Free-energy Relationships in Coordination Chemistry. III. A Comprehensive Index to Complex Stability

Nieboer, Evert; McBryde, W. A. E.

doi:10.1139/v73-379

Cited by 101 publications

(39 citation statements)

References 28 publications

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“…An alternative linear free energy approach to the characterization of ligands is the use of the stability index, Q, and related derived parameters (46). As above, the results were considerably more scattered than for simple ligands but consistently indicated that the aza crowns of this study were more typical of class b behaviors.…”

Section: Interligand Comparisonssupporting

confidence: 51%

Polycarboxylate diaza crown ethers derived from R,R-(+)-tartaric acid: synthesis and complexation of metal ions

Anantanarayan¹,

Fyles²

1990

Can. J. Chem.

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ASHOK ANANTANARAYAN and THOMAS M. FYLES. Can. J. Chem. 68, 1338 (1990.The synthesis and complexation properties of polycarboxylate diaza crown ethers based on R,R-(+)-tartaric acid are described. Cesium carbonate mediated macrocyclization of a bis-tosylamide precursor with a bis-tosylate precursor provided the protected crown ethers. Photochemical deprotection of the tosylamides and hydrolysis of the carboxamides yielded dicarboxylic and tetracarboxylic acid derivatives of 1, lO-diaza-18-crown-6. N-Methylenecarboxylate (N-acetate) derivatives were prepared by N-alkylation with bromoacetic acid. The synthetic and purification procedures developed provide samples of the ligands in a metal-free form. Acidity and stability constants for complexation of alkali metal, alkaline earth, late-and post-transition metal cations were determined by potentiometric titration. The ligands form complexes which show enhancement of stability by charge-charge and chelate interaction with the carboxylates. In comparison with crown ether polycarboxylates these aza crown ethers showed a selectivity for softer metal ions relative to alkali and alkaline earth metal ions. N-Methylenecarboxylate chelate ligands were found to bind almost all types of metal ions, due to a highly co-operative array of charge-charge, chelate and crown ether interactions. Metal ion recognition by synthetic and naturally occurring ligands is a complex process involving a cooperative match of the complementary properties of the host and the guest. A key factor in the design of new ligands with unique complexation behaviors is the choice of ligand donor sites (1). Within a class of ligands, such as the crown ethers or cryptands, clear changes in selectivity of cation binding are provoked by substitution of the oxygen donors of a parent ring system for nitrogen or sulfur donor sites (2). Such substitutions alter the primary character of the donor (Lewis basicity) as well as the geometrical and conformational properties of the ligand (3). Thus in a system involving highly cooperative binding interactions, donor atom substitution can profoundly influence binding selectivity.Our interest in ligand design has centered on crown ethers derived from R,R-(+)-tartaric acid: the di-, tetra-, and hexaacids illustrated at the top of Fig. 1 (4-6). The tartarate derived units impart rigidity to the ligands, leading to well defined conformations, and the carboxylates, when ionized, provide a strong electrostatic field which greatly enhances complex stability for alkali metal and alkaline earth cations. Despite the favorable Coulombic interactions, binding of heavy metal cations occurs only to a limited extent due to a mismatch of the hard oxygen donor set and the softer guest cations (6). An obvious ligand modification which might lead to stabilized crown ether type complexes of heavier cations would be the substitution of some of the donor atoms for N or S. We have previously reported dithia crown ethers bearing four carboxylates (7); the purpose of this report is to describe th...

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Section: Interligand Comparisonssupporting

confidence: 51%

Polycarboxylate diaza crown ethers derived from R,R-(+)-tartaric acid: synthesis and complexation of metal ions

Anantanarayan¹,

Fyles²

1990

Can. J. Chem.

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“…The high affinity of Enteromorpha prolifera for Cu(II) cations could result from the ionic characteristics of Cu(II). Nieboer and McBryde et al [20] proposed a covalent index, which was calculated using the equation: …”

Section: Biosorption In Multi-metal Systemsmentioning

confidence: 99%

Effects of anions on the biosorption of microelement cations by macroalga Enteromorpha prolifera in single- and multi-metal systems

Michalak

Chojnacka

2012

Chin. Sci. Bull.

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The results of research on the effects of anions on the biosorption of microelement cations by the edible marine macroalga Enteromorpha prolifera in single-and multi-metal systems are discussed in this paper. It was shown that the maximum biosorption capacity (q max ) in a single-metal system of Co (II) The biosorption of metal ions by algae has been widely reported in the literature. However, the majority of the published work describes single-metal biosorption systems. Very little information is available on multi-metal biosorption systems such as binary [1][2][3][4][5], ternary [1,[4][5][6], and quaternary systems [7]. There is a necessity to perform experiments on such systems because they better reflect real effluents from industrial operations. Another issue, which is often neglected in the literature, is the investigation of the effects of anions on biosorption processes. This aspect should also be taken into consideration because the presence of anions in aqueous solutions could affect metal cation biosorption [8].In the literature, two aspects of the effects of anions on biosorption processes are considered: the effects of anions on the maximum biosorption capacity in single-metal systems [9], and the effects of anion concentration on the biosorption of several metal ions in multi-metal systems [8,10,11]. It is important to emphasize that the influence of the anion on the biosorption capacity could differ depending on the biomass used and the biosorbed metal ions. The anions NO 3 -and SO 4 2-did not significantly influence the removal efficiency of the fungus Aspergillus niger for Cr(VI), Co(II), Ni(II), and Zn(II) ions, whereas the presence of Cl -anions significantly decreased the efficiency of metal ion biosorption in multi-metal systems [10]. In the case of another fungus, namely Rhizopus arrhizus, the degree of inhibition of the biosorption of La(III), Cd(II), Pb(II), and Ag(I) cations generally followed the order EDTA > SO 4 2-> Cl -> PO 4 3-> glutamate > CO 3 2- [12]. During biosorption of Co(II) cations by the brown macroalga Ascophylum nodosum, the presence of SO 4 2-and PO 4 3-anions did not result in any change in biosorption, in contrast to NO 3 -anions, which were the strongest inhibitor [13]. The opposite situation was observed in the case of biosorption of Zn(II) cations by the cyanobacterium Oscillatoria anguistissim, for which the inhibitory order of the anions was as follows: SO 4 2-> Cl -> NO 3 -(i.e., SO 4 2-anions were the strongest inhibitor) [11].

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“…Table 3 shows that the affinity increases in the following order Cd(II) < Cu(II) < Pb(II) for all biosorbents. The covalent index (product of the electronegativity square by the sum of the ionic radius and 0.85, which is an appropriate constant assumed to reflect the radius of O and N donor atoms) also increases in the order: Cd(II) (5.20) < Cu(II) (6.32) < Pb(II) (6.61) [45]. In general, the greater the covalent index of a metal ion, the greater its Class B character, and consequently its potential to form covalent bonds with biological ligands.…”

Section: Effect Of Phmentioning

confidence: 99%

Cadmium uptake by algal biomass in batch and continuous (CSTR and packed bed column) adsorbers

Vilar¹,

Santos²,

Martins³

et al. 2008

Biochemical Engineering Journal

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a b s t r a c tIn this work, the properties of marine algae Gelidium, algal waste from agar extraction industry and a composite material were investigated for cadmium(II) biosorption. Equilibrium experiments were performed at three pH values (4, 5.3 and 6.5). Equilibrium data were well described by the Langmuir and Langmuir-Freundlich isotherms. Two models predicting the pH influence in the cadmium biosorption (discrete and continuous models) have been developed in order to better describe the equilibrium. The continuous model also considers a heterogeneous distribution of carboxylic groups, determined by potentiometric titration. The results of batch kinetic experiments performed at different pH values were well fitted by two mass transfer models and the homogeneous diffusion coefficients for the cadmium ions inside the biosorbent were obtained. Continuous stirred tank reactor (CSTR) and packed bed column configurations were also examined for the biosorption of cadmium ions. A strong acid (0.1 M HNO 3 ) was used as eluant to regenerate the biosorbents in the column. Several mass transfer models were applied with success to describe the biosorption process in batch mode, CSTR and fixed bed column.

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Free-energy Relationships in Coordination Chemistry. III. A Comprehensive Index to Complex Stability

Cited by 101 publications

References 28 publications

Polycarboxylate diaza crown ethers derived from R,R-(+)-tartaric acid: synthesis and complexation of metal ions

Polycarboxylate diaza crown ethers derived from R,R-(+)-tartaric acid: synthesis and complexation of metal ions

Effects of anions on the biosorption of microelement cations by macroalga Enteromorpha prolifera in single- and multi-metal systems

Cadmium uptake by algal biomass in batch and continuous (CSTR and packed bed column) adsorbers

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