Interactions between metal ions and carbohydrates. Syntheses and spectroscopic studies of several lanthanide nitrate–d-galactitol complexes

Two complexes of neutral d-galactitol (C₆H₁₄O₆, G) with terbium nitrate, TbGN(I) and TbGN(II), and one complex with samarium nitrate SmGN were synthesized and characterized. From IR, FIR, THz and luminescence spectra the possible coordinations were suggested, and the single-crystal X-ray diffraction results confirm the spectroscopic conclusions. In TbGN(I) (Tb(NO₃)₃·C₆H₁₄O₆·3H₂O), the Tb³⁺ is 9-coordinated with three water molecules and six OH groups from two d-galactitol molecules. Nitrate ions do not coordinate to metal ions, which is different from other reported lanthanide nitrate–d-galactitol complexes. In TbGN(II) and SmGN (Ln(NO₃)₃·C₆H₁₄O₆), Ln³⁺ is 10-coordinated with six OH groups from two d-galactitol molecules and four oxygen from two bidentate nitrate ions, and one nitrate ion is hydrogen bonded. No water exists in the structures. d-Galactitol molecules provide their 1-, 2- and 3-hydroxyl groups to coordinate with one metal ion and their 4-, 5- and 6-hydroxyl groups to coordinate with another metal ion in the three structures. There is still a new topological structure that can be observed for lanthanide–d-galactitol complexes, which indicates that the coordinations between hydroxyl groups and metal ions are complicated.     

Interactions between metal ions and carbohydrates: the coordination behavior of neutral erythritol to zinc and europium nitrate

The single crystals of coordinated complexes of neutral erythritol (C4H10O4) with zinc nitrate and europium nitrate were synthesized and studied using FT-IR and single crystal X-ray diffraction analysis. In the structure of Zn(NO3)2.C4H10O4, ZnEN (E denotes erythritol, N represents nitrate), Zn2+ is coordinated to four hydroxyl groups from two erythritol molecules and two oxygen atoms from two nitrates. Two Zn2+ are connected by one erythritol molecule to form Zn(C4H10O4)(NO3)2 chain, and layers formed by above chain pile to produce 3D structures. In the structure of Eu(NO3)3.C4H10O4.C2H5OH, EuEN, Eu3+ is 10-coordinated by six oxygen atoms from three nitrate ions, three hydroxyl groups from one erythritol molecule and one hydroxyl group from ethanol. In the above erythritol complexes, two hydroxyl groups of erythritol coordinate to one metal ion and the other two to another metal ion or erythritol acts as three-hydroxyl groups donor. The OH groups of erythritol act as ligand to coordinate to metal ions on one hand, one the other hand, OH groups form hydrogen bonds network to build three-dimensional structures.     

Interactions between metal ions and carbohydrates. The coordination behavior of neutral erythritol to neodymium ion

A single crystal of a coordinated complex of neutral erythritol (C4H10O4,E) with a neodymium ion, NdE(II), was synthesized and studied using FT-IR and X-ray diffraction analysis. In NdE(II) (NdCl3.2.5C4H10O4.C2H5OH) the Nd3+ coordinates with one chloride ion and eight OH groups from three erythritol molecules. There are two neodymium centers linked by one erythritol molecule with same coordination structure in the molecule. Two erythritol molecules provide 1,3,4-hydroxyl groups to coordinate with a neodymium ion; another erythritol molecule coordinates to two Nd ions via its 1,2-hydroxyl groups and 3,4-hydroxyl groups, respectively. The OH groups of erythritol act as ligand to coordinate to neodymium ions, and OH groups of erythritol form hydrogen bond networks that link chain and layer together to build three-dimensional structures. The ratio of metal to ligand is 1:2.5. The structure of NdE(II) is more complicated than the previously reported NdE(I), which is NdCl3.C4H10O4.6H2O; in NdE(I), Nd3+ is coordinated to four hydroxyl groups from two erythritol molecules, four water molecules and one chloride ion. The results indicate the complexity of metal-sugar interaction.     

Complexes of lanthanoid salts with macrocyclic ligands. Part 32. Synthesis and characterization of the complexes between lanthanoid nitrates and a tetraoxadiaza macrocycle

Lanthanoid nitrates react with 1,7,10,16-tetraoxa- 4,13-diaza-N,N′-dimethylcyclooctadecane, Me₂(2,2), to give complexes with two different metal:ligand ratios, 1:1 (Ln = La, Ce, Tb) and 4:3 (Ln = Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho). The complexes were isolated from anhydrous solutions in acetonitrile and characterized by elemental analysis, X-ray diffraction, magnetic susceptibility measurements and vibrational analysis.The La and Ce 1:1 complexes are non-ionic and probably 12-coordinated, with the metal ion bound to the six donor atoms of the ligand and to three bidentate nitrate ions. The 4:3 complexes are ionic; they contain three bis(nitrato) complex cations [Ln(NO₃)₂·Me₂(2,2)]⁺ and one hexakis(nitrato) anion [Ln(NO₃)₆]³⁻. Spectroscopic data, including luminescence spectra, point to the 1:1 Tb-complex as being a 4:3 complex with an additional outer-sphere coordinated molecule of ligand.In solution, the 1:1 complexes remain essentially non-ionic, although some dissociation cannot be ruled out, whereas the 4:3 complexes behave as 2:1 (of even 3:1) electrolytes.     

Interactions between metal ions and carbohydrates. The coordination behavior of neutral erythritol to lanthanum and erbium ions

Lanthanide ions and erythritol form metal–alditol complexes with various structures. Lanthanum nitrate and erbium chloride coordinate to erythritol to give new coordination structures. The lanthanum nitrate–erythritol complex (LaEN), 2La(NO₃)₃·C₄H₁₀O₄·8H₂O, La³⁺ exhibits the coordination number of 11 (namely 11 polar atoms bound to one lanthanum) and is 11-coordinated to two hydroxyl groups from one erythritol molecule, six oxygen atoms from three nitrate ions and three water molecules. One erythritol molecule is coordinated to two La³⁺ ions and links the two metal ions together. The ratio of M:L is 2:1. The erbium chloride–erythritol complex (ErE), ErCl₂·C₄H₉O₄·2C₂H₅OH was obtained from ErCl₃ and erythritol in aqueous ethanol solution and the structure shows that deprotonation reaction occurs in the reaction process. The Er³⁺ cation is 8-coordinated with three hydroxyl groups of one erythritol molecule, two hydroxyl groups from another erythritol molecule, two ethanol molecules, and one chloride ion. Erythritol provides its three hydroxyl groups to one erbium cation and two hydroxyl groups to another erbium cation, that is, one hydroxyl group is coordinated to two metal ions and therefore loses its hydrogen atom and becomes a oxygen bridge. Another chloride ion is hydrogen bonded in the structure. The results indicate the complexity of metal–sugar coordination.     

Crystal structures and spectroscopic characterization of galactitol complexes of trivalent lanthanide and divalent alkaline earth chlorides

Crystal structures and FT-IR spectra of metal ion-galactitol (C6H14O6, the ligand here abbreviated as L) complexes: 2LaCl3*C6H14O6*10H2O and SrCl2*C6H14O6 complexes are reported. Crystal data of lanthanide chlorides (La3+, Nd3+, Sm3+, Eu3+, Tb3+)-galactitol complexes and alkaline earth chlorides (Ca2+, Sr2+)-galactitol complexes published earlier are summarized. Unlike other lanthanide ion-galactitol complexes (2MCl3*C6H14O6*14H2O), lanthanum ions give rise to two different structures: LaCl3*C6H14O6*6H2O (LaL1) and 2LaCl3*C6H14O6*10H2O (LaL2). Sr2+-galactitol complexes also crystallized with two structures: SrCl2*C6H14O6*4H2O (SrL1) and SrCl2*C6H14O6 (SrL2). These metal ions thus give different coordination structures with galactitol. The crystal structures and FT-IR spectra of lanthanide ion and alkaline earth ion-galactitol complexes were integrated to interpret the coordination modes of different metal ions. Similar IR spectra demonstrate the same coordination modes of the complexes.     

Syntheses, crystal structures, and bond valence sum analyses of lanthanide complexes with a planar pentadentate ligand

The syntheses and X-ray crystal structures of the Eu, Gd, Dy, Ho, and Er nitrate complexes of the pentadentate ligand 2,6-diacetylpyridine bis acetic acid hydrazone, or H₂dapaah, are reported. The complexes can be divided into 3 groups depending on the number of water molecules per metal ion. The Ln · 4H₂O complexes with Eu, Gd and Dy are isomorphous, with the Ln ion being 10 coordinate. The Ln · 6H₂O group includes Ho and Er, where the cation is 9 coordinate. The final complex Gd · 5H₂O is 10 coordinate like the Eu, Gd and Dy complexes, but the additional water molecule has stabilized an ordered crystal. The bond valence sum method has been used to analyze the bonding in the complexes and has suggested that bond valence equalization in three dimensions may be an important concept.     

Sugar interaction with metal ions. The coordination behavior of neutral galactitol to Ca(II) and lanthanide ions

The crystal structures of CaCl(2).galactitol.4 H(2)O and 2EuCl(3).galactitol.14 H(2)O were determined to compare the coordination behavior of Ca and lanthanide ions. The crystal system of the Ca-galactitol complex, CaCl(2).C(6)H(14)O(6).4 H(2)O, is monoclinic, Cc space group. Each Ca ion is coordinated to eight oxygen atoms, four from two galactitol molecules and four from water molecules. Galactitol provides O-2, -3 to coordinate to one Ca(2+), and O-4, -5 with another Ca(2+), to form a chain structure. The crystal system of the Eu-galactitol complex, 2EuCl(3).C(6)H(14)O(6).14 H(2)O, is triclinic, P1; space group. Each Eu ion is coordinated to nine oxygen atoms, three from an alditol molecule and six from water molecules. Each galactitol provides O-1, -2, -3 to coordinate with one Eu(3+) and O-4, -5, -6 with another Eu(3+). The other water molecules are hydrogen-bonded in the structure. The similar IR spectra of Pr-, Nd-, Sm-, Eu-, Dy-, and Er-galactitol complexes show that those lanthanide ions have the same coordination mode to neutral galactitol. The Raman spectra also confirm the formation of metal ion-carbohydrate complexes.     

Uracilato and 5-halouracilato complexes of Cu(II), Zn(II) and Ni(II). X-ray structures of [Cu(uracilato-N(1))(2)(NH(3))(2)].2(H(2)O), [Cu(5-chlorouracilato-N(1))(2)(NH(3))(2)](H(2)O)(2), [Ni(5-chlorouracilato-N(1))(2)(en)(2)].2H(2)O and [Zn(5-chlorouracilato-N(1))(NH(3))(3)].(5-chlorouracilato-N(1)).(H(2)O)

Four new complexes of uracilato and 5-halouracilato with the divalent metal ions Cu(II), Zn(II) and Ni(II) were obtained and structurally characterized. [Cu(uracilato- N(1))(2)(NH(3))(2)].2(H(2)O) (1) and [Cu(5-chlorouracilato-N(1))(2)(NH(3))(2)](H(2)O)(2) (2) complexes present distorted square planar co-ordination geometry around the metal ion. Although an additional axial water molecule is present [Cu(II)-OH(2)=2.89 A (for 1) and 2.52 A (for 2)] in both cases, only in the complex 2 would be considered in the limit of a bond distance. The Zn(II) in [Zn(5-chlorouracilato-N(1))(NH(3))(3)].(5-chlorouracilato-N(1)).(H(2)O) presents a tetrahedral co-ordination with three ammonia molecules and the N(1) of the corresponding uracilato moiety. A non-coordinated uracilato molecule is present as a counterion and a recognition between co-ordinated and free ligands, by means a tandem of H-bonds, should be mentioned. Finally, the complex [Ni(5-chlorouracilato-N(1))(2)(en)(2)] (H(2)O)(2) (where en is ethylenediamine) presents a typical octahedral trans co-ordination with additional hydrogen bonds between 5-chlorouracilato and the NH(2) groups of ethylenediamine units.     

Metal-ion interactions with sugars. Crystal structures and FT-IR studies of the LaCl3-ribopyranose and CeCl3-ribopyranose complexes

Single crystals of LaCl3.C5H10O5.5H2O (1) and CeCl3.C5H10O5.5H2O (2) were obtained from ethanol-water solutions and their structures determined by X-ray. The two complexes are isomorphous. Two configurations of complex 1 or complex 2, as a pair of isomers, were found in each single crystal in a disordered state. The ligand of one of the isomer is alpha-D-ribopyranose in the 4C1 conformation, the ligand of the other is beta-D-ribopyranose in the 1C4 conformation. For complex 1, the alpha:beta anomeric ratio is 51:49, and for complex 2, the ratio is 52:48. Both ligands of the two isomers provide three hydroxyl groups in ax-eq-ax orientation for coordination. The Ln3+ (Ln = La or Ce) ion is nine-coordinated with five Ln-O bonds from water molecules, three Ln-O bonds from hydroxyl groups of the D-ribopyranose, and one Ln-Cl bond from chloride ion. The hydroxyl groups, water molecules, and chloride ions form an extensive hydrogen-bond network. The IR spectral C-C, O-H, C-O, and C-O-H vibrations were observed to be shifted in both the two complexes and the IR results are in accord with those of X-ray diffraction.     

A new family of lanthanide terpyridine nitrate complexes: Solvothermal syntheses, crystal structures and luminescent properties of [Ln(pytpy)(NO3)2(μ-OCH3)]2

The complexes [Ln(pytpy)(NO₃)₂(μ-OCH₃)]₂ (Ln = Eu(III), Tb(III), Dy(III), pytpy=4′-(n-pyridyl)-2,2′:6′,2″-terpyridine, n = 2, 3) were synthesized and characterized by IR, elemental analyses, UV–Vis and luminescent spectroscopy. Three complexes crystallized in monoclinic system, P2₁/n space group. Lanthanide ions are nine-coordinated by three nitrogen atoms from tridentate pytpy ligands, four oxygen atoms from two bidentate nitrate groups and two oxygen atoms from two methoxo groups, forming distorted tricapped trigonal prismatic geometries. The dimethoxo-bridges connect two metal ions in asymmetric fashion into dimeric structures with short LnLn distances of 3.767(1), 3.740(1) and 3.720(1) Å for Eu(III), Tb(III) and Dy(III) complexes, respectively. Photoluminescence measurement indicates that 1 and 3 emit the characteristic luminescence of Tb(III) and Eu(III) ions in the solid state, respectively. The luminescent spectrum of Eu(III) complex in solvents was also investigated.     

Complexation of trivalent lanthanide cations by inositols in the solid state: crystal structure and an FT-IR study of PrCl3.myo-inositol.9 H2O

The title compound, PrCl3.C6H12O6.9 H2O crystallized in the monoclinic space group P2(1)/n with cell dimensions a = 15.8293(3), b = 8.67750(10), c = 16.2292(3) A, beta = 107.0788(8) degrees, V = 2130.92(6) A3 and Z = 4. Each Pr ion is coordinated to nine oxygen atoms, two from the inositol and seven from water molecules, with Pr-O distances from 2.4729 to 2.6899 A; the other two water molecules are hydrogen-bonded. No direct contacts exist between Pr and Cl. There is an extensive network of hydrogen bonds formed by hydroxyl groups, water molecules, and chloride ions. The IR spectra of Pr-, Nd-, and Sm-inositol complexes are similar, which shows that the three metal ions have the same coordination mode. The IR results are consistent with the crystal structure.     

Synthesis,density functional theory calculations and luminescence of lanthanide complexes with 2,6‐bis[(3‐methoxybenzylidene)hydrazinocarbonyl] pyridine Schiff base ligand

A pyridine‐diacylhydrazone Schiff base ligand, L = 2,6‐bis[(3‐methoxy benzylidene)hydrazinocarbonyl]pyridine was prepared and characterized by single crystal X‐ray diffraction. Lanthanide complexes, Ln–L, {[LnL(NO₃)₂]NO₃.xH₂O (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er)} were prepared and characterized by elemental analysis, molar conductance, thermal analysis (TGA/DTGA), mass spectrometry (MS), Fourier transform infra‐red (FT‐IR) and nuclear magnetic resonance (NMR) spectroscopy. Ln–L complexes are isostructural with four binding sites provided by two nitro groups along with four coordination sites for L. Density functional theory (DFT) calculations on L and its cationic [LnL(NO₃)₂]⁺ complexes were carried out at the B3LYP/6–31G(d) level of theory. The FT‐IR vibrational wavenumbers were computed and compared with the experimentally values. The luminescence investigations of L and Ln–L indicated that Tb–L and Eu–L complexes showed the characteristic luminescence of Tb(III) and Eu(III) ions. Ln–L complexes show higher antioxidant activity than the parent L ligand.     

Characterization of lanthanide (III) ion binding to calmodulin using luminescence spectroscopy

Pulsed dye laser excitation spectroscopy of the 7F0----5D0 transition of Eu(III) reveals only a single peak as this ion is titrated into apocalmodulin. A titration based on the intensity of this transition shows that the first two Eu(III) ions bind quantitatively to two tight sites, followed by weaker binding (Kd = 2 microM) to two additional sites under conditions of high ionic strength (0.5 M KC1). This excitation experiment is also shown to be a general method for measuring contaminating levels of EDTA down to 0.2 microM in proton solutions. Experiments with Tb(III) using both direct laser excitation and indirect sensitization of Tb(III) luminescence through tyrosine residues in calmodulin also give evidence for two tight and two weaker binding sites (Kd = 2-3 microM). The indirect sensitization results primarily upon binding to the two weaker sites, implying that Tb(III) binds first to domains I and II, which are remote from tyrosine-containing domains III and IV. The 7F0----5D0 excitation signal of Eu(III) was used to measure the relative overall affinities of the tripositive lanthanide ions, Ln(III), across the series. Ln(III) ions at the end of the series are found to bind more weakly than those at the beginning and middle of the series. Eu(III) excited-state lifetime measurements in H2O and D2O reveal that two water molecules are coordinated to the Eu(III) at each of the four metal ion binding sites. Measurements of F?rster-type nonradiative energy-transfer efficiencies between Eu(III) and Nd(III) in the two tight sites were carried out by monitoring the excited-state lifetimes of Eu(III) in the presence and absence of the energy acceptor ion Nd(III).(ABSTRACT TRUNCATED AT 250 WORDS)     

Chemiluminescence and energy transfer mechanism of lanthanide ions in different media based on peroxomonosulfate system

The chemiluminescence (CL) phenomena of lanthanide (Ln) ions and their coordinate complexes in peroxomonosulfate system and the energy transfer mechanism during the process were investigated in this work. A strong and sharp CL signal was yielded when the Eu(III) or Tb(III) solution was added to the peroxymonosulfate solution. The CL intensity was greatly enhanced by 2,6‐pyridinedicarboxylic acid (DPA) ligand [maximum enhancement reached when Ln(III):DPA was 1:1] and hexadecyltrimethylammonium chloride micelles. The degree of enhancement of DPA and micelles on Ln(III) CL was related to the fluorescence lifetimes of Ln(III) in different media. According to the ESR spin‐trapping experiments of 2,2,6,6‐tetramethyl‐4‐piperidone and the specific quenching experiments of 1,4‐diazabicyclo[2.2.2]octane and sodium azide, singlet oxygen was generated though the Ln(III) ion‐catalyzed decomposition of peroxymonosulfate. From the comparisons of the fluorescence and CL spectra, lanthanide ions were the luminescence emitter and the ligand DPA absorbed the energy from singlet oxygen and transferred it to Ln(III) ions in the coordinate complexes. Micelles can enhance the CL intensity by improving intermolecular energy transfer efficiencies, removing the quenching effect of water and prolonging the lifetime of singlet oxygen. Copyright © 2009 John Wiley & Sons, Ltd.     

Diethyl and diisopropyl phosphite complexes of lanthanide(III) chlorides

Lanthanide chlorides form adducts of the type [Ln(L)_nCl₃] (where Ln = La, Pr, Nd, Sm, Eu, when n = 6; and Ln = Gd, Tb, Dy or Yb when n = 5; and L = (EtO)₂P(O)H or (PrⁱO)₂P(O)H upon interacting with the diethyl and diisopropyl phosphites in dry ethyl and isopropyl alcohol, respectively. Complexes were recrystallised from ethanol or isopropanol and washed with n-hexane. On the basis of elemental analysis, infrared, ¹H NMR and ³¹P NMR spectral studies, it is concluded that these phosphites coordinate to the lanthanide metal atom through the oxygen atom which has the greatest affinity for lanthanides in these adducts.     

Chiroptical Spectra of Tetrakis (+)‐3‐Heptafluorobutylrylcamphorate Ln(III) Complexes with an Encapsulated Alkali Metal Ion: Solution Structures as Revealed by Chiroptical Spectra

The preparation of tetrakis((+)‐hfbc) lanthanide(III) complexes with an encapsulated alkali metal and ammonium ions M[Ln((+)‐hfbc)₄] (hereafter abbreviated as M‐Ln : (+)‐hfbc, (+)‐heptafluorobutyrylcamphorate; M, ammonium or benzyl ammonium ions as well as alkali metal ions) was reported and discussed. The electronic circular dichroism (CD) spectra in the intraligand π?π* transition of M–Ln were examined in view of the solvent effect. Here, the concentration, alkali metal, and ammonium ion dependences are compared with the solid CD, ⁵D₀ ← ⁷F₀(Eu(III)) excitation spectra, circularly polarized luminescence, and vibrational circular dichroism. It has been revealed that the dodecahedral eight coordinate DD‐8‐M‐Ln complexes in crystals are equilibrated between the diastereoselectively formed square antiprism eight coordinate SAPR‐8‐M‐Ln and [Ln((+)‐hfbc)₃] in EtOH and CH₃CN solutions or between the SAPR‐8‐M‐Ln and DD‐D_2d(mmmm)‐8‐M‐Ln complexes in CHCl₃ solution. The observed CD couplets are found to reflect the exciton CD couplets which are useful to determine the four‐bladed SAPR‐(llll) absolute configuration around the lanthanide(III) ion. Chirality 24:1055–1062, 2012. © 2012 Wiley Periodicals, Inc.     

Complexation of trivalent lanthanide cations by erythritol in the solid state. The crystal structure and FT-IR study of 2EuCl3.2C4H10O4.7H2O

Erythritol was chosen to study the interactions between metal ions and carbohydrates. FTIR spectroscopy results indicate that a EuCl3-erythritol complex different from a previously reported one was obtained. The crystal structure of EuCl3-erythritol complex, 2EuCl3.2C4H10O4.7H2O, Mr=443.49, a=13.846(3) A , b=7.4983(15) A, c=14.140(3) A, beta=116.39(3) degrees, V=1315.1(5) A(3), Z=4, mu=5.394 mm(-1) and R=0.0395 for 2965 observed reflections and 143 parameters, was determined. Characteristic of this complex is the presence of binuclear europium ions with different coordination structures. One Eu3+ ion is nine-coordinated, with five Eu-O bonds from water molecules, and four from hydroxyl groups of two erythritol molecules and another Eu3+ is eight-coordinated with two water molecules, two chloride ions, and four hydroxyl groups from two erythritol molecules. Erythritol provides two hydroxyl groups to one lanthanide ion and the other two to another rare earth ion. The OH, CO stretching and other vibrations are shifted in the IR spectra of the complexes and the results are consistent with the crystal structure.     

Synthesis, antimicrobial activity and chemotherapeutic potential of inorganic derivatives of 2-(4'-thiazolyl)benzimidazole[thiabendazole]: X-ray crystal structures of [Cu(TBZH)2Cl]Cl.H2O.EtOH and TBZH2NO3 (TBZH=thiabendazole)

Thiabendazole (TBZH) reacts with iron(III) nitrate causing protonation of the ligand to yield the nitrate salt [TBZH(2)NO(3)] (1). Reaction of TBZH with copper(II) acetate results in the deprotonation of the ligand yielding [Cu(TBZ)2.(H2O)2] (2). Reactions of TBZH with the chloride, nitrate and butanedioate salts of copper(II) yields [Cu(TBZH)2Cl]Cl.H2O.EtOH (3), [Cu(TBZH)(2)(NO(3))(2)] (4) and [Cu(TBZH)(O(2)C-CH(2)CH(2)-CO(2))] (5), respectively. The TBZH acts as a neutral chelating ligand in 3-5. Molecular structures of 1 and 3 were determined crystallographically. In 1, the asymmetric unit contains one TBZH(2)(+) cation and one NO(3)(-) anion. The structure of 3 comprises a five coordinate copper centre with the metal bound to two chelating TBZH ligands and one chloride. The geometry is best described as trigonal bipyramidal. Hydrogen bonding connects the complex cation with the uncoordinated chloride anion and the water and ethanol solvate molecules. Compound 1 and the copper complexes 2-5, the metal free ligands and a number of simple copper(II) salts were each tested for their ability to inhibit the growth of Candida albicans. The metal free TBZH and its nitrate salt (1) exhibited very poor activity. Complex 2, in which the TBZH is present as an anionic ligand (TBZ(-)), exhibits moderate activity towards the pathogen. Chelation of the neutral TBZH to copper centres (complexes 3-5) results in potent anti-candida activity. The dimethyl sulphoxide (DMSO) soluble complexes 3 and 4, along with metal free TBZH were assessed for their cancer chemotherapeutic potential towards two human epithelial-derived cancer model cell lines. Complexes 3 and 4 displayed similar dose-dependent cytotoxicity in both cell lines with IC(50) values of approximately 50 microM, which were found to be significantly lower than that for metal free TBZH.     

Synthesis, inhibitory activity and molecular docking studies of two Cu(II) complexes against Helicobacter pylori urease

Two mononuclear copper(II) complexes, [Cu(C(15)H(16)NO(2))(2)] (1) and [Cu(C(6)H(9)N(2)O(4))(2)·3H(2)O] (2·3H(2)O), were synthesised and structurally characterised by single-crystal X-ray analysis. The copper(II) atom adopts a square-planar environment in complex 1, while the geometry in 2·3H(2)O could be described as the distorted square pyramidal. Complexes 1 and 2·3H(2)O were evaluated for their inhibitory activities against Helicobacter pylori (H. pylori) urease in vitro. They both were found to have strong inhibitory activities against H. pylori urease comparable to that of acetohydroxamic acid (AHA). A docking simulation was performed to position 2 into the H. pylori urease active site to determine the probable binding conformation.