G. Gencheva

Abstract: Pt(II) and Pd(II) complexes with creatinine, C3H2N2(O)(CH3)NH2, were synthesized. Potentiometric and IR spectroscopic analyses were carried out. A model for the coordination of the ligands to the central atoms was confirmed by X-ray structural investigation of Pt(creat)4(ClO4)2. The compound [Pt(C4H7N3O)(ClO4)2] crystallizes in the monoclinic crystal system, space group C2/c, a = 15.748(5), b = 15.763(7), c = 24.843(8) A, β = 106.84(4)°, V = 5902 A3, Z = 8. The refinement of the structure by the least-squares method gave R = 0.051 and Rw = 0.054 for 1527 observed reflections with I > 2σ(I). The structure consists of Pt(creat)42+ complex cations, possessing approximate D2 symmetry and rotationally disordered perchlorate anions. The Pt atom is square-planarly coordinated by the endocyclic N atoms of four creatinine ligands. The PtN bond lengths range from 2.00(2) to 2.03(1) A and the NPtN angles from 88.4(9) to 91.8(8)°. The ligands are almost planar and tilted towards the PtN4-plane by 82.1(8)–93.5(9)°.

Abstract: Three different types of Ni(II)-creatinine complexes are synthesized in organic media. It was proved that the complexes are formed only in non-aqueous media and their dissolution in water is connected with immediate dissociation. The three complexes were studied using spectroscopic (IR, EPR, ESCA) magnetochemical and thermogravimetric methods. An octahedral structure and different contents of creatinine molecules in their inner coordination spheres were assumed.

Abstract: A new platinum complex with creatinine [C3H2 N2(O)(CH3)NH2] exhibiting paramagnetic properties was synthesized fully characterized by crystallographic, spectral magnetic measurements. The compound [AsPh4]+[Pt(creatinine)Cl3]− crystallizes to give a columnar honeycomb motif of tetraphenylarsonium cations with the channels occupied by creatinine anions. The shortest Pt-Pt distance is 7.622(1). A remarkable feature of the structure is the formation of short Ptμ H intermolecular bonds of 2.73(2) A. The temperature dependence of both μeff and EPR parameters of the complex has been studied.

Abstract: A stable monomeric Au(II) complex has been synthesized in the course of the Au(III)–hematoporphyrin IX (Hp, I) interaction in aqueous alkaline solution. Distorted octahedral structure with (dxy)1 ground state and general formula Au(II)Hp-2H·2H2O are suggested for the complex. Gold is located in the hole of the porphyrin macrocycle and the water molecules are in axial position. The +2 oxidation state of gold was proven by the corresponding EPR signal and the μeff value of 2.20 BM obtained. The α2 value of 0.56 indicated a high degree of covalency of the gold–nitrogen bonds.

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

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: Platinum compounds represent one of the great success stories of metals in medicine. Following the serendipitous discovery of the anticancer activity of cisplatin by Rosenberg, a large number of cisplatin variants have been prepared and tested for their ability to kill cancer cells and inhibit tumor growth. These efforts continue today with increased realization that new strategies are needed to overcome issues of toxicity and resistance inherent to treatment by the approved platinum anticancer agents. One approach has been the use of so-called “non-traditional” platinum(II) and platinum(IV) compounds that violate the structure–activity relationships that governed platinum drug-development research for many years. Another is the use of specialized drug-delivery strategies. Here we describe recent developments from our laboratory involving monofunctional platinum(II) complexes together with a historical account of the manner by which we came to investigate these compounds and their relationship to previous...

Abstract: The discovery of cisplatin (cis-Pt(NH3)2Cl2) as an antineoplastic agent has focussed attention on the rational design of metal complexes that can be potentially used in cancer chemotherapy. Today, the pharmaceutical industry invests more than $1 billion each year in the development of new metal-based drugs to improve biological activities, in terms of cellular selectivity, therapeutic efficiency and minimization of side effects. Chemotherapies based on transition metals play a key role in cancer treatment, and among them platinum and palladium are the most fruitful. This article reviews the main recent advances in the design and synthesis of platinum- and palladium-based drugs, their structural features and biological studies of them. The rationale for the choice of the ligand, related to leaving groups, the geometry of the complex and the oxidation state of the metal ion, is discussed. An overview of the main biological techniques and approaches for testing the interaction of these molecules with the biological environment, mainly DNA, to validate the effect is also provided.

Abstract: Pt-doped mesoporous Ti3+ self-doped TiO2 (Pt–Ti3+/TiO2) is in situ synthesized via an ionothermal route, by treating metallic Ti in an ionic liquid containing LiOAc, HOAc, and a H2PtCl6 aqueous solution under mild ionothermal conditions. Such Ti3+-enriched environment, as well as oxygen vacancies, is proven to be effective for allowing the in situ reduction of Pt4+ ions uniformly located in the framework of the TiO2 bulk. The photocatalytic H2 evolution of Pt–Ti3+/TiO2 is significantly higher than that of the photoreduced Pt loaded on the original TiO2 and commercial P25. Such greatly enhanced activity is due to the various valence states of Pt (Ptn+, n = 0, 2, or 3), forming Pt–O bonds embedded in the framework of TiO2 and ultrafine Pt metal nanoparticles on the surface of TiO2. Such Ptn+–O bonds could act as the bridges for facilitating the photogenerated electron transfer from the bulk to the surface of TiO2 with a higher electron carrier density (3.11 × 1020 cm–3), about 2.5 times that (1.25 × 1020 cm...