Copper complexation by isatin β-thiosemicarbazones in aqueous solution

1981 ◽  
Vol 34 (12) ◽  
pp. 2549 ◽  
Author(s):  
H Stunzi
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Antiviral Drug ◽  
Copper Electrode ◽  
Water Soluble ◽  
Conditional Stability ◽  
Cupric Ion ◽  
Copper Complexation ◽  
The Stability

The reactions in aqueous solution between cupric ion and water-soluble derivatives of the antiviral drug methisazone (1-methylisatin β-thiosemicarbazone, mibt) have been investigated. Alkalimetric titrations and n.m.r. experiments showed that 5-sulfonatoisatin β-thiosemicarbazone, sibt (3), its 1-methyl derivative, msibt (4), and also p-sulfonatobenzaldehyde thiosemicarbazone, sbat (5), reduce cupric ion and form copper(I) complexes. Stability constants were obtained from measurements of pH and pCu+ on solutions of copper(II) nitrate and excess ligand (I = 0.15 M KNO3, at 37�). The pCu+ values were obtained with an ORION solid state copper electrode. At pH 6-7.5 and moderate excess of ligand, polymeric complexes with an approximate 1 : 1 copper(1)-to-ligand ratio are formed: CunLn or CunLn+,H with n > 6. Monomeric complexes CuL23- predominate at higher pH and in the presence of a more than twentyfold excess of ligand. The stability constants log β2 are 17.9 for sibt, 18.5 for msibt and 19.8 for sbat. At physiological pH (7.4), the order of stability is msibt > sibt & sbat, with conditional stability constants log β2 = 16.2, 15.7 and 13.4, respectively. Comparison with penicillamine shows that some in vivo complexation of copper(I) by methisazone may be possible. On the other hand, a histidinato-copper(II) complex is formed in the presence of histidine.

Can chelation be important in the antiviral activity of isatin β-thiosemicarbazones?

1982 ◽  
Vol 35 (6) ◽  
pp. 1145 ◽  
Author(s):  
H Stunzi
Keyword(s):  
Stability Constants ◽  
Metal Ion ◽  
Copper Ions ◽  
Conditional Stability ◽  
Biologically Relevant ◽  
Cupric Ion ◽  
The Stability ◽  
Conditional Stability Constants ◽  
Metal Ion Chelation

The stability constants of 5-sulfonatoisatin β-thiosemicarbazone (β-thiosemicarbazonoisatin-5- sulfonate) [sibt,(3)] with Zn2+ and Fe2+ have been determined from slow pH titrations (I 0.15M KNO3, 37�). At pH 7.4, the conditional stability constants for the sibt complexes are logK1' 4.5 (Zn2+), 3.1 (Fe2+) and log β2' 8.9 (Zn2+), 6.5 (Fe2+). The mixed ligand complexes Zn(sibt)L (L = histidine or glycine) have conditional stability constants log β1110' 8.8 and 7.0, respectively, at pH 7.4. Copper(I) complexes of sibt and bishistidinato-copper(II) coexist in mixtures of Cu2+, sibt and histidine. [In solutions of copper ions, sibt (complexes Cu+) and histidine (chelates Cu2+), the response of the Orion cupric-ion-selective electrode is not stoichiometric.] Also studied was 1-methyl-5-sulfonatoisatin β-thiosemicarbazone [msibt,(4)] which behaves like sibt. 5-Sulfonatoisatin β-semicarbazone and p-sulfonatobenzaldehyde thiosemicarbazone (p-thiosemicarbazonomethyl- benzenesulfonate) are weak ligands. Comparison of the stability constants with those of complexes of biologically relevant chelating agents showed that isatin β-thiosemicarbazones are not expected to form stable complexes with zinc and iron in vivo. Bidentate thiosemicarbazones, such as benzaldehyde thiosemicarbazones, form even weaker complexes. Both classes of thiosernicarbazones have a similar activity against vaccinia virus; this activity seems not to depend on metal ion chelation.

The Extraction of Anionic Beryllium Complexes by Tri-iso-octylamine

1962 ◽  
Vol 15 (3) ◽  
pp. 457 ◽  
Author(s):  
HJ de Bruin ◽  
D Kairaitis ◽  
RB Temple
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Complexing Agents ◽  
Conditional Stability ◽  
Tertiary Amines ◽  
Ph Titration ◽  
Anionic Complexes ◽  
The Stability ◽  
Conditional Stability Constants ◽  
Beryllium Complexes

The extraction of beryllium from aqueous solution by long-chain tertiary amines has been observed in the presence of ligands giving rise to anionic complexes. The nature of the oxalate complex extracted by solutions of tri-iso-octylamine in chloroform has been studied in detail and the species formed in the organic phase were shown to have the composition Be(C2O4)2.{NH(i-C8H15)3}2. The complexes formed in aqueous solution between beryllium and several anionic complexing agents have been examined by the method of pH-titration. Conditional stability constants have been obtained for the complexes formed with oxalic, malonic, maleic, succinic, phthalic, and salicylic acids. Differences in their extractabilities can be explained semiquantitatively with the help of the stability constants and the acid association constants of the complexing agents.

Studies on the Coordination Reaction of VO2+ and Tannic Acid in the Tannin Extract Desulfurization

2012 ◽  
Vol 239-240 ◽  
pp. 1573-1576
Author(s):  
Zhu Qing Gao ◽  
Xiao Dong Cai ◽  
Kai Cheng Ling
Keyword(s):  
Stability Constants ◽  
Tannic Acid ◽  
Ph Value ◽  
Protonation Constants ◽  
Conditional Stability ◽  
Tannin Extract ◽  
Acid Effect ◽  
Different Temperatures ◽  
The Stability ◽  
Apparent Stability

At different temperatures, the protonation constants of tannic acid and the complex apparent stability constants between tannic acid and VO2+ were determined by using pH potentimetric method. The results showed that the protonation constants and the complex apparent stability constants slightly decreased with the raising temperature. In accordance with the pH value in the tannin extract technology, the conditional stability constants of the complex were calculated on the basis of the acid effect of tannic acid and the hydrolysis effect of VO2+. It was found that pH greatly affected the stability constants of the complex , so pH must be strictly controlled in the tannin extract technology.

scholarly journals Copper(II)-complexation by non enzymatically glycated peptides

2004 ◽  
Vol 22 (SI - Chem. Reactions in Foods V) ◽  
pp. S106-S108
Author(s):  
S. T Seifert ◽  
R. Krause ◽  
K. Gloe ◽  
T. Henle
Keyword(s):  
Aqueous Solution ◽  
Metal Ions ◽  
Stability Constants ◽  
Maillard Reaction ◽  
Metal Binding ◽  
Maillard Reaction Products ◽  
Reaction Products ◽  
Nonenzymatic Glycation ◽  
The Stability

The purpose of our work was to examine the metal binding abilities of selected peptide bound Maillard reaction products (MRPs). The N<sup>α</sup>-hippuryl-protected MRPs N<sup>ε</sup>-fructoselysine and N<sup>ε</sup>-carboxymethyllysine were synthesised and measurement of stability constants for complexes formed with the physiologically important metal ions copper(II) and zinc(II) was carried out in aqueous solution (T = 298.1 K; I = 0.1M KNO<sub>3</sub>) using pH-potentiometry. The stability constants of N<sup>ε</sup>-fructoselysine and N<sup>ε</sup>-carboxymethyllysine with Cu(II) proved that new coordination centres are formed by the nonenzymatic glycation of proteins. With zinc(II) no complexation was observed. Physiological consequences are discussed, but further studies are necessary in order to clarify the effects of this phenomenon.

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).

A Novel pH-Sensitive Microsphere Composed of CM-Chitosan and Alginate for Sulforaphane Delivery

2011 ◽  
Vol 687 ◽  
pp. 539-547 ◽  
Author(s):  
Hui Wang ◽  
Hao Liang ◽  
Qi Peng Yuan ◽  
Tian Xin Wang
Keyword(s):  
Sodium Sulfate ◽  
Anticancer Agent ◽  
Ph Sensitive ◽  
Water Soluble ◽  
Ph Values ◽  
Swelling Studies ◽  
The Stability ◽  
Carboxymethylated Chitosan

Sulforaphane (SF) has been proved to be an effective anticancer agent according to its experiments bothin vitroandin vivo. To date, there is few reported method to deliver SF for increasing its bioactivity and stability. In this study, a novel pH-sensitive microsphere composed of water-soluble carboxymethylated chitosan (CMCS) and alginate mixed with sodium sulfate was developed for SF delivery. Swelling studies and release characteristics under different pH values of microspheres were investigated. Then, the release of SF from test microspheres was studied in simulated gastric and segmented intestinal media. It has been found that the SF cumulated release in 5h was increased from 55.89% to 76.73% when the microspheres mixed with sodium sulfate. In addition, the stability of SF embedded in CMCS/alginate microspheres was also significantly improved. Under pH 7.4, free SF had a severe degradation of approximate 100% within 210 min, whereas the change of the SF in microspheres was only a decrease of about 10%. The results suggested that the microspheres of CMCS and alginate could be a suitable pH-sensitive carrier to increase the stability of SF in the segmented intestine.

Sign in / Sign up

Export Citation Format

Share Document