Barbara Barszcz

Crystal and molecular structures of eight-coordinate (CuN4O4) and six-coordinate (CuN4O2) Cu(II) complexes with 4-methyl-5-imidazole-carboxaldehyde or 1-benzyl-2-hydroxymethylimidazole, respectively: Spectroscopic and potentiometric studies

Abstract The synthesis and characterisation of two novel Cu(II) eight and six coordinate compounds with the bidentate ligands 4-methyl-5-imidazolecarboxaldehyde (4-Me-5-CHOIm) and 1-benzyl-2-hydroxymethylimidazole (1-Bz-2-CH2OHIm) are described. Single crystals of [Cu(4-Me-5-CHOIm)4](H2O)2(NO3)2 (1) and [Cu(1-Bz-2-CH2OHIm)4](NO3)2 (2) were used in structure determinations. The two compounds both crystallise in the monoclinic space group P1 with Z=2 for (1) and Z=1 for (2). The structural data for (1) indicated that Cu(II) ion is involved in a flattened tetrahedron of N(1), N(2), N(3) and N(4) atoms of imidazoles ring as well as in a more distant elongated tetrahedron of four of the z-axis oxygen atoms O(1), O(2), O(3), O(4) of aldehyde groups. The coordination scheme of the six-coordinate Cu(II) complex (2) is a slightly distorted tetragonal bipyramid and the ligands act as a monodentate and bidentate. Additionally, the coordination processes with Cu(II) were detected and characterised in solution using spectroscopic (EPR and UV–VIS) as wall as potentiometric methods.

Comparison of 1-hydroxymethyl-3,5-dimethylpyrazole and 1-benzyl-2-hydroxymethylimidazole coordination properties towards copper(II)

Abstract Using 1-hydroxymethyl-3,5-dimethylpyrazole as the starting ligand and 2-propanol as the solvent and a molar ratio Cu:L, 1:4, a dinuclear Cu(II) complex has been obtained. The microanalytical data and the crystal structure reveal that the dicopper complex with two bridging methoxide groups contains the 3,5DMePz, 1-CH2O-3,5DMePz and BF4− ligands which are received during the coordination process. The compound shows an antiferromagnetic intramolecular interaction between the Cu(II) ions.

Assembling novel Cd(II) complexes with multidentate nitrogen donor ligands obtained in situ from the system: zerovalent copper, cadmium oxide, 1-hydroxymethyl-3,5-dimethylpyrazole and ammonium thiocyanate.

A novel 3D coordination polymer [Cd2(L(1))(2)(SCN)(4)(MeOH)(2)](n) (1) and monomeric [Cd(NCS)(2)L(2)] (2) (L(1) = urotropine, L(2) = tris(1-(3,5-dimethylpyrazolylmethyl))amine) have been prepared in a one-pot synthesis using 1-hydroxymethyl-3,5-dimethylpyrazole as the starting ligand. The most prominent feature is the formation in situ of the organic compounds: urotropine and scorpionate-tripodal ligands.

Synthesis, X-ray structure and spectroscopic investigation of an eight-coordinate cadmium(II) complex

Reaction of 4-methylimidazole-5-carbaldehyde (L) with cadmium(II) nitrate (M : L = 1 : 2; EtOH) yields a novel eight-coordinate mononuclear complex, [CdL2(NO3)2]. X-ray structural analysis indicates that the Cd(II) ion possesses what can be described as a double coordination sphere. The inner coordination sphere is pseudo-tetrahedral and consists of four atoms, N(1), N(11), O(21) and O(42), with bond lengths ranging from 2.252(2) to 2.371(2) Å. The second or outer coordination sphere is composed of four oxygen donors, O(7), O(17), O(22) and O(41), with Cd–O distances of 2.543(2) to 2.756(2) Å. The atoms of the external coordination sphere form pyramids with the pseudo-tetrahedral faces of the inner coordination sphere. IR and Raman spectra confirm the stabilization of the Nπ–H isomer of the ligand.

A novel single-site manganese(II) complex of a pyridine derivative as a catalase mimetic for disproportionation of H2O2 in water.

A novel single site Mn(II) complex was successfully synthesized and tested in the aqueous disproportionation of hydrogen peroxide. The complex was found to be stable (HR-XAS) and exhibits catalase-like activity in neutral pH. Theoretical calculations suggested a reaction mechanism involving two complexes, changes in metal oxidation state and proton shuttling.

Eight- and six-coordinated Mn(II) complexes of heteroaromatic alcohol and aldehyde: crystal structure, spectral, magnetic, thermal and antibacterial activity studies.

Crystal, molecular and electronic structure of new manganese(II) compounds: [Mn(2-CH2OHpy)2(NO3)2] (1), [Mn(4-CHO-5-MeIm)2(NO3)2] (2) and [Mn(4-CHO-5-MeIm)2Cl2] (3), where 2-hydroxymethylpyridine (2-CH2OHpy) and 5(4)-carbaldehyde-4(5)-methylimidazole (5(4)-CHO-4(5)-MeIm), have been characterised using X-ray, spectroscopic, magnetic and TG/DTG data. In compounds 1 and 2, the Mn(II) ion is eight-coordinated forming distorted pseudo-dodecahedron, that is rather unusual for the manganese(II) complexes, whereas in 3 the Mn(II) ion environment is a distorted octahedron. The high coordination number (CN=8) of 1 and 2 results from bidentate character of the nitrate ligands. The X-band EPR spectra of compounds 2 and 3 exhibit fine structure signals resulting from zero-field splitting (ZFS) of the spin states for high spin d(5) Mn(II), whereas for 1 the broad isotropic signals were observed. The estimation of ZFS for individual Mn(II) ions was carried out for all compounds using DFT calculations. The free ligands and their manganese(II) complexes have been tested in vitro against gram-positive and gram-negative bacteria in order to assess their antimicrobial properties.

Synthesis and physicochemical characterization of two lead(II) complexes with O-, N-donor ligands. Lone pair functionality and crystal structure.

A dinuclear [Pb2(4-CHO-5-MeIm)6(NO3)2](NO3)2 (1) and a polynuclear [Pb(2-pzc)2(H2O)]n (2) complexes (where 5(4)-carbaldehyde-4(5)-methylimidazole (5(4)-CHO-4(5)-MeIm) and pyrazine-2-carboxylic acid (2-pzcH)) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray crystallography. Structural determination for complex 1 reveals a cationic species [Pb(4-CHO-5-MeIm)3]2+ connected through bridging nitrate(V) ions. There are also an uncoordinated nitrate ions as counterions. Complex 2 is a three-dimensional architecture consisting of Pb6O12 building units. The pyrazine-2-carboxylato ligand behaves as a chelating agent and a bi-connective bridge. The coordination polyhedra around lead(II) ion could be described as a distorted docecahedron (1) or monocapped trigonal prism (2). The luminescent properties of 1 and 2 investigated in the solid state at room temperature indicate structure-dependent photoluminescent properties. The DFT calculations and the X-ray structural data point on rather hemidirected type of coordination around Pb(II) ions of 1 and 2.

An efficient process to directly convert 1-hydroxymethyl-3,5-dimethylpyrazole to Cd(II) complexes via C–N bond creation: cytotoxicity and factors controlling the structures

We have demonstrated a simple process that involves one-pot, one-step reactions leading to efficient preparation of new cadmium complexes with N4-donating ligands [CdX2L1] (X = I− (1), Br− (2) L1 = tris(1-(3,5-dimethylpyrazolyl)methyl)amine). The most prominent feature of the synthesis is the in situ formation of a new organic tripodal ligand (L1) in a condensation reaction between a starting ligand (1-hydroxymethyl-3,5-dimethylpyrazole) and ammonia. A single-crystal X-ray analysis confirmed that the complexes obtained are monomers (1, 2) with octahedral geometry of the cadmium centres. Complex 3 has a cationic–anionic structure [Cu(LOH)2CH3OH][CdCl4] and has been synthesised by the reaction of CdO and NH4Cl in the presence of zerovalent copper (powder). IR, EPR, 1H and 13C NMR, as well as simultaneous TG/DTG were carried out to characterise the products. Moreover, we try to compare the cytotoxic profile of CdO and cadmium salts with Cd(II) complexes. Besides [CdX2L1] (1, 2) we take into consideration [Cd2(L2)2(SCN)4(MeOH)2]n (4) and [Cd(SCN)2L1] (5) complexes. Biological studies demonstrated that Cd(II) complexes with the N-scorpionate ligand (1, 2 and 5) have similar cytotoxicity, which points to a structure–cytotoxicity relationship. Thus, all the complexes (except 4) exhibited a lower cytotoxic activity compared to a cadmium ion in salts.

Synthesis, crystal structures and spectroscopic studies on trans and cis isomers of Co(II) complexes with 1-benzyl-2-hydroxymethylimidazole

Abstract By carrying out the synthesis in a special way, two novel cobalt(II) isomers of trans(O)-[Co(1-Bz-2-CH2OHIm)4](NO3)2 (1) and cis(O)-[Co(1-Bz-2-CH2OIm)4](NO3)2·1.5H2O (2) have been separated. The crystal structures of the Co(II) isomers show the triclinic space group P1 (1) and the monoclinic space group C2/c (2). The coordination geometry around the Co atom is approximately octahedral (1) or very distorted octahedral (2) and the Co(II) ions are surrounded by four nitrogen atoms of the four imidazole rings and two oxygen atoms of the hydroxymethyl group. Two of the ligands act as a monodentate and two as a bidentate, forming the five–membered chelate ring with the central ion. The structural data obtained for the Co(II) isomers were confirmed by IR and UV–Vis spectroscopic methods.

Recent Research Trends on Bismuth Compounds in Cancer Chemo- and Radiotherapy

BACKGROUND Application of coordination chemistry in nanotechnology is a rapidly developing research field in medicine. Bismuth complexes have been widely used in biomedicine with satisfactory therapeutic effects, mostly in Helicobacter pylori eradication, but also as potential antimicrobial and anti-leishmanial agents. Additionally, in recent years, application of bismuth-based compounds as potent anticancer drugs has been studied extensively. METHODS Search for data connected with recent trends on bismuth compounds in cancer chemo- and radiotherapy was carried out using web-based literature searching tools such as ScienceDirect, Springer, Royal Society of Chemistry, American Chemical Society and Wiley. Pertinent literature is covered up to 2016. RESULTS In this review, based on 213 papers, we highlighted a number of current problems connected with: (i) characterization of bismuth complexes with selected thiosemicarbazone, hydrazone, and dithiocarbamate classes of ligands as potential chemotherapeutics. Literature results derived from 50 papers show that almost all bismuth compounds inhibit growth and proliferation of breast, colon, ovarian, lung, and other tumours; (ii) pioneering research on application of bismuth-based nanoparticles and nanodots for radiosensitization. Results show great promise for improvement in therapeutic efficacy of ionizing radiation in advanced radiotherapy (described in 36 papers); and (iii) research challenges in using bismuth radionuclides in targeted radioimmunotherapy, connected with choice of adequate radionuclide, targeting vector, proper bifunctional ligand and problems with 213Bi recoil daughters toxicity (derived from 92 papers). CONCLUSION This review presents recent research trends on bismuth compounds in cancer chemo- and radiotherapy, suggesting directions for future research.