G. Gencheva

Monomeric Pt(II) and Pd(II) complexes with Creatinine. Crystal structure of tetrakis-(Creatinine) platinum(II) diperchlorate

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)°.

Structure of Ni(II)-creatinine complex species formed in non-aqueous media

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.

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.

Complex formation of monomeric and dimeric copper(II) complexes with creatinine in organic media

Abstract New monomeric and dimeric copper(II) complexes with creatinine were synthesized in organic media. Formation of different complex species depending on the reaction medium was proved. Using spectroscopic (EPR and IR) and magnetochemical methods, the structure of the complexes obtained was studied.

In vitro pharmacological study of monomeric platinum(III) hematoporphyrin IX complexes

SummaryThree stable mononuclear hematoporphyrin IX ((7,12-bis(1-hydroxyethyl)-3,8,13,17-tetramethyl-21H-23H-porphyn-2,18-dipropionic acid), Hp) complexes of PtIII, namely cis-[ PtIII(NH3)2(Hp−3H)(H2O)2].H2O 1, [PtIII(Hp−3H)(H2O)2].H2O 2 and [PtIII((O,O)Hp−2H)Cl(H2O)3] 3 with distorted octahedral structure and (dz2)1 ground state have been tested in vitro for antineoplastic activity in a panel of tumor cell lines. The novel platinum(III) complexes showed cytotoxic activity in a concentration-dependent manner with IC50 values comparable to those of referent cytotoxic agent cisplatin together with lower cytotoxicity against renal cells. Further detailed evaluation of the active analogue 2 and the less active complex 3 showed that their potency greatly correlates with the ability to induce apoptosis and to bind DNA. Despite the structural dissimilarities between complex 2 and cisplatin, their DNA-adducts were equally effectively recognized and repaired by the nucleotide excision repair system. Complex 2 showed quite superior ability to accumulate in K-562 cells relative to cisplatin.

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

Platinum(Iii) Formation and Stabilization as "Platinum Blues" With Different Types of Ligands in the Course of Their Interaction With PtCl42- and cis-Pt(Nh3)2Cl2

Studying the kinetics of PtCl42-cis-[Pt(NH3)2(H2O)2]2+ and cis-Pt(NH3)2Cl2 (cis-DDP) reactions with different types of ligands using spectrophotometric, Potentiometric and EPR methods, the conditions for Pt(III) formation as transient species and its further stabilization as “Platinum Blue” complexes were found. A general method for obtaining “Platinum Blue” species is suggested.

In vitro evaluation of a stable monomeric gold(II) complex with hematoporphyrin IX: cytotoxicity against tumor and kidney cells, cellular accumulation, and induction of apoptosis.

The antineoplastic potential of a stable monomeric Au(II) complex with hematoporphyrin IX (Hp), namely [Au(II)Hp−2H.(H2O)2], was investigated in a panel of tumor cell lines. The complex exhibits strong cytotoxicity, whereby the leukaemia- and lymphoma-derived cell lines are more sensitive, with IC50 values comparable to those of the reference anticancer drug cisplatin. In contrast, the solid tumor models are more sensitive to the platinum drug. A comparative assessment of both agents against the human kidney cell line 293T has shown that [Au(II)Hp−2H.(H2O)2] is less cytotoxic. The gold complex induces oligonucleosomal DNA fragmentation in tumour cells following 24-hour treatment and hence its cytotoxic effect is at least partly mediated by induction of apoptotic cell death. A prominent intracellular gold accumulation was detected after treating tumor cells with [Au(II)Hp−2H.(H2O)2] which shows that its putative pharmacological targets are readily accessible after a short incubation period.

Monomeric Au(II) complex with hematoporphyrin IX

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.

Dimeric and oligomeric platinum(II, II), (II, III) and palladium(II, II) complexes with creatinine

Abstract Paramagnetic tetrameric “Platinum Blue” species and dimeric complexes of platinum(II) and palladium(II) with creatinine were synthesized and their structure and coordination mode of the ligand studied by means of EPR, IR, TG and DTA methods. The results show that by varying the reaction conditions (acidity, metal-to-ligand ratio, presence of oxygen), different platinum and palladium complexes are obtained.