Mariana Mitewa

Abstract: Mecanisme de formation des complexes de Cr(V). Structure et liaison. Photochimie de la reduction de Cr(VI)

Abstract: Mononuclear neutral manganese(II) and cobalt(II) complexes with the antibiotic Sodium Monensin A (Mon-Na, 1b ) were synthesized and characterized. The crystal structures of M(Mon-Na) 2 Cl 2 · H 2 O (M = Mn, 2 ; M = Co, 3 ) were determined by X-ray crystallography. The complexes crystallize in monoclinic space group C2 with a tetrahedrally coordinated transition metal attached to oxygen atoms of deprotonated carboxyl groups of two Sodium Monensin molecules and two chloride ions. The sodium ion remains in the cavity of the ligand and cannot be replaced by Mn(II) or Co(II). The complexes were additionally characterized by different spectroscopic techniques (UV–Visible, EPR, FAB-MS). A preferable octahedral environment around the transition metal centers is observed in polar solvents while the complexes retain their tetrahedral structure in non-polar media. The antimicrobial activity of 1b , 2 and 3 was tested against Gram(+) and Gram(−) bacteria.

Abstract: Mononuclear Au(III) complexes of the peptides H-His-Met-OH (D) and H-Gly-Gly-Met-OH (T) and their N-protected forms Ac-His-Met-OH (Ac-D) and Ac-Gly-Gly-Met-OH (Ac-T) were structurally characterized by means of IR, MS and NMR. In the complexes with dipeptides [AuLCl2]Cl (L = D or Ac-D), Au(III) is coordinated through S and imidazole N atoms from methionine and histidine fragments of the ligands forming macrochelate rings at mol ratio Au : L = 1 : 1. Additionally, Au(III) is coordinated by two terminal chloride ions in a square-planar arrangement. In complexes with the tripeptides [AuL′Cl] (L′ = T or Ac-T), however, the metal ion is coordinated in a tridentate fashion, through S and two N atoms, also at mol ratio M : L = 1 : 1. The fourth position of Au(III) is occupied by a Cl− ligand.

Abstract: The pulsed laser photolysis (excimer laser, XeCl; 308 nm) of the PtCl 6 2− —creatinine—methanol system was studied. The formation of an intermediate Pt III species (PtCl 5 2− cr, where cr = creatinine) was demonstrated and its decay kinetics were examined. Some kinetic and thermodynamic data of the photoinduced reaction were determined. The photolysis of the same system using stationary irradiation was also investigated allowing the end product of the reaction to be determined.

Abstract: Data on the ability of the important bioligands creatinine and creatine to form various types of complexes with different metal ions are summarized. The crucial role of the nature of the reaction medium in complex formation with these ligands is emphasized. The conditions for obtaining paramagnetic oligomeric platinum complexes of the “platinum blue” type (resulting from multistep redox and coordination processes) are presented.

Abstract: Metal complexes have shown interesting preclinical and clinical results as antitumor drugs and platinum compounds are well established in current cancer chemotherapy However, the platinum based treatment of tumoral diseases is massively hampered by severe side effects and resistance development Consequently, the development of novel metallodrugs with a pharmacological profile different from that of the platinum drugs is in the focus of modern medicinal chemistry and drug design Among the non-platinum antitumor drugs, gold complexes have recently gained considerable attention due to their strong antiproliferative potency In many cases the cell growth inhibiting effects could be related to anti-mitochondrial effects making gold species interesting drug candidates with a mode of action different from that of the platinum agents The spectrum of gold complexes described as antiproliferative compounds comprises a broad variety of different species including many phosphine complexes as well as gold in different oxidation states This presentation gives an overview of the relevant medicinal chemistry of known gold complexes with in vitro and in vivo tumor growth inhibiting properties

Abstract: Real-time and real-space analysis of heavy and transition metal ions employing fluorescent sensor molecules has received much attention over the past few years. Since many of these cations possess intrinsic properties that usually quench the fluorescence of organic dye molecules, a lot of research has lately been devoted to designing fluorescent probes that show complexation-induced fluorescence enhancement. Such an analytical reaction would be highly desirable in terms of increased sensitivity and selectivity. However, in this particular field of sensor research, the photophysical and photochemical mechanisms involved as well as the chemical constitutions of the sensor molecules employed are rather diverse and up to now, very few attempts have been made to establish some general concepts for rational probe design. By analyzing various systems published by other researchers as well as own work, this contribution aims at an elucidation of some of the underlying principles of heavy and transition metal ion-enhanced emission.

Abstract: Species containing the Y-shaped CN3 unit have recently attracted increasing attention as electronically and sterically flexible ligands. Neutral guanidines [(R2N)2CNR], guanidinates(−1) [(RN)2CNR2]− and guanidinates(2) [(RN)2CNR]2− are capable of exhibiting a variety of coordination modes and a range of donor properties leading to compatibility with a remarkably wide range of metal ions from all parts of the periodic table. The coordination chemistry of these species is reviewed up to July 2000, and aspects of their electronic structures and metal-ligand bonding characteristics discussed.