Catherine P. Raptopoulou

Anti-inflammatory drugs interacting with Zn(II), Cd(II) and Pt(II) metal ions

Complexes of Zn(II), Cd(II) and Pt(II) metal ions with the anti-inflammatory drugs, 1-methyl-5-(p-toluoyl)-1H-pyrrole-2-acetic acid (Tolmetin), alpha-methyl-4-(2-methylpropyl)benzeneacetic acid (Ibuprofen), 6-methoxy-alpha-methylnaphthalene-2-acetic acid (Naproxen) and 1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid (indomethacin) have been synthesized and characterized. In the structurally characterized Cd(naproxen)2 complex the anti-inflammatory drugs acts as bidentate chelate ligand coordinatively bound to metal ions through the deprotonated carboxylate group. Crystal data for 1: [C32H26O8Cd], orthorhombic, space group P22(1)2(1), a = 5.693(2) (A), b = 8.760(3) (A), c = 30.74(1) (A), V = 1533(1) A3, Z = 2. Antibacterial and growth inhibitory activity is higher than that of the parent ligands or the platinum(II) diamine compounds.

Copper(II) complexes with phenoxyalkanoic acids and nitrogen donor heterocyclic ligands: structure and bioactivity

The copper complexes with the phenoxyalkanoic acids MCPA, 2,4-D, 2,4,5-T and 2,4-DP in the presence of a nitrogen donor heterocyclic ligand, phen or bipyam, were prepared and characterized. Interaction of Cu(II) with phenoxyalkanoic acids and bipyam leads to dinuclear or uninuclear neutral complexes while in the presence of phen uninuclear neutral or cationic forms have been isolated. The crystal structure of bis(1,10-phenanthroline)(2-methyl-4-chloro-phenoxyacetato)copper(ll) chloride-methanol(1/1)-water(1/0.6), 1 has been determined and refined by least-squares methods using three-dimensional MoK, data. 1 crystallizes in space group P1, in a cell of dimensions a = 14.577(6)A, b = 1 1.665(5) A, c = 12.249(6) A, alpha = 98.38( 1)degrees, beta = 112.18( 1) degrees, gamma = 104.56(1 ) degrees, V= 1,798( 1) A3 and Z= 2. The cyclic voltammograms of uninuclear cationic complexes in dmf exhibit an extra cathodic wave due to the chloride ion. The available evidence supports an increasing antimicrobial effeciency for the cationic complexes.

Thegem-Diol Form of (py)2CO as a Ligand in Cobalt(II) Carboxylate Clusters: A Cubane Complex and a Novel Nonanuclear Species with a Vertex-Sharing Double Square Pyramidal Structure

A vertex-sharing double square pyramid of cobalt(II) ions (see picture) is present in the nonanuclear complex 1, obtained by treating cobalt acetate with 0.5 equivalents of (py2 )CO. The corresponding 1:1 reaction gave 2, which has a central core with a cubane structure. py=pyridine.

Coordinating properties of 2-acetylpyridine thiosemicarbazone. Palladium(II) complexes with neutral and deprotonated ligand. X-ray structure of bromo(2-acetylpyridine thiosemicarbazonato) palladium(II)

Abstract The preparation of the complexes PdLX, [Pd(HL) 2 ]X 2 and PdL 2 (X = Cl, Br; HL and L the neutral and deprotonated ligand) is described. The new complexes have been characterized by elemental analyses, conductivity measurements and spectroscopic (IR and UV-vis) studies and the crystal and molecular structure of PdLBr has been determined by single-crystal X-ray diffraction. The palladium atom has a square planar geometry with three donor atoms (NNS) coming from L to form a planar tricyclic ligating system, and one bromide atom. All data are discussed in terms of assigned structural type and the nature of the bonding. The protonation constants of the ligand, K a1 and K a2 , were determined by spectrophotometry and the logarithms of their values were found to be equal to 11.43 ± 0.02 and 3.98 ± 0.02.

CuII-herbicide complexes: structure and bioactivity

Abstract Copper complexes with the commercial auxin herbicides 2,4-dichlorophenoxy-acetic acid (2,4-D), 3,4-dichlorophenoxy-acetic acid (3,4-D), 2,4,5-trichlorophenoxy-acetic acid (2,4,5-T), 2-methyl-4-chloro-phenoxy-acetic acid (MCPA), 2,3-dichlorophenoxy-acetic acid (2,3-D) and 2-(2,4-dichlorophenoxy)-propanoic acid (2,4-DP) in the presence or not of 2,2′-bipyridine (bipy), an antimicrobial agent, were prepared and characterized. The available evidence supports a dimeric structure for the 2,3-D complex, while the presence of bipy leads to monomeric forms. The solution behaviour of dinuclear complexes in dimethylformamide (DMF) has shown that the complexes are converted to monomeric compounds by the addition of more than 1:2 of bipy. The cyclic voltammograms of dimers in DMF suggest that the complexes retain the dimeric structure in solution. The electron spin resonance spectra of the compound (aqua)(2,2′-bipyridine)bis(2-methyl-4-chloro-phenoxyacetato) copper(II) (I) show features characteristic of the presence of an S = 1 triplet state. The crystal structure of 1 was determined and refined by least-squares methods using three-dimensional Mo Kα data. 1 crystallizes in the space group C2 c , in a cell of dimensions a=40.49(1), b=7.286(3), c=19.617(6) A , β=103.23(1)°, V=5634(3) A 3 , Z=8 . Study of the antimicrobial activity showed that the presence of bipy increases the efficiency 4–8 times.

Synthesis and characterization of tetrakis-μ-2-[(2,6dichlorophenyl) amino] benzeneacetodiaquodicopper(II) dihydrate and tetrakis-μ-2-[(2,6dichlorophenyl)amino]benzeneaceto dimethylformamidodicopper(II)

Abstract Complexes of diclofenac (L), [CuL2(H2O)]22H2O, and [CuL2(DMF)]2 were prepared by the reaction of the sodium salt of this potent antiinflammatory drug with CuCl2. The new symmetric binuclear copper(II) complex [CuL2(DMF)]2 crystallizes in the monoclinic space group P21/n with cell constants a = 10.807(1), b = 15.429(2), c = 19.360(2), β = 92.508(3), V = 3225(1) A 3 , and Z = 2 . The structure was determined from 5456 out of a total of 5768 unique reflections. The final values for R1, wR2, and GOF for all data are 0.0602, 0.1066, and 1.030, respectively. The crystal structure consists of a binuclear quadruply bridged neutral molecule. The four carboxylato groups from four ligands are in the familar bidentate syn,syn η1:η1:μ2 bridging mode. The metal coordination geometry is described as a perfect square bipyramid with a water or dimethyloformamide oxygen occupying both apical positions. Optical, infrared, electron paramagnetic resonance, magnetic, and electrochemical properties of these complexes are also reported.

Unusual structural types in nickel cluster chemistry from the use of pyridyl oximes: Ni5, Ni12Na2, and Ni14 clusters.

Syntheses, crystal structures, and magnetochemical characterization are reported for the three new nickel(II) clusters [Ni(14)(OH)(4)(N(3))(8)(pao)(14)(paoH)(2)(H(2)O)(2)](ClO(4))(2) (1), [Ni(12)Na(2)(OH)(4)(N(3))(8)(pao)(12)(H(2)O)(10)](OH)(2) (2), and [Ni(5)(ppko)(5)(H(2)O)(7)](NO(3))(5) (3) (paoH = pyridine-2-carbaldehyde oxime, ppkoH = di-2-pyridyl ketone oxime). The reaction of Ni(ClO(4))(2).6H(2)O with paoH and NBu(n)(4)N(3) in H(2)O/MeCN in the presence of NEt(3), gave 1 in 65% yield. Complex 2 was obtained in 60% yield from the reaction of NiCl(2).6H(2)O with paoH and NaN(3) in H(2)O/MeCN in the presence of NaOH. The reaction of Ni(NO(3))(2).6H(2)O with ppkoH in EtOH in the presence of LiOH afforded complex 3 in 75% yield. The complexes all contain novel core topologies. The core of 1 comprises a central Ni(4) rhombus between two Ni(5). Complex 1 is the largest metal/oxime cluster discovered to date, as well as the first Ni(II)(14) coordination complex and the largest Ni(II)/N(3)(-) cluster. Complex 2 has a Ni(12)Na(2) topology that is very similar to that of 1, but with two central Ni(II) atoms of 1 replaced with Na(I) atoms. The core of 3 consists of four Ni(II) atoms forming a highly distorted tetrahedron, with the fifth Ni(II) atom lying almost on one of the edges. Variable-temperature, solid-state dc susceptibility and magnetization studies were carried out on complexes 1-3, and these were complemented with ac susceptibility data for 1 and 2. Fitting of the obtained M/(Nmu(B)) vs H/T data by matrix diagonalization and including axial zero-field splitting (D) gave ground-state spin (S) and D values of S = 6, D = -0.12(3) cm(-1) for 1 and S = 3, D = -0.20(5) cm(-1) for each of the two essentially noninteracting S = 3 Ni(6) subunits of 2. The data for 3 indicate antiferromagnetic exchange interactions and an S = 1 ground state. A simple 2-J model was found to be adequate to describe the variable-temperature dc susceptibility data. The combined work demonstrates the ligating flexibility of pao(-) and ppko(-), and their usefulness in the synthesis of polynuclear Ni(x) clusters with or without the presence of ancillary ligands.

A new family of nonanuclear lanthanide clusters displaying magnetic and optical properties.

The initial employment of 2-(hydroxymethyl)pyridine in 4f metal chemistry has afforded a new family of Ln(III)(9) clusters with a sandglass-like topology and dual physical properties; the Dy(III) member shows single-molecule magnetism behavior, while the Eu(III) analogue exhibits intense red photoluminescence.

Synthesis, spectroscopic, and structural characterization of the first aqueous cobalt(II)-citrate complex: toward a potentially bioavailable form of cobalt in biologically relevant fluids.

Abstract Citric acid represents a class of carboxylic acids present in biological fluids and playing key roles in biochemical processes in bacteria and humans. Its ability to promote diverse coordination chemistries in aqueous media, in the presence of metal ions known to act as trace elements in human metabolism, earmarks its involvement in a number of physiological functions. Cobalt is known to be a central element of metabolically important biomolecules, such as B12, and therefore its biospeciation in biological fluids constitutes a theme worthy of chemical and biological perusal. In an effort to unravel the aqueous chemistry of cobalt in the presence of a physiologically relevant ligand, citrate, the first aqueous, soluble, mononuclear complex has been synthesized and isolated from reaction mixtures containing Co(II) and citrate in a 1 :2 molar ratio at pH∼8. The crystalline compound (NH4)4[Co(C6H5O7)2] (1) has been characterized spectroscopically (UV/vis, EPR) and crystallographically. Its X-ray structure consists of a distorted octahedral anion with two citrate ligands fulfilling the coordination requirements of the Co(II) ion. The magnetic susceptibility measurements of 1 in the range from 6 to 295 K are consistent with a high-spin complex containing Co(II) with a ground state S=3/2. Corroborating this result is the EPR spectrum of 1, which shows a signal consistent with the presence of a Co(II) system. The spectroscopic and structural properties of the complex signify its potential biological relevance and participation in speciation patterns arising under conditions consistent with those employed for its synthesis and isolation.

Lead–citrate chemistry. Synthesis, spectroscopic and structural studies of a novel lead(II)–citrate aqueous complex

Abstract The interaction of lead with biologically relevant ligands, such as citrate, constitutes a major research thrust relating to toxic effects exerted on humans. Reaction of Pb(NO3)2 with citric acid in water at pH 2 and various ratios (1:1–1:3) yielded the first Pb–citrate species, which was characterized analytically and spectroscopically (FT-IR). X-ray crystallographic studies were carried out and showed the novel compound to be [Pb(C6H6O7)]n·nH2O. The geometry around Pb2+ appears to be distorted trigonal bipyramidal with PbO distances ranging from 2.397(7) to 2.527(6) A and the lone pair on Pb2+ occupying one of the three basal plane positions. Citrate binds Pb2+ forming rhomboidal Pb2O2 units, while it subtends its terminal carboxylate onto a proximal Pb2+, thus linking adjacent Pb2O2 units into a chain along the a axis. The involvement of citrate in hydrogen bonds with water molecules and abutting Pb–citrate moieties leads to a stable structure. The stability of the species formed and eventually isolated from aqueous solutions as well as its reactivity toward bases present useful information on the chemistry in biological media and its relevance to the known biotoxicity of lead.