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1979 (1)
1Author    Etelka Farkas, BedaE. Fischer, Rolf Griesser, VolkerM. Rheinberger, Helmut SigelRequires cookie*
 Title    Ternary Complexes in Solution, XXX [1] Increased Stability Through Intramolecular Stacking in Mixed-Ligand Cu 2+ and Zn 2+ Complexes of 2,2' -Bipyridyl and Carboxymethyl Aryl Derivatives  
 Abstract    The stability constants of ternary Cu 2+ and Zn 2+ complexes, each of which contains 2,2'-bipyridyl and a carboxymethyl aryl sulfide, were determined in 50% aqueous dioxane. A comparison of the stability of these ternary complexes with those formed with simple carboxylates demonstrates an enhanced stability of the carboxymethyl aryl sulfide containing mixed ligand complexes. This enhanced stability is not due to a thioether-metal ion interaction, but due to an intramolecular aromatic stacking interaction between the aryl moiety of the carboxymethyl aryl sulfide and 2,2'-bipyridyl. Indeed, by UV difference spectra and by PMR measurements it is possible to show that a binary (metal ion-free) stacked adduct between the aromatic moieties of the two mentioned ligands is formed. Furthermore, by studying the binary and ternary systems of Zn 2+ or Cu 2+ , 2,2'-bipyridyl and hydrocinnamate, i.e. 3-phenylpropionate (-S-of carboxymethyl phenyl sulfide is replaced by -CH2-), it becomes obvious that the thioether moiety is not essential for the observation of an enhanced stability of the ternary complexes. PMR shift studies of 2,2'-bipyridyl/Zn 2+ /carboxymethyl aryl sulfide systems confirm the presence of stacking in the corresponding ternary complexes. Depending on the kind of the ternary metal ion complex the stability enhancement, due to the intramolecular stacking between the aro-matic parts of the coordinated ligands, is between about 0.2 to 0.5 log unit. 
  Reference    Z. Naturforsch. 34b, 208—216 (1979); received September 1 1978 
  Published    1979 
  Keywords    Mixed-Ligand Complexes, Stacking Interactions, 2, 2'-Bipyridyl, 3-Phenylpropionate, Carboxymethyl Aryl Sulfides 
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 TEI-XML for    default:Reihe_B/34/ZNB-1979-34b-0208.pdf 
 Identifier    ZNB-1979-34b-0208 
 Volume    34