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

Synthesis of New Monomeric Pd(III) and Dimeric (Pd(III),Pd(II)) Complexes with Biuret Formed in Basic Medium

Abstract: New monomeric Pd(III) and dimeric (Pd(III)-Pd(II)) paramagnetic complexes with biuret (BiuH2) were synthesized and their structures and coordination modes studied using magnetochemical and spectroscopic (EPR, IR, ESCA) methods. For the monomeric species a metal to ligand ratio 1:2 was found and for the dimeric one it was 2:3. A distorted rhombic structure was suggested for the [Pd(III)(Biu)2]− species. For the dimeric complex it was accepted that one of the biuret molecules is serving as bridging ligand coordinated via both NH-groups to one of the palladium ions and via both C=O groups to the other. A distorted rhombic structure is suggested for each of the palladium ions. Referee I: W. A. Donaldson Referee II: N. M. Kostic

Structural and spectroscopic comparisons of the square-planar four-coordinate [o-phenylenebis(biuretato)]cobaltate(III) complex and the five-coordinate mono- and six-coordinate dicyano adducts

Abstract: The addition of cyanide ion to the paramagnetic four-coordinate square-planar cobalt(III) complex, [Co(bbphen)]− {H4bbphen = o-phenylenebis(biuret), [1]−}, afforded the diamagnetic mono- and dicyano complexes [Co(bbphen)(CN)]2− ([2]2−) and [Co(bbphen)(CN)2]3− ([3]3−). The X-ray crystal structure analyses of [K(crypt)][1] (crypt = cryptand[2,2,2]), (PPh4)2[2]·2CH3CN·H2O, and K3[3]·5.5H2O show them to be a four-coordinate square plane, a five-coordinate square pyramid and a six-coordinate octahedron, respectively. The four-coordinate N atoms of the bbphen ligand in the three complexes were located in a basal plane around the central cobalt atom. The average Co–N bond lengths become longer with increasing coordination number. A novel interactive contact between one of the potassium ions and both the cyano ligand and the phenyl ring of the bbphen ligand is found in K3[3]·5.5H2O. Complex [2]2− exhibits characteristic intense CT absorption bands at 14.0 × 103 (e = 1380) and 22.7 × 103 cm−1 (e = 1480 dm3 mol−1 cm−1) together with the distinctively high field 13C NMR chemical shift of the coordinated cyanide ion at 81.5 ppm, as compared with 143.0 ppm for [3]3− in DMSO.

Cellular Pharmacology of Palladinum(III) Hematoporphyrin IX Complexes: Solution Stability, Antineoplastic and Apoptogenic Activity, DNA Binding, and Processing of DNA-Adducts

Abstract: Two paramagnetic PdIII complexes of hematoporphyrin IX ((7,12-bis(1-hydroxyethyl)-3,8,13,17-tetramethyl-21H-23H-porphyn-2,18-dipropionic acid), Hp), namely a dinuclear one [PdIII2(Hp-3H)Cl3(H2O)5]·2PdCl2, Pd1 and a mononuclear metalloporphyrin type [PdIII(Hp-2H)Cl(H2O)]·H2O, Pd2 have been synthesized reproducibly and isolated as neutral compounds at different reaction conditions. Their structure and solution stability have been assayed by UV/Vis and EPR spectroscopy. The compounds researched have shown in vitro cell growth inhibitory effects at micromolar concentration against a panel of human tumor cell lines. A DNA fragmentation test in the HL-60 cell line has indicated that Pd1 causes comparable proapoptotic effects with regard to cisplatin but at substantially higher concentrations. Pd1 and cisplatin form intra-strand guanine bis-adducts as the palladium complex is less capable of forming DNA adducts. This demonstrates its cisplatin-dissimilar pharmacological profile. The test for efficient removal of DNA-adducts by the NER synthesis after modification of pBS plasmids with either cisplatin or Pd1 has manifested that the lesions induced by cisplatin are far better recognized and repaired compared those of Pd1. The study on the recognition and binding of the HMGB-1 protein to cisplatin or Pd1 modified DNA probes have shown that HMG proteins are less involved in the palladium agent cytotoxicity.