Stability, Structure and Reactivity of Mixed Ligand Complexes in Solution

Sigel, Helmut

doi:10.1016/b978-0-08-023942-2.50009-2

Cited by 35 publications

(3 citation statements)

References 83 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…is displaced to the right in accord with other observations for similar mixed-ligand complexes. 35,36,192,384 The results described for the ligands 48-50 have initiated further studies, namely of the Cu2+ and Ni2+ complexes of 3,7-diazanonanediamide and its diethyl Even heterometal tetranuclear complexes of the type Mn[Cun(L-2H)]3(C104)2 or (N03)2, where M11 = Co2+ or Ni2+, could be isolated, and the general structure 64 'M2* 64 was proposed for these species. 387 For N,N'-bis(2aminoethyl)oxalamide (50) as ligand the Ni2+ complex was obtained, and for N^N-bis(3-aminopropyl)oxalamide the Co2+ and Ni2+ hetero tetranuclear species were prepared.…”

Section: Selected Examples Of Other Amidesmentioning

confidence: 99%

Coordinating properties of the amide bond. Stability and structure of metal ion complexes of peptides and related ligands

Sigel¹,

Martin²

1982

View full text Add to dashboard Cite

Section: Selected Examples Of Other Amidesmentioning

confidence: 99%

Coordinating properties of the amide bond. Stability and structure of metal ion complexes of peptides and related ligands

Sigel¹,

Martin²

1982

View full text Add to dashboard Cite

“…In order to characterize the coordination tendency of the ligand PO 4 3− toward [Ca(cit)] − , the value of Δlog K Ca was calculated, as suggested by H. Sigel [ 16 ]. Δlog K Ca is the difference between the partial formation constant of the mixed complex—

and the partial formation constant of the complementary complex—

…”

Section: Resultsmentioning

confidence: 99%

“…The Δlog K Ca quantifies the stability of the ternary complex, relative to the binary parent complex. The statistically expected value of Δlog K Ca , evaluated by H. Sigel [ 16 ] for the coordination of two different bidentate ligands to a regular octahedral coordination sphere, is −0.38. The value of Δlog K Ca obtained for [Ca(PO 4 )cit] 4− is more strongly negative than that statistically expected.…”

Section: Resultsmentioning

confidence: 99%

Critical Reappraisal of Methods for Measuring Urine Saturation with Calcium Salts

Berto

Marangella²,

Stefano

et al. 2021

Molecules

View full text Add to dashboard Cite

Background: Metabolic and physicochemical evaluation is recommended to manage the condition of patients with nephrolithiasis. The estimation of the saturation state (β values) is often included in the diagnostic work-up, and it is preferably performed through calculations. The free concentrations of constituent ions are estimated by considering the main ionic soluble complexes. It is contended that this approach is liable to an overestimation of β values because some complexes may be overlooked. A recent report found that β values could be significantly lowered upon the addition of new and so far neglected complexes, [Ca(PO4)Cit]4− and [Ca2H2(PO4)2]. The aim of this work was to assess whether these complexes can be relevant to explaining the chemistry of urine. Methods: The Ca–phosphate–citrate aqueous system was investigated by potentiometric titrations. The stability constants of the parent binary complexes [Cacit]− and [CaPO4]−, and the coordination tendency of PO43− toward [Ca(cit)]− to form the ternary complex, were estimated. βCaOx and βCaHPO4 were then calculated on 5 natural urines by chemical models, including or not including the [CaPO4]− and [Ca(PO4)cit]4− species. Results: Species distribution diagrams show that the [Ca(PO4)cit]4− species was only noticeable at pH >8.5 and below 10% of the total calcium. β values estimated on natural urine were slightly lowered by the formation of [CaPO4]− species, whereas [Ca(PO4)cit]4− results were irrelevant. Conclusions: While [CaPO4]− species have an impact on saturation levels at higher pHs, the existence of ternary complex and of the dimer is rejected.

show abstract

Extent of Intramolecular π‐Stacks in Aqueous Solution in Mixed‐Ligand Copper(II) Complexes Formed by Heteroaromatic Amines and Several 2‐Aminopurine Derivatives of the Antivirally Active Nucleotide Analog 9‐[2‐(Phosphonomethoxy)ethyl]adenine (PMEA)

Gómez‐Coca

Blindauer

Sigel

et al. 2012

Chemistry & Biodiversity

View full text Add to dashboard Cite

The acidity constants of twofold protonated, antivirally active, acyclic nucleoside phosphonates (ANPs), H2(PE)±, where PE2−=9‐[2‐(phosphonomethoxy)ethyl]adenine (PMEA2−), 2‐amino‐9‐[2‐(phosphonomethoxy)ethyl]purine (PME2AP2−), 2,6‐diamino‐9‐[2‐(phosphonomethoxy)ethyl]purine (PMEDAP2−), or 2‐amino‐6‐(dimethylamino)‐9‐[2‐(phosphonomethoxy)ethyl]purine (PME(2A6DMAP)2−), as well as the stability constants of the corresponding ternary Cu(Arm)(H;PE)+ and Cu(Arm)(PE) complexes, where Arm=2,2′‐bipyridine (bpy) or 1,10‐phenanthroline (phen), are compared. The constants for the systems containing PE2−=PMEDAP2− and PME(2A6DMAP)2− have been determined now by potentiometric pH titrations in aqueous solution at I=0.1M (NaNO3) and 25°; the corresponding results for the other ANPs were taken from our earlier work. The basicity of the terminal phosphonate group is very similar for all the ANP2− species, whereas the addition of a second amino substituent at the pyrimidine ring of the purine moiety significantly increases the basicity of the N(1) site. Detailed stability‐constant comparisons reveal that, in the monoprotonated ternary Cu(Arm)(H;PE)+ complexes, the proton is at the phosphonate group, that the ether O‐atom of the CH2OCH2P(O)$\rm{{_{2}^{-}}}$(OH) residue participates, next to the P(O)$\rm{{_{2}^{-}}}$(OH) group, to some extent in Cu(Arm)2+ coordination, and that ππ stacking between the aromatic rings of Cu(Arm)2+ and the purine moiety is rather important, especially for the H⋅PMEDAP− and H⋅PME(2A6DMAP)− ligands. There are indications that ternary Cu(Arm)2+‐bridged stacks as well as unbridged (binary) stacks are formed. The ternary Cu(Arm)(PE) complexes are considerably more stable than the corresponding Cu(Arm)(RPO3) species, where RPO$\rm{{_{3}^{2-}}}$ represents a phosph(on)ate ligand with a group R that is unable to participate in any kind of intramolecular interaction within the complexes. The observed stability enhancements are mainly attributed to intramolecular‐stack formation in the Cu(Arm)(PE) complexes and also, to a smaller extent, to the formation of five‐membered chelates involving the ether O‐atom present in the CH2OCH2PO$\rm{{_{3}^{2-}}}$ residue of the PE2− species. The quantitative analysis of the intramolecular equilibria involving three structurally different Cu(Arm)(PE) isomers shows that, e.g., ca. 1.5% of the Cu(phen)(PMEDAP) system exist with Cu(phen)2+ solely coordinated to the phosphonate group, 4.5% as a five‐membered chelate involving the ether O‐atom of the CH2OCH2PO$\rm{{_{3}^{2-}}}$ residue, and 94% with an intramolecular ππ stack between the purine moiety of PMEDAP2− and the aromatic rings of phen. Comparison of the various formation degrees of the species formed reveals that, in the Cu(phen)(PE) complexes, intramolecular‐stack formation is more pronounced than in the Cu(bpy)(PE) species. Within a given Cu(Arm)2+ series the stacking intensity increases in the order PME2AP2−

show abstract

Stability, Structure and Reactivity of Mixed Ligand Complexes in Solution

Cited by 35 publications

References 83 publications

Coordinating properties of the amide bond. Stability and structure of metal ion complexes of peptides and related ligands

Coordinating properties of the amide bond. Stability and structure of metal ion complexes of peptides and related ligands

Critical Reappraisal of Methods for Measuring Urine Saturation with Calcium Salts

Extent of Intramolecular π‐Stacks in Aqueous Solution in Mixed‐Ligand Copper(II) Complexes Formed by Heteroaromatic Amines and Several 2‐Aminopurine Derivatives of the Antivirally Active Nucleotide Analog 9‐[2‐(Phosphonomethoxy)ethyl]adenine (PMEA)

Contact Info

Product

Resources

About