Aluminum(III)-Malonate Equilibria: a Potentiometric Study

1993 ◽  
Vol 46 (5) ◽  
pp. 721 ◽  
Author(s):  
HKJ Powell ◽  
RM Town
Keyword(s):  
Aqueous Solution ◽  
Potentiometric Titration ◽  
Malonic Acid ◽  
Ion Pairing ◽  
Protonation Constants ◽  
Potentiometric Study ◽  
Binary Complexes ◽  
Ph Range ◽  
A Minor

The aluminium(III)-malonic acid (H2L) equilibria have been studied by potentiometric titration in aqueous solution at 25°C (I = 0.10 M KCl ). Data were consistent with the formation of simple binary complexes AlL + (log K1 = 6.711), AlL2- (log K2 = 4.815) and AlL33- (logβ3 = 14.104) in the pH range 2.2-5.5. There was also evidence for a minor species AlL2(OH)2- at pH > 5.8 for solutions with [Al3+]:[LH2] < 3.0 (log KD= -6.68). The protonation constants determined for malonic acid were log K1 = 5.43 and log K2 = 2.60 (corrected for K+ ion pairing).

Aluminium(III) and Iron(III) 1,2-Diphenolato Complexes: a Potentiometric Study

1985 ◽  
Vol 38 (5) ◽  
pp. 659 ◽  
Author(s):  
JA Kennedy ◽  
HKJ Powell
Keyword(s):  
Aqueous Solution ◽  
Potentiometric Titration ◽  
Protocatechuic Acid ◽  
Acid System ◽  
Experimental Conditions ◽  
Potentiometric Study ◽  
Hydroxo Complexes ◽  
Equilibrium Reactions ◽  
Ternary Metal ◽  
Metal Ligand

The equilibrium reactions between aluminium(III) and the phenols catechol (LH2), protocatechuic acid (LH3) and catechin (LH4), and between iron(III) and protocatechuic acid have been studied by potentiometric titration in aqueous solution, I 0.10M ( KCl ), 25°C. Stability constants are reported for the mononuclear diphenolato complexes AlLHn-2, Al(LHn-2)2and Al(LHn-2)3, and the hydroxo complexes Al(OH)LHn-2 and Al(OH)(LHn-2)2, n = 2 ( catechol ) or 4 ( catechin ). For protocatechuic acid, the carboxylate -coordinated species lLH22+ and the species AlLH + (carboxyl- protonated ) are also postulated. Analogous species were characterized for the iron(III)- protocatechuic acid system. Stoichiometric end-points were obtained only if an excess of ligand was used (L/M > 4). Monomeric and polymeric aluminium- hydroxo species and ternary metal- ligand - hydroxo species were found to be unimportant under the experimental conditions employed.

β-Cyclodextrin Inclusion of Adamantane Derivatives in Solution

1990 ◽  
Vol 43 (12) ◽  
pp. 2119 ◽  
Author(s):  
R Palepu ◽  
VC Reinsborough
Keyword(s):  
Aqueous Solution ◽  
Binding Constants ◽  
Minor Role ◽  
Adamantane Derivatives ◽  
Substituent Group ◽  
Cyclodextrin Inclusion ◽  
Cyclodextrin Cavity ◽  
Ph Range ◽  
A Minor

The binding constants for β- cyclodextrin inclusion in aqueous solution of a few simple adamantane salts have been determined by a conductimetric technique at 25°C over the pH range 4-10. Binding was largely dictated by the closeness of fit of the adamantyl moiety within the β- cyclodextrin cavity with the charge on the substituent group playing a minor role. The strongest binding occurred when the charge was neutralized by protonation or deprotonation.

Cyclodextrin and Termethylated Cyclodextrin Complexation of Aromatic Carboxylic Acids and Their Conjugate Bases in Aqueous Solution: the Effect of Size, Hydrophobicity and Charge

1995 ◽  
Vol 48 (6) ◽  
pp. 1125 ◽  
Author(s):  
K Hendrickson ◽  
CJ Easton ◽  
SF Lincoln
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acids ◽  
Potentiometric Titration ◽  
Complexation Constants ◽  
Cyclodextrin Complexes ◽  
Aromatic Carboxylic Acids ◽  
Factors Influencing ◽  
Cyclodextrin Complexation ◽  
Binary Complexes ◽  
Conjugate Bases

For α- cyclodextrin ( αCD ), the complexation constants (K) for the formation of binary host-guest complexes ( HA.αCD ) are 750�60, 1070�60, 27�3 and 17�4 dm3 mol-1 when the guests (HA) are benzoic, 4-methylbenzoic and (R)- and (S)-2-phenylpropanoic acids, respectively, as determined by potentiometric titration in aqueous solution at 298.2 K and I = 0.10 mol dm-3 ( KCl ). For the analogous hexakis (2,3,6-tri-O-methyl)-α- cyclodextrin complexes ( HA.TMαCD ), K = 1580�150, 2890�130, 220�10 and 207�8 dm3 mol-1, and for the heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin complexes ( HA.TMαCD ), K = 200�20, 340�30, 129�5 and 170�10 dm3 mol-1. The binary complexes formed by the corresponding carboxylates (A-) are much less stable. Ternary host-guest α- cyclodextrin complexes (HA.αCD2) are also formed. These data, together with literature data for β- cyclodextrin, are discussed in terms of the factors influencing complexation.

Aluminum(III)-Isocitrate Solution Chemistry. A Potentiometric Study

1995 ◽  
Vol 48 (5) ◽  
pp. 1039
Author(s):  
KJ Powell ◽  
RM Town
Keyword(s):  
Potentiometric Titration ◽  
Thermodynamic Stability ◽  
Protonation Constants ◽  
Solution Chemistry ◽  
Potentiometric Study ◽  
Equilibrium Reactions

The equilibrium reactions of isocitrate with protons and Al3+ have been studied by potentiometric titration in aqueous 0.10 M KCl at 25°C. The protonation constants, corrected for K+-isocitrate complexing , were logβ0,1,1 = 5.838, logβ0,2,1 = 10.126 and logβ0,3,1 = 13.219. The stabilities and stoichiometries of the complexes, AlpHqLr, were defined by the constants logβ1,1,1 = 9.55(05), logβ1,0,1 = 6.90(02), logβ1,-1,1 = 3.06(04) and logβ2,-3,2 = 4.08(04) or logβ3,-4,3 = 10.36(06). Compared with the Al3+-citrate system, complexes are of lower thermodynamic stability, but equilibrate more rapidly.

scholarly journals The Unusual Role of Pro in Cu(II) Binding by His2-Cyclopentapeptide

2021 ◽  
Vol 22 (12) ◽  
pp. 6628
Author(s):  
Aleksandra Pieniężna ◽  
Aleksandra Kotynia ◽  
Justyna Brasuń
Keyword(s):  
Amino Acid ◽  
Potentiometric Titration ◽  
Amino Acid Residue ◽  
Strong Impact ◽  
Mononuclear Complexes ◽  
Study Results ◽  
Metal Ratio ◽  
Ph Range ◽  
L1 And L2

In this paper, we present findings from studying the interaction of copper(II) ions with the His2-cyclopentapeptide and the role of proline used for the purpose of potentiometric titration and UV-Vis, CD and EPR spectroscopic measurements. Experiments of two homodetic peptides differing by one amino acid residue were conducted for a ligand to metal ratio of 1:1 in the pH range 2.5–11.0. The presented studies reveal that peptides form only mononuclear complexes, and the CuH2L complex appears in the system first (for both L1 and L2). Study results show that the presence of Pro influences the structure of formed complexes and their stabilities and has a strong impact on the efficiency of copper(II) coordination.

Schiff base equilibria. II. Beryllium complexes of N-n-butylsalicylideneimine and the hydrolysis of the Be2+ ion

1965 ◽  
Vol 18 (5) ◽  
pp. 651 ◽  
Author(s):  
RW Green ◽  
PW Alexander
Keyword(s):  
Aqueous Solution ◽  
Schiff Base ◽  
Complex Formation ◽  
Distribution Coefficient ◽  
Dilute Aqueous Solution ◽  
The Stability ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Beryllium Complexes ◽  
Equilibria In Aqueous Solution

The Schiff base, N-n-butylsalicylideneimine, extracts more than 99.8% beryllium into toluene from dilute aqueous solution. The distribution of beryllium has been studied in the pH range 5-13 and is discussed in terms of the several complex equilibria in aqueous solution. The stability constants of the complexes formed between beryllium and the Schiff base are log β1 11.1 and log β2 20.4, and the distribution coefficient of the bis complex is 550. Over most of the pH range, hydrolysis of the Be2+ ion competes with complex formation and provides a means of measuring the hydrolysis constants. They are for the reactions: Be(H2O)42+ ↔ 2H+ + Be(H2O)2(OH)2, log*β2 - 13.65; Be(H2O)42+ ↔ 3H+ + Be(H2O)(OH)3-, log*β3 -24.11.

Hydration and contact ion pairing of Ca2+ with Cl− in supercritical aqueous solution

2006 ◽  
Vol 125 (9) ◽  
pp. 094507 ◽  
Author(s):  
John L. Fulton ◽  
Yongsheng Chen ◽  
Steve M. Heald ◽  
Mahalingam Balasubramanian
Keyword(s):  
Aqueous Solution ◽  
Ion Pairing ◽  
Supercritical Aqueous Solution

scholarly journals Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

2014 ◽  
Vol 13 (1) ◽  
Author(s):  
Dariusz Wyrzykowski ◽  
Joanna Pranczk ◽  
Dagmara Jacewicz ◽  
Aleksandra Tesmar ◽  
Bogusław Pilarski ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Hydroxo Complexes ◽  
Binary Complexes ◽  
Vis Spectroscopy ◽  
Potentiometric Titration Method ◽  
The Stability ◽  
Ph Range

AbstractA potentiometric titration method (PT) and a stopped-flow kinetic technique monitored by a UV−Vis spectroscopy have been used to characterize the stability of series of Co(II)- and Ni(II)-thiodiacetato complexes, M(TDA), in the presence of 1,10-phenanthroline (phen) or 2,2’-bipyridine (bipy) in aqueous solutions. The stability constants of the binary (1:1), ternary (1:1:1) as well as the resulting hydroxo complexes were evaluated and compared to the corresponding oxydiacetate complexes. Based on the species distribution as a function of pH the relative predominance of the species in the system over a pH range was discussed. Furthermore, the kinetic measurements of the substitution reactions of the aqua ligands to phen or bipy in the coordination sphere of the binary complexes M(TDA) were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (0.2–0.5 mM). The kinetic stability of the M(TDA) complexes was discussed in relation to the experimental conditions and the kind of the auxiliary ligands (phen/bipy). Moreover, the influence of the type of primary ligand (thiodiacetate/oxydiacetate) on the substitution rate of the auxiliary ligands was also compared.

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