55 research outputs found
Koordinációs viszonyok és konformációs egyensúlyok vizsgálata aliciklusos beta-aminosav származékok réz(II) komplexeinél kétdimenziós ESR spektroszkópiai módszerrel = Study of conformational equilibrium and coordinational modes of alicyclic beta-aminoacid derivatives- copper(II) complexes by two-dimensional ESR method
Az Elektronspin Rezonancia SpektroszkĂłpia (ESR) mĂłdszerĂ©t alkalmaztuk rĂ©z(II)-bioligandum komplexek oldategyensĂşlyi Ă©s szerkezetvizsgálatára. Meghatároztuk az oldatban (2-12-es pH tartományban, szobahĹ‘mĂ©rsĂ©kleten) kĂ©pzĹ‘dĹ‘ komplexek összetĂ©telĂ©t Ă©s kĂ©pzĹ‘dĂ©si állandĂłikat valamint javaslatot tettĂĽnk az egyes komplexek szerkezetĂ©re. NĂ©gy vegyĂĽletcsalád segĂtsĂ©gĂ©vel megvizsgáltunk kĂĽlönbözĹ‘, a ligandumok komplexkĂ©pzĂ©sĂ©t befolyásolĂł tĂ©nyezĹ‘ket, mint a geometriai Ă©s szerkezeti izomĂ©ria, illetve szubsztituens hatás, Ă©s megállapĂtottuk, hogy ezek a tĂ©nyezĹ‘k jelentĹ‘sen befolyásolták a komplexkĂ©pzĂ©s erĹ‘ssĂ©gĂ©t. Az (1) aliciklusos-beta-aminosavak L-Phe származĂ©kainál a cisz- Ă©s transz- sztereoizomerek közĂĽl a cisz- (2) a tioszemikarbazon vegyĂĽletek esetĂ©n az amino vĂ©gen metilezett származĂ©kok, (3) a 3-,4-,5-,6- pozĂciĂłban fluorozott szalicilsavak közĂĽl a 3-fluoro-szalicilsav (4) a hisztidineket tartalmazĂł oligopeptidek esetĂ©n a szabad amino vĂ©get tartalmazĂł aminosav a tBoc-csoporttal vĂ©dett párjával szemben mutatot jelentĹ‘sen erĹ‘sebb komplexkĂ©pzĹ‘ hatást. Mivel a vizsgált vegyĂĽletek Ă©s azok rĂ©z(II)komplexei is biolĂłgiai aktĂvitással rendelkeznek, a komplexkĂ©pzĂ©s erĹ‘ssĂ©gĂ©t befolyásolĂł tĂ©nyezĹ‘k ismerete a kĂ©sĹ‘bbiekben a gyĂłgyszerkutatás számára adhat fontos informáciĂłkat. | Electronspin resonance spectroscopy (EPR) have been used for the solution equilibrium and coordination study of copper(II)-bioligand complexes.We could determine the constitution and formation constants of the species formed in solution (between pH 2-12, at room temperature) and we proposed a structure for each complexes. By the help of four different groups of compounds, the influence of conformation and geometry isomerization and substituent effect have been studied. We have concluded that these factors had major impact on the complexation ability of the ligands. Stronger complex formation have been found for (1) cis than for trans stereoizomers of alicyclic-beta-aminoacid L-Phe derivatives (2) for the N-terminally dimethylated derivatives of thiosemicarbazones against the non-methylated ones (3) for 3-fluorosalicylic acid among 3-,4-,5-,6-fluorosalicylic acids (4) and in case of histidine containing peptides for the non tBoc-protected peptides. Owing to the biological activity of the above ligands and their complexes our results may be beneficial for drug researchers
A katalitikus aktivitás csökkenését okozó fizikai- és kémiai átalakulások vizsgálata "vas oxidot" tartalmazó heterogén katalizátoroknál = Investigation of the physical and chemical influences leading to catalyst fouling in the case of iron oxide content heterogeneous catalysts
A T 048769 számĂş OTKA tĂ©ma feladata az volt, hogy i) hőállĂł mezopĂłrusos szilika katalizátor hordozĂłt kĂ©szĂtsen (szĂ©n-) nanocsĹ‘ szintĂ©zishez; ii) mĂ©rsĂ©kelten nagy fajlagos felĂĽletű hordozĂłt állĂtson elĹ‘, melyre a számos vas oxid mĂłdosulat közĂĽl a benzol szelektĂv katalitikus oxidáciĂłjában legaktĂvabbnak vĂ©lt ferrihidrit, magnetit, maghemit Ă©s hematit leválaszthatĂł, Mössbauer- Ă©s ESR spektruma tanulmányozhatĂł Ă©s aktivitása tesztelhetĹ‘. A legfontosabb megállapĂtások, ad i): VĂzĂĽveg kiindulási anyagot használva Si forráskĂ©nt alkálikus közegben nem alakul ki hexagonális szilika szerkezet. A (keverĂ©stĹ‘l fĂĽggĹ‘en) 2-30 µm-es szemcsĂ©k 15-20 nm-es SiO2-gĂ©l Ă©s kristályos SiO2 mĂłdosulatok (β-tridimit Ă©s kvarc) rendezetlen halmazábĂłl állnak. TEOS adagolásával a vĂzĂĽveg ortoszilikát összetevĹ‘je növelhetĹ‘, ami elĹ‘segĂti a hexagonális rendezĹ‘dĂ©st. A vizsgálatok más megvilágĂtásba helyeztĂ©k a felhasznált felĂĽletaktĂv anyagok ("surfactants") Ă©s a szilikát összetevĹ‘ kölcsönhatását. Ad ii): A felsorolt vas oxid-fĂ©lesĂ©gek ESR spektrumait számĂtĂłgĂ©ppel összetevĹ‘ikre felbontva ("dekonvolĂşciĂł") a Mössbauer spektrumokban sikerĂĽlt megtalálni ugyanezeket az összetevĹ‘ket, Ăgy az Ar elĹ‘fordulási gyakoriságok segĂtsĂ©gĂ©vel becsĂĽlhetĹ‘vĂ© váltak az ESR átmeneti valĂłszĂnűsĂ©gek. A minták aktivitásának tesztelĂ©se arra a furcsa (de nem meglepĹ‘) eredmĂ©nyre vezetett, hogy a minták katalitikus aktivitását ferrihidrit tartalmuk Ă©s/vagy a rácshibák gyakorisága határozza meg. | The OTKA project No. T 048769 was aiming to solve two well defined tasks: i) to synthesize a catalyst carrier ('silica') exhibiting mezoporous structure and having high thermal/hydrothermal stability in (carbon) nanotube synthesis; ii). to prepare another carrier onto various iron oxide polymorphs (like ferrihydrite, magnetite, maghemite and hematite) can be deposited. The Mössbauer- and EPR spectra of these samples should be registered and their activities tested in the selective catalytic oxidation of benzene. Referring to i): it has been found that using water-glass as Si source the silica grains in 2-30 µm size are agglomerates of very little (15-20 nm) hydrated amorphous and crystalline (β-tridymite and quartz) SiO2 particles in random arrangement. Modifying the orthosilicic content of the water-glass by admixing TEOS, the degree of hexagonal ordering can be influenced. Ad ii): PC deconvolution of the EPR spectra permitted to estimate the EPR transition probabilities by comparing the relevant spectral pairs in the Mössbauer and EPR spectra. The testing of activities revealed that the catalytic activities were depending on the ferrihydrite content of the various samples and/or the probabilities of structural defects
Complexation properties of oligopeptide H-GHKHG-H with copper(II) studied by the decomposition of electron paramagnetic resonance spectra
The solvation and redox behavior of mixed ligand copper(II) complexes of acetylacetonate and aromatic diimines in ionic liquids
The behavior of two cationic copper complexes of acetylacetonate and 2,2'-bipyridine or 1,10-phenanthroline, [Cu(acac)(bipy)]Cl (1) and [Cu(acac)(phen)]Cl (2), in organic solvents and ionic liquids, was studied by spectroscopic and electrochemical techniques. Both complexes showed solvatochromism in ionic liquids although no correlation with solvent parameters could be obtained. By EPR spectroscopy rhombic spectra with well-resolved superhyperfine structure were obtained in most ionic liquids. The spin Hamiltonian parameters suggest a square pyramidal geometry with coordination of the ionic liquid anion. The redox properties of the complexes were investigated by cyclic voltammetry at a Pt electrode (d = 1 mm) in bmimBF(4) and bmimNTf(2) ionic liquids. Both complexes 1 and 2 are electrochemically reduced in these ionic media at more negative potentials than when using organic solvents. This is in agreement with the EPR characterization, which shows lower A(z) and higher g(z) values for the complexes dissolved in ionic liquids, than in organic solvents, due to higher electron density at the copper center. The anion basicity order obtained by EPR is NTf2-, N(CN)(2)(-), MeSO4- and Me2PO4-, which agrees with previous determinations. (C) 2013 Elsevier B.V. All rights reserved
Two hydroxy pyridinecarboxylic acid derivatives as a possible chelating agents in neurodegenerative disease; equilibrium complexation studies with Cu(II), Zn(II).
The metal ion chelators 4-hydroxy-5-methyl-3-pyridinecarboxylic acid (DQ5) and 1,5-dimethyl-4-hydroxy-3-pyridinecarboxylic acid (DQ715) and Cu(II) and Zn(II) were investigated with the aim to restore the homeostasis of the brain Cu(II) and Zn(II) in neurodegenerative diseases. The proton dissociation constants of the ligands, the stability constants, and the coordination modes of the metal complexes formed were determined by pH-potentiometric, and spectral (UV–Vis and EPR or 1H NMR) methods. The results show that in slightly acidic and neutral pH range mono and bis complexes are formed through bidentate coordination of the ligands. The biological MTT-test reveals that the DQ715 ligand is able to lower the cytotoxic effect of Cu(II) in human embryonic kidney HEK-293 cells. Our studies revealed, however, that none of the chelators were efficient enough to withdraw these metal ions from the amyloid aggregates
The solvation and electrochemical behavior of copper acetylacetonate complexes in ionic liquids
The behavior of copper(II) complexes of pentane-2,4-dione and 1,1,1,5,5,5-hexafluoro-2,4-pentanedione, [Cu(acac)(2) (1) and [Cu(HFacac)(2)(H2O)] (2), in ionic liquids and molecular organic solvents, was studied by spectroscopic and electrochemical techniques.
The electron paramagnetic resonance characterization (EPR) showed well-resolved spectra in most solvents. In general the EPR spectra of [Cu(acac)(2)] show higher g(z) values and lower hyperfine coupling constants, A(z), in ionic liquids than in organic solvents, in agreement with longer Cu-O bond lengths and higher electron charge in the copper ion in the ionic liquids, suggesting coordination of the ionic liquid anions. For [Cu(HFacac)(2)(H2O)] the opposite was observed suggesting that in ionic liquids there is no coordination of the anions and that the complex is tetrahedrically distorted.
The redox properties of the Cu(II) complexes were investigated by cyclic voltammetry (CV) at a Pt electrode (d = 1 mm), in bmimBF(4) and bmimNTf(2) ionic liquids and, for comparative purposes, in neat organic solvents. The neutral copper(II) complexes undergo irreversible reductions to Cu(I) and Cu(0) species in both ILs and common organic solvents (CH2Cl2 or acetonitrile), but, in ILs, they are usually more easier to reduce (less cathodic reduction potential) than in the organic solvents. Moreover, 1 and 2 are easier to reduce in bmimNTf(2) than in bmimBF(4) ionic liquid. (C) 2013 Elsevier B.V. All rights reserved
Intercalation and coordination of copper(II)-2,2′-bipyridine complexes into graphite oxide
Copper-intercalated graphite oxides (GO) were prepared by adding complex solutions of cupric ions and 2,2′-bipyridine (L) ligands to exfoliated GO dispersion at pH = 7. High adsorption capacity (>140 mg Cu/g GO) was found for adsorption from equimolar solution of Cu2+ and L, while the excess of ligand results in progressively decreasing adsorbed amounts. Electron paramagnetic resonance spectra revealed two principal adsorption mechanisms: the CuL3 2 + complex undergoes ion exchange adsorption, while CuL2+ and CuL2 2 + bind to graphene oxide layers by coordination. © 2014 Elsevier Ltd. All rights reserved
Complexes of pyridoxal thiosemicarbazones formed with vanadium(IV/V) and copper(II): solution equilibrium and structure
L- and D-proline thiosemicarbazone conjugates: coordination behavior in solution, and the effect of copper(II) coordination on their antiproliferative activity
A comparative study of α-N-pyridyl thiosemicarbazones: spectroscopic properties, solution stability and copper(II) complexation
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