Copper(II) complexes with uridine,uridine 5'-monophosphate,spermidine, or spermine in aqueous solution

Molecular complexes of the types (Urd)H(x)(PA) and (UMP)H(x)(PA) are formed in the uridine (Urd) or uridine 5'-monophosphate (UMP) plus spermidine or spermine systems, as shown by the results of equilibrium and spectral studies. Overall stability constants of the adducts and equilibrium constants of their formation have been determined. An increase in the efficiency of the reaction between the bioligands is observed with increasing length of the polyamine. The pH range of adduct formation is found to coincide with that in which the polyamine is protonated while uridine or its monophosphate is deprotonated. The -NH(x)(+) groups from PA and the N(3) atom of the purine base as well as phosphate groups from the nucleotides have been identified as the significant centres of non-covalent interactions. Compared to cytidine, the pH range of Urd adduct formation is shifted significantly higher due to differences in the protonation constants of the endocyclic N(3) donor atoms of particular nucleosides. Overall stability constants of the Cu(II) complexes with uridine and uridine 5'-monophosphate in ternary systems with spermidine or spermine have been determined. It has been found from spectral data that in the Cu(II) ternary complexes with nucleosides and polyamines the reaction of metallation involves mainly N(3) atoms from the pyrimidine bases, as well as the amine groups of PA. This unexpected type of interaction has been evidenced in the coordination mode of the complexes forming in the Cu-UMP systems including spermidine or spermine. Results of spectral and equilibrium studies indicate that the phosphate groups taking part in metallation are at the same time involved in non-covalent interaction with the protonated polyamine.     

Iminodiacetyl-hydroxamate derivatives as metalloproteinase inhibitors: equilibrium complexation studies with Cu(II), Zn(II) and Ni(II)

Two new iminodiacetyl-hydroxamate derivatives, the N-benzyl-N-carboxymethyl-iminoacetohydroxamic acid (H(2)L(1)) and the N-benzyl-N'-hydroxypiperazine-2,6-dione (HL(2)), have been recently reported as very effective inhibitors against a set of zinc-containing matrix metalloproteinases (MMPs). Herein, aimed at understanding that inhibitory function, these compounds are studied in their complex formation equilibria with three biologically relevant first-row transition M(2+) metal ions (M=Cu, Zn, Ni) by using potentiometric and spectroscopic techniques. At physiological conditions, complexation of these metal ions by H(2)L(1) mostly occurs with formation of 1:1 species by tridentate co-ordination (O,N,N) (carboxylate-amino-hydroxamate), whereas complexation with HL(2) mainly involves the formation of 1:2 (M:L) species with normal (O,O) hydroxamate coordination. Moreover, at higher pH, H(2)L(1) is able to form a pentanuclear tetrameric copper complex with an interesting 12-metallacrown-4 structure.     

Some new derivatives of organozirconium(IV) and organotitanium(IV) with thiophenecarboxylic acids

The complexes of the type Cp₂M(3-TC)Cl, Cp₂M(3-TC)₂, Cp₂M(3-TA)Cl, Cp₂M(3-TA)₂, Cp₂M(2-TB)Cl, Cp₂M(2-TB)₂ [where Cp = cyclopentadienyl, M = Zr or Ti] were synthesized by the reactions of dichlorobis(cyclopentadienyl)zirconium(IV) and dichlorobis(cyclopentadienyl)titanium(IV) with 3-thiophenecarboxylic acid (3-TCH), 3-thiopheneacetic acid (3-TAH) and 2-thiophenebutyric acid (2-TBH) respectively in different stoichiometric ratios. The new complexes were characterized by their elemental analysis, ¹H NMR, IR, and electronic spectral data.     

Complexes of Ni(II) and Cu(II) with ofloxacin. Crystal structure of a new Cu(II) ofloxacin complex

Several coordination compounds formed between Ni(II) or Cu(II) with ofloxacin have been synthesised and characterised. According to elemental chemical analysis and FT-IR spectroscopy data, direct reaction of Ni(II) and Cu(II) salts with ofloxacin leads to formation of precipitates for which mass spectrometry demonstrates their polymeric nature. However, crystalline [Cu(oflo)2(H2O)].2H2O is formed if the reaction is carried out in the presence of ammonia. This complex crystallises in the triclinic system, space group P-1 with a=9.2887(12), b=11.2376(14), c=17.874(2) A, alpha=92.12(3), beta=95.39(3), gamma=91.71(3) degrees and Z=2. The local geometry around the Cu(II) ion is a slightly distorted square base pyramid. Electronic spectra, magnetic susceptibility measurements and EPR spectra of the synthesised complexes indicate a tetragonal environment.     

Ni(II) and Ni(I) forms of pentaalkylamide derivatives of cofactor F430 of Methanobacterium thermoautotrophicum.

A series of pentaalkylamide forms of F430 and of its 12,13-diepimer have been generated and characterized. Carbodiimide-assisted N-hydroxysulfosuccinimide activation of all five peripheral carboxylates of the F430 macrocycle allows nucleophilic attack by a number of primary amines (RNH2, R- = CH3-, CH3CH2-, CF3CH2-, CH3(CH2)3-) generating the pentaalkylamide derivatives. The identity of each derivative has been verified by fast-atom bombardment mass spectrometry (FAB-MS). The solubility of these derivatives in aprotic organic solvents varies as the amine alkyl substituent (R-) is changed. Electrochemical measurements have shown that the Ni(II/I) reduction potentials in N,N-dimethylformamide (DMF) are approximately -1 V (Ag/AgCl). Reduction by sodium amalgam in THF generates the Ni(I) form of the F430 diepimer pentabutylamide. The visible and EPR spectra of this Ni(I) species are very similar to the corresponding spectra of Ni(I) F430M (Jaun, B. and Pfaltz, A. (1986) J. Chem. Soc. Chem. Commun. 1327-1329.).     

Thermodynamic and spectroscopic studies of Cu(II) and Ni(II) complexes with a new proline-threonine dipeptide ligand

The interactions between a new proline-threonine dipeptide ligand with two metallic cations were investigated in aqueous solution. The metallic cations studied were the copper(II) and the nickel(II), which are involved in many biological processes. The combination of potentiometry, UV-visible spectrophotometry, EPR, and mass spectrometry was used to determine the formation constants of the complexes and their structure in solution. The complexation sites were identified using electronic absorption and EPR spectroscopies. Copper complexes were obtained as square planar or square pyramidal mononuclear species, whereas nickel complexes were obtained as dinuclear species with an octahedral geometry.     

Chromium(III) interactions with nucleotides. II

New derivatives were obtained from Cr(urea)₆Cl₃· 3H₂O in an ethyl acetate medium of chromium(III) with uracil, uridine, 5′UMP, 5′CMP, 5′GMP and 5′IMP. The new derivatives were characterized by elemental analysis, electronic and infrared spectroscopy and thermal analysis. These derivatives proved to be outer sphere complexes, in which the nucleotide, the nucleoside or the base interacts with the starting complex through intramolecular hydrogen bonding.Cr(XMP)(OH)·3H₂O (XMP: 5′UMP, 5′CMP, 5′GMP and 5′IMP) complexes were obtained by hydrolysis of the above derivatives of the nucleotides. In these reactions there is a total substitution of the urea molecules. The derivatives obtained by hydrolysis were characterized in solid state by electronic and infrared spectroscopy. These results provide more insight into the biological role of chromium.     

Coordination chemistry of two new tetraaza Ni(II) and Cu(II) macrocyclic and two new Co(II) and Zn(II) macroacyclic Schiff base complexes containing piperazine moiety: X-ray crystal structures of Ni(II) and Zn(II) complexes

A new potentially tetradentate (N₄) Schiff base ligand (L), 1,9,12,20-tetraazatetracyclo[18.2.2.02,7.014,19]tetracosa-2(7),3,5,8,12,14(19),15,17-octaene containing a piperazine moiety is described. Macrocyclic Schiff base complexes, [NiL](ClO₄)₂ (1) and [CuL](ClO₄)₂ (2) have been obtained from equimolar amounts of ligand (L) with nickel(II) and copper(II) metal ions. While the equilibrium reaction in the presence of cobalt(II) and zinc(II) metal ions with ligand L in a 1:1 molar ratio yielded the open-chain Schiff base complexes, [CoL′](ClO₄)₂ (3) and [ZnL′](ClO₄)₂ (4) containing two terminal primary amino groups. The ligand L′ is 1,4-bis(2-(2-aminoethyliminomethyl)phenyl)piperazine. The crystal structures of (1) and (4) have been also determined by X-ray diffraction. It was shown that the Ni(II) is coordinated to the ligand L by two nitrogen atoms of piperazine group and two nitrogen atoms of the imine groups, in a slightly distorted square-planar geometry. Also single crystal X-ray analysis of (4) confirmed a distorted octahedral arrangement in the vicinity of Zn atom with N₆ donor set. The spectroscopic characterization of all complexes is consistent with their crystal structures.     

Structure and antimicrobial activity of some new azopyrazolone chelates of Ni(II) and Cu(II) acetates, sulfates, and nitrates

Four coordinate Ni(II) and Cu(II) chelates formed by reaction of two azopyrazolone derivatives with metal sulfate, acetate, or nitrate are described. It is concluded that the ligands possess tautomeric equilibria and can coordinate to the metal ion as neutral or monobasic bidentates. The so-obtained complexes are characterized by elemental and thermal analyses, IR and electronic spectra, as well as conductivity measurements. A pseudo-tetrahedral polymeric structure is proposed for all the complexes in which the acetate, nitrate, or sulfate is attached to the metal ion in the bridging bidentate mode. It is observed that the chelates formed are more potent as antimicrobial agents than the free ligands.     

Synthesis, crystal structures and properties of substituted-pyridyl functionalized bis(ethylenedithio)tetrathiafulvalene derivatives and their corresponding Ni(II) and Co(II) complexes

Three substituted-pyridyl functionalized bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) derivatives 1-3 and their corresponding Ni(II) and Co(II) complexes have been synthesized and characterized. Their electrochemical properties in CH₂Cl₂ solution have been investigated by cyclic voltammetry and two reversible single-electron oxidation waves for the TTF moiety are observed. Crystal structure analyses were carried out for compound 2 as well as for the Co(II) complex of 1 (7).     

Synthesis of new uracil derivatives and their sugar hydrazones with potent antimicrobial,antioxidant and anticancer activities

Abstract

6-(4-Chloro-3-nitrophenyl)-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitrile (4) was prepared and was reacted with ethyl chloroacetate, hydrazine hydrate, 4-chloroaniline, formaldehyde, acetic anhydride, formic acid, carbon disulfide, 4-cyanobenzaldehyde, triethyl orthoformate, D-sugars, 4-aminoacetophenone, benzoyl choride and cyclohexanone to afford a series of new uracil derivatives (5–18). Examination of some of the prepared compounds for their antimicrobial, antioxidant and anticancer activities was conducted. Among the tested samples, compound 17 was the most active substance against the gram-positive bacteria and was more potent than the reference drug Cefoperazone. Moreover, the antibacterial activity of 17 was higher against gram-negative bacteria. Compounds 6 and 13 reached a higher scavenging ability toward DPPH radicals and are better candidates for antioxidant activity. Also, compounds 6 and 13 had no significant anticancer activity toward liver cancer (Hep G2) and breast cancer (MCF-7) cell lines.     

Ru(II) complexes with new redox-active 1,10-phenanthroline derivatives: structural, spectral, and electrochemical investigations

New 1,10-phenanthroline derivatives bearing diarylamino and heteroaromatic moieties in the 3,8-position have been prepared by a palladium-catalyzed C-N bond formation reaction. Formation of Ru(II) complexes with the chelating ligands and their photophysical and electrochemical redox properties have been examined.     

Synthesis, characterization and antibacterial activity of new sulfonamide derivatives and their nickel(II), cobalt(II) complexes

Methanesulfonicacid hydrazide (a sulfonamide compound, msh: CH₃SO₂NHNH₂) derivatives: methylsalicylaldehydemethanesulfonylhydrazone (5msalmsh), 5-methyl-2-hydroxyaceto-phenonemethanesulfonylhydrazone (5mafmsh) and their Ni(II), Co(II) complexes have been synthesized for the first time. The structure of these sulfonamide compounds has been investigated by using elemental analyses; FT-IR, ¹H NMR, ¹³C NMR, LC-MS, and UV-Vis spectrometric methods; magnetic susceptibility; conductivity measurements; thermal studies. The crystal structure of 5msalmsh has been investigated by X-ray analysis. The antibacterial activities of synthesized compounds were studied against gram positive bacteria: Staphylococcus aureus, Bacillus subtilis, and Bacillus magaterium; and gram negative bacteria: Salmonella enteritidis, and Escherichia coli by using the microdilution broth method. The biological activity screening showed that ligands have more activity than complexes against the tested bacteria.     

Dinuclear Ni(II) and Cu(II) complexes with indolecarboxamide ligand: Synthesis, structure and properties

A potential tetradentate indolecarboxamide ligand, H₄L³ is synthesized and investigated for its coordination abilities towards Ni(II) and Cu(II) ions. Two H₄L³ ligands in their tetra-deprotonated form [L³]⁴⁻, were found to coordinate two metal centers resulting in the formation of [Ni₂(L³)₂]⁴⁻ (5) and [Cu₂(L³)₂]⁴⁻ (6) complexes. The crystal structure of 6 displays the formation of a dinuclear structure where two fully deprotonated ligands, [L³]⁴⁻ hold two copper(II) ions together. Even more interesting is the fact that both deprotonated ligands, [L³]⁴⁻ coordinate the copper ions in an identical and symmetrical fashion. The Na⁺ cations present in the complex 6 stitch together the dinuclear units resulting in the formation of a coordination chain polymer. Four sodium ions connect two dinuclear units via interacting with the O_amide groups. Further, Na⁺ cations were found to coordinate several DMF molecules; some of them are terminal and a few are bridging in nature. The solution state structure (determined by the NMR spectral analysis) of the diamagnetic complex 5 also supported the fact that two deprotonated ligands, coordinate two nickel ions in an identical and symmetrical fashion. Absorption spectral studies reveal that the solid-state square-planar geometry is retained in solution and both complexes do not show any tendency to coordinate potential axial ligands. The variable-temperature magnetic measurements and EPR spectra indicate spin-spin exchange between two copper centers in complex 6. The electrochemical results for both complexes show three irreversible oxidative responses that correspond to the oxidation of first and second metal ion followed by the ligand oxidation, respectively.     

Acetazolamide-M(II) [M(II) = Co(II),Ni(II),Cu(II)] complexes with ethylamine, diethylamine, triethylamine, and potassium hidroxide

Complexes of Co(II), Ni(II), and Cu(II) with dideprotonated Acm are synthesized and characterized. Acm acts as bidentate ligand through the N-sulfonamido atom and the N-thiadiazole atom except for K6CoAcm4.6H2O in which Acm behaves as monodentate through the N-sulfonamido atom.