Georgi Gochev

Copper(II) interaction and complexation with 1-[2(S)-3-mercapto-3-methylpropionyl]-L-proline (captopril)

The redox processes between copper(II) and captopril, H2L, in a molar ratio 1:2 were studied. Copper(II) is reduced to Cu(I), which forms with the excess of captopril, a yellow complex, reoxidized by oxygen to a green complex CuIIL.H2O. The latter is studied using spectral (UV-Vis, IR), magnetochemical, EPR, DTA, and TGA methods. The coordination sites of the ligand are COO−, CO, and S−. In a solid state the complex exists mainly as a dimer, the bridging realized by the carboxylate group of the ligand. The complex is soluble in pyridine, forming the mononuclear adduct CuCapt(py)3.

Complexes of copper(II) with the β-blocker atenolol

Mono- and binuclear copper(II) complexes with atenolol (HAt) can be obtained, depending on the reaction conditions. The mononuclear violet complex cation has the general formula Cu(HAt)42+ with an elongated octahedral geometry. The two ligands in the equatorial plane are bound in a bidentate fashion through the hydroxyl oxygen and amino nitrogen, while the other two atenolol molecules in axial position are coordinated in a monodentate way. The binuclear green complex Cu2At2Cl2, is neutral, where atenolol acts as a bidentate (O−, NH) bridging ligand. The bridge between the two Cu atoms is realized by the deprotonated oxygen of the alcohol group.

Absolute structure of a new paramagnetic platinum(II)-creatinine complex with a columnar structure

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.

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

EPR studies on bis(diisopropyldithiophosphato)copper(II) magnetically diluted in the corresponding palladium(II) and platinum(II) single crystals and crystal and molecular structure of bis(diisopropyldithiophosphato)palladium(II) host lattice

Abstract The EPR spectra of single-crystal samples of 63Cu[(Pri2O)2PS2]2 magnetically diluted in the corresponding palladium(II) and platinum(II) host lattices were studied at room temperature and eigen-values of the A and g tensors evaluated. The results obtained show that both the samples have approximately axial symmetry (ΔA = Ax - Ay ⪕ 3 G; Δg = gx - gy ⪕ 0.03) with one molecule per unit cell in both host lattices. It is found that gz coincides with Az whereas the angle between gx and Ax (gy and Ay) is 27° and 11° for 63Cu/Pt[(Pri2O)2PS2]2 and 63Cu/Pd[(Pri2O)2PS2]2, respectively. The data about a quadrupole interaction obtained was considered with special attention, because their values are close to the experimental error. In view of this, the possibility for determining Q values from simulated powdered EPR spectra was explored. The results show, however, inapplicability of this approach too. The crystal and molecular structure of bis(diisopropyldithiophosphato)palladium(II) was determined.

EPR Investigations on bis(dithiophosphinato)copper(II) complexes magnetically diluted in the corresponding nickel(II) single crystals and X-ray crystal structure of bis(di-n-propyldithiophosphinato)nickel(II)

Abstract Bis(diethyldithiophosphinato)nickel(II), [(C2H5)2PS2]2Ni and bis(di-n-propyl dithiophosphinato)nickel(II), [(n-C3H7)2PS2]2Ni, single crystals doped with the corresponding copper(II) complexes have been prepared and studied by EPR spectroscopy. The components of the g-tensor, 63Cu hyperfine coupling tensor and 63Cu nuclear quadrupole coupling tensor have been determined. An X-ray crystal structure determination of bis(di-n-propyldithiophosphinato)nickel(II) shows the nickel atom to lie at a centre of symmetry, coordinated by four sulphur atoms at 2.220(4) and 2.230(3) A.

Synthesis, structure and in vitro cytotoxic studies of novel paramagnetic palladium(III) complexes with hematoporphyrin IX.

Two coordination compounds of Pd(III) with hematoporphyrin IX ((7,12-bis(1-hydroxyethyl)-3,8,13,17-tetramethyl-21H-23H-porphyn-2,18-dipropionic acid), Hp), dinuclear [Pd(III)2(Hp-3H)Cl3(H2O)5]·2PdCl2, 1 and mononuclear [Pd(III)(Hp-2H)Cl(H2O)]·H2O, 2 were obtained and structurally characterized in solid state and solution using spectroscopic, thermal and magnetic methods. In the dinuclear complex, 1 one of the Pd(III) ions is coordinated to the deprotanated COO(-) groups from the side chains of the porphyrin ligand and the second Pd(III) ion - to two adjacent pyrrole N-atoms on the top of the porphyrin ring and a Pd(III)-Hp-Pd(III) system was formed. The Pd(III) ion in the mononuclear complex, 2 is incorporated in the porphyrin core. The Pd(III) centers in both complexes have a distorted octahedral coordination filled with additional donor species such as Cl(-) and H2O. The studied compounds showed in vitro cell growth inhibitory effects at micromolar concentration against a panel of human tumor cell lines. A DNA fragmentation assay indicated that the growth inhibitory effects are at least partly mediated by induction of apoptosis.

Synthesis, Structural Characterization, and Cytotoxic Activity of Novel Paramagnetic Platinum Hematoporphyrin IX Complexes: Potent Antitumor Agents

Three novel stable Pt(III) complexes with distorted octahedral structure and (dz2)1 ground state have been obtained in the course of Pt(II)-hematoporphyrin IX ((7,12-bis(1-hydroxyethyl)-3,8,13,17-tetramethyl-21H-23H-porphyn-2,18-dipropionic acid), Hp) interaction in alkaline aqueous medium and aerobic conditions. A redox interaction also takes place together with the complexation process leading to the formation of Pt(III) species and organic radicals. The processes in the reaction system and the structure of the complexes formed cis-[Pt(III)(NH3)2(Hp−3H)(H2O)2]⋅H2O 1, [Pt(III)(Hp−3H)(H2O)2]⋅H2O 2, and [Pt((O,O)Hp−2H)Cl(H2O)3] 3, were studied by UV-Vis, IR, EPR and XPS spectra, thermal (TGS, DSC), potentiometric and magnetic methods. The newly synthesized complexes show promising cytotoxic activity comparable with that of cis-platin in in vitro tests against a panel of human leukemia cell lines. The observed cytotoxicity of the complex 2 against SKW-3 cells (KE-37 derivative) is due to induction of cell death through apoptosis.

A program for simulation of powder-type EPR spectra

An algorithm of a computer program for simulation of powder type EPR spectra (S=1/2,I≠0) is described. For determination of the energy levels, the perturbation approach is used and corrections up to second order due to hyperfine, quadrupole, and nuclear Zeeman coupling are taken into account. No restrictions on the mutual orientations of the eigenvectors ofg, hyperfine, and quadrupole tensors are imposed. Simulated spectra for a model paramagnetic system (S=1/2,I=3/2) with axial symmetry and noncoinciding directions ofg‖ andA‖ are presented.

COPPER(II) COMPLEXES OF A NEW CYNNAMYL DERIVATIVE OF THE ANTIBIOTIC RIFAMPICIN

Abstract The complexation of copper(II) with a new semisynthetic cynnamyl derivative of the antibiotic rifampicin was investigated in methanol solutions using UV-VIS and EPR spectroscopy. The process was studied at different ligand-to-metal ratios (L:M from 100:1 to 1:10). In a ligand excess, two mononuclear complexes of the type CuL are formed with different modes of coordination. At equimolar concentrations of the reagents, another polynuclear complex with empirical formula Cu(L)ClO 4 is obtained and isolated in a solid phase. Each Cu 2+ in it is bound with two O-donors (0–1 and 0–8) from one ligand molecule and by O-4 and N-donors (CHNH) from another one.