Proton- and lanthanide-coordinating properties of the tetraaza macrocycle (EDDA-KA)2 in aqueous solution

2001 ◽  
Vol 79 (5-6) ◽  
pp. 1058-1067 ◽  
Author(s):  
Bin Song ◽  
Glen S Kurokawa ◽  
Shuang Liu ◽  
Chris Orvig
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Bonding ◽  
Stability Constants ◽  
Metal Ion ◽  
Lanthanide Ions ◽  
Distribution Diagram ◽  
Pyrone Ring ◽  
H Nmr ◽  
Species Distribution Diagram ◽  
Nmr Titrations

The new potentially multidentate ligand (EDDA-KA)2 has been prepared and its acid-base properties determined. Its coordination properties with three lanthanide ions (La3+, Gd3+, and Lu3+) and Fe3+ have been studied in aqueous solution (I = 0.16 M NaCl, 25°C) by potentiometric pH, spectrophotometric, and 1H NMR titrations. In total, eight pKa values could be determined by these diverse methods. From the 1H NMR titrations, all the deprotonation steps could be determined and assigned (in groups). Strong hydrogen bonding among two nitrogen atoms and one oxygen atom on the pyrone ring was observed, and the corresponding pKa values were estimated to be 13.2 and 14.0. By comparison with similar systems, an equilibrium constant for the formation of the hydrogen bond was estimated, KI = 104.4. Eight stability constants in total were determined for various protonation states of the La3+ and Gd3+ complexes, but for Lu3+ only the last four constants were obtained. The species distribution diagram showed that [M(EDDA-KA)2-4H]2- predominated in the range 5 [Formula: see text] pH [Formula: see text] 9 and [M(EDDA-KA)2-6H]4- predominated in the region 9 [Formula: see text] pH [Formula: see text] 11. In the former complex, two strong hydrogen bonds anchored the macrocycle and Ln3+ was coordinated with the four carboxylate groups; in the latter, the two hydrogen bonding protons were absent and the metal ion might also bind to the nitrogens on the macrocycle. The stability of Gd3+-(EDDA-KA)2 is lower than the analogous Gd3+ complexes of DOTA, DTPA, and DTPA-BMA.Key words: acidity constants, stability constants, La3+, Gd3+, Lu3+, Fe3+, amino carboxylate chelator.

scholarly journals Interaction of Ampicillin and Amoxicillin with Mn2+: A Speciation Study in Aqueous Solution

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3110
Author(s):  
Claudia Foti ◽  
Ottavia Giuffrè
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Metal Ion ◽  
Formation Constants ◽  
Enthalpy Change ◽  
Ligand Concentration ◽  
Empirical Parameter ◽  
Speciation Study ◽  
Potentiometric Measurements ◽  
The Stability

A potentiometric and UV spectrophotometric investigation on Mn2+-ampicillin and Mn2+-amoxicillin systems in NaCl aqueous solution is reported. The potentiometric measurements were carried out under different conditions of temperature (15 ≤ t/°C ≤ 37). The obtained speciation pattern includes two species for both the investigated systems. More in detail, for system containing ampicillin MLH and ML species, for that containing amoxicillin, MLH2 and MLH ones. The spectrophotometric findings have fully confirmed the results obtained by potentiometry for both the systems, in terms of speciation models as well as the stability constants of the formed species. Enthalpy change values were calculated via the dependence of formation constants of the species on temperature. The sequestering ability of ampicillin and amoxicillin towards Mn2+ was also evaluated under different conditions of pH and temperature via pL0.5 empirical parameter (i.e., cologarithm of the ligand concentration required to sequester 50% of the metal ion present in traces).

Stability constants of metal ion complexes formed with N3-deprotonated uridine in aqueous solution

2003 ◽  
Vol 6 (1) ◽  
pp. 90-93 ◽  
Author(s):  
Bernd Knobloch ◽  
Carla P Da Costa ◽  
Wolfgang Linert ◽  
Helmut Sigel
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Metal Ion ◽  
Metal Ion Complexes

Cucurbit[7]uril host-guest complexes with cationic bis(4,5-dihydro-1H-imidazol-2-yl) guests in aqueous solution

2006 ◽  
Vol 84 (6) ◽  
pp. 905-914 ◽  
Author(s):  
D Saroja N Hettiarachchi ◽  
Donal H Macartney
Keyword(s):  
Mass Spectrometry ◽  
Aqueous Solution ◽  
Nmr Spectroscopy ◽  
Stability Constants ◽  
Electrospray Mass Spectrometry ◽  
Hydrophobic Core ◽  
Guest Complex ◽  
H Nmr ◽  
Host Guest Complex ◽  
Proton Resonances

The host–guest interactions between cucurbit[7]uril and a series of novel cationic bis(4,5-dihydro-1H-imidazol-2-yl)arene and 1-(4,5-dihydro-1H-imidazol-2-yl)- and 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)-adamantane guests have been investigated in aqueous solution using UV–vis and NMR spectroscopy, and electrospray mass spectrometry. With the exception of the 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)adamantane (which binds externally to the CB[7]), these guests form very stable inclusion complexes with slow exchange on the 1H NMR timescale. The direction and magnitude of the complexation-induced shifts (CIS) in the proton resonances of the guests are indicative of the residence of the hydrophobic core of the guest within the CB[7] cavity and the charged 4,5-dihydro-1H-imidazol-2-yl units outside the cavity adjacent to the carbonyl-lined portals of the host. The CIS values and the inclusion stability constants have been correlated with the nature of the guest core and with the distance between the charges on the terminal 4,5-dihydro-1H-imidazol-2-yl rings.Key words: cucurbit[7]uril, host–guest complex, dihydroimidazolyl, inclusion stability constants.

Solution properties of metal ion complexes formed with the antiviral and cytostatic nucleotide analogue 9-[2-(phosphonomethoxy)ethyl]-2-amino-6-dimethylaminopurine (PME2A6DMAP)

2014 ◽  
Vol 92 (8) ◽  
pp. 771-780 ◽  
Author(s):  
Raquel B. Gómez-Coca ◽  
Astrid Sigel ◽  
Bert P. Operschall ◽  
Antonín Holý ◽  
Helmut Sigel
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Metal Ion ◽  
Present System ◽  
Therapeutic Effects ◽  
Solution Properties ◽  
Acidity Constants ◽  
Nucleotide Analogue ◽  
Ether Oxygen ◽  
The Stability

The acidity constants of protonated 9-[2-(phosphonomethoxy)ethyl]-2-amino-6-dimethylaminopurine (H3(PME2A6DMAP)+) are considered, and the stability constants of the M(H;PME2A6DMAP)+ and M(PME2A6DMAP) complexes (M2+ = Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, or Cd2+) were measured by potentiometric pH titrations in aqueous solution (25 °C; I = 0.1 mol/L, NaNO3). In the M(H;PME2A6DMAP)+ species, H+ and M2+ (mainly outersphere) are at the phosphonate group; this is relevant for phosphoryl-diester bridges in nucleic acids because, in the present system, there is no indication for a M2+–purine binding. This contrasts, for example, with the complexes formed by 9-[2-(phosphonomethoxy)ethyl]adenine, M(H;PMEA)+, where M2+ is mainly situated at the adenine residue. Application of log [Formula: see text] vs. [Formula: see text] plots for simple phosph(on)ate ligands, R–PO32− (R being a residue that does not affect M2+ binding), proves that all M(PME2A6DMAP) complexes have larger stabilities than what would be expected for a M2+–phosphonate coordination. Comparisons with M(PME–R) complexes, where R is a noncoordinating residue of the (phosphonomethoxy)ethane chain, allow one to conclude that the increased stability is due to the formation of five-membered chelates involving the ether–oxygen of the –CH2–O–CH2–PO32− residue: the percentages of formation of these M(PME2A6DMAP)cl/O chelates, which occur in intramolecular equilibria, vary between 20% (Sr2+, Ba2+) and 50% (Zn2+, Cd2+), up to a maximum of 67% (Cu2+). Any M2+ interaction with N3 or N7 of the purine moiety, as in the parent M(PMEA) complexes, is suppressed by the (C2)NH2 and (C6)N(CH3)2 substituents. This observation, together with the previously determined stacking properties, offers an explanation why PME2A6DMAP2– has remarkable therapeutic effects.

The removal of Cu (II), Cd (II), Ni (II) and Pb (II) from dilute aqueous solution by a poly(acrylic acid) flocculant and its cross-linked analogue

2002 ◽  
Vol 2 (2) ◽  
pp. 27-34 ◽  
Author(s):  
C. Morlay ◽  
Y. Mouginot ◽  
M. Cromer ◽  
O. Vittori
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Metal Ion ◽  
Differential Pulse ◽  
Differential Pulse Polarography ◽  
Conditional Stability ◽  
Complex Species ◽  
Complexing Capacity ◽  
Dilute Aqueous Solution ◽  
Acrylic Acids

The possible removal of copper (II), cadmium (II), nickel (II) and lead (II) from dilute aqueous solution by complexation with poly(acrylic acids) was investigated. The binding properties of two hydrosoluble poly(acrylic acids) of high molecular weight (which make them representative of synthetic flocculants used in the water treatment field; Mw = 2.5 × 105 and 3 × 106 g mol-1) and of an insoluble cross-linked analogue were examined. Potentiometric titrations were carried out, first, to determine the acid-base properties of both polymers and, secondly, to determine the stability constants of the MA and MA2 complex species formed. Metal complexation was also studied using differential pulse polarography. The complexing capacity of each polyacid for the metal ions under study was determined at pH 6.0, 5.0 and 4.0 and the ionic strength was 0.1 or 1.0 mol l-1. The conditional stability constants were estimated assuming that only 1:1 complex species were formed. The results obtained by both methods agree and are complementary. It appeared that stability constants increased in the following order, depending on the metal ion : Ni (II) << Cd (II) < Cu (II) < Pb (II). The hydrosoluble polyacid was able to fix up to 6.3 mmol Pb (II)/g while the insoluble cross-linked analogue was able to fix up to 4.8 mmol Pb (II)/g.

scholarly journals Streptomycin Hydrazone Derivatives: Synthesis and Molecular Recognition in Aqueous Solution

2014 ◽  
Vol 9 (10) ◽  
pp. 1934578X1400901
Author(s):  
Juan P. Fuentes-Martínez ◽  
Diana Gutiérrez-Rodríguez ◽  
Edgar Rogel García ◽  
Karla I. Rivera-Márquez ◽  
Felipe Medrano ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Aqueous Solution ◽  
Adenine Nucleotides ◽  
Antibiotic Activity ◽  
Dominant Factor ◽  
H Nmr ◽  
Derivatives Of ◽  
Multiple Interactions ◽  
Nmr Titrations ◽  
C Nmr

Five hydrazone derivatives of streptomycin were synthetized (D0h, D1ph, D2bt, D3dctf, D4ag) and characterized by IR, 1H and 13C NMR spectroscopy, mass spectrometry and elemental analysis. Protonation constants were determined by potentiometry for all derivatives. D1ph and D2bt derivatives were investigated as receptors of dicarboxylates and adenine nucleotides in aqueous solution by potentiometric and 1H NMR titrations. D1ph and D2bt derivatives have the highest affinity with AMP and ATP, respectively, which shows that electrostatic forces are not always the dominant factor in binding of streptomycin derivatives with nucleotides, but the conformational fit between them. Calculated structures at the DFT level of the D1ph derivative bonded with either AMP or ADP showed that the complexes are stabilized by the formation of multiple interactions with the receptors. The antibiotic activity of the derivatives was explored and compared with native streptomycin.

Complexing behavior of rutin and quercetin

1991 ◽  
Vol 69 (12) ◽  
pp. 1994-2001 ◽  
Author(s):  
Graciela M. Escandar ◽  
Luis F. Sala
Keyword(s):  
Aqueous Solution ◽  
Transition Metal ◽  
Stability Constant ◽  
Key Words ◽  
Stability Constants ◽  
Metal Ion ◽  
Spectrophotometric Methods ◽  
Equilibrium Reactions ◽  
Rutin Aglycone ◽  
Rutin And Quercetin

The equilibrium reactions between rutin, 3-[6-O-(6-deoxy-α-L-mannopyranosyl)-(β-D-glucopyranosyl)oxy]-2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4H-1-benzopyran-4-one, and quercetin (rutin aglycone) with iron(III), copper(II), cobalt(II), and nickel(II) have been studied by potentiometric and spectrophotometric methods in aqueous solution. All measurements were carried out at t = 20 °C and μ = 0.10 M, and the corresponding stability constants were calculated by applying computational methods. The interactions between the proposed cations with both biological ligands and other related ones are compared, with simultaneous postulation of the probable structures. Key words: chelate stability constants of rutin, chelate stability constants of quercetin, transition metal ion interaction with flavonoids, stability constant determinations, potentiometric and spectrophotometric studies.

scholarly journals Stability Constants of Metal Ion - Hydroxylamine Complexes in Aqueous Solution.

1963 ◽  
Vol 17 ◽  
pp. 2674-2680 ◽  
Author(s):  
I. Szilárd ◽  
Einar Jacobsen ◽  
Eeva-Liisa Syväoja ◽  
Armi Alivaara ◽  
M. Trætteberg
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Metal Ion
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