ULTRAVIOLET SPECTRA OF [ILL] COMPOUNDS<sup>1</sup>

Linnell, Robert H.; Kaczmarczyk, Alexander

doi:10.1021/j100825a025

Cited by 100 publications

(45 citation statements)

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“…Absorbance spectra were recorded with a Varian Techtron spectrophotometer (pK#2(phen) = -1.6). 25 The acidity constant KHtphen) I ? (Model 635) connected to a Honeywell recorder (Model 196).…”

Section: Determination Of Equilibrium Constants Bymentioning

confidence: 99%

Ternary complexes in solution. 28. Enhanced stability of ternary metal ion/adenosine 5'-triphosphate complexes. Cooperative effects caused by stacking interactions in complexes containing adenosine triphosphate, phenanthroline, and magnesium, calcium, or zinc ions

Mitchell¹,

Sigel²

1978

J. Am. Chem. Soc.

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The stability constants of the mixed-ligand complexes of ATP, 1, IO-phenanthroline (phen), and Mg2+, Ca2+, Mn2+, Cu2+, or Zn2+ (M2+) have been determined by potentiometric titration. Changes in the stabilities are quantified by A log K M = log K$$$(AT~) -log KE(ATP), corresponding to the equilibrium M(ATP)2-+ M(phen)2+ M(phen)(ATP)2-+ M2+.For the Ca2+, Mg2+, Zn2+, Mn2+, and Cu2+ systems A log K M is 0.6,0.4, 0.22, 0.12, and 0.05, respectively. The stability enhancement in the Ca2+ and Mg2+ systems has also been determined more precisely by ultraviolet-difference spectroscopy, A log K M = 0.53 and 0.55, respectively. All these ternary complexes are much more stable than expected on statistical grounds; in fact, the observation ofposiriue values for A log K M means that ATP4-binds more tightly to M(phen)2+ than to M2+. The formation of stacked adducts between phen and adenosine or ATP has been observed by difference spectroscopy and by ' H N M R and the stability of these adducts has been determined. 'H N M R of the phen/ATP4-/Mg2+ and phen/ATP4-/Zn2+ systems confirms the presence of stacking in the ternary complexes. This stacking causes the increased stability of the ternary Mg2+ and Ca2+ complexes.As many enzymes require activation by metal ions' and as this often involves a ternary enzyme/substrate/metal ion ~o m p l e x ,~ ternary metal ion complexes have received considerable attention in recent years.5 Ternary Cu2+ complexes are the best studied group,6 and relatively little work has been done on ions of other transition metal^,^-^ the lanthanides,I0 zinc,8,11 cadmium,I2 mercury,13 a l~m i n i u m ,~~, '~ and lead.15 Although ternary Ca2+ complexes have been reported,I5.l6 the group I and I1 metal ions have largely been ignored. These metal ions play major biochemical role^,^^,'^ for example, Na+ and K+ in nerves," Ca2+ in muscles, and Mg2+ in energy transfer and storage as high-energy phosphates3 Yet despite the requirement3 of Mg2+ by most enzymes which use ATPI9 and which involve ternary enzyme/ATP/Mg2+ complexes,20 no studies of the stability of low molecular weight ternary complexes containing Mg2+ and ATP have been reported, although the temperature-jump method has been used in a kinetic study2] of ternary complexes containing 8-hydroxyquinoline, Mg2+, and ATP. Measurement of stability constants of ternary complexes of ATP, a transition metal ion, and 2,2'-bipyridyI,** or trypt~p h a n~~ showed that these complexes are rather stable.Stacking between the purine moiety of ATP and bipyridyl or tryptophan in the ternary complexes Zn(ATP)(bpy)2-and z n ( A T P ) ( t r~)~-has been observed by IH NMR.23*24 Spectrophotometric s t~d i e s~~-~~ indicate that adducts between a purine derivative and bipyridyl or tryptophan even occur in the absence of a metal ion, although these binary adducts are rather weak. Similar stacked complexes have been observed with m a n g a n e~e ( I I ) ,~~ ~o b a l t ( I I ) ,~~ n i~k e l ( I I ) ,~~ copper-(11),22-24 and z i n~( I I ) ,~~,~~ but Mg2+ and Ca2+ were not studied owing ...

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Section: Determination Of Equilibrium Constants Bymentioning

confidence: 99%

Ternary complexes in solution. 28. Enhanced stability of ternary metal ion/adenosine 5'-triphosphate complexes. Cooperative effects caused by stacking interactions in complexes containing adenosine triphosphate, phenanthroline, and magnesium, calcium, or zinc ions

Mitchell¹,

Sigel²

1978

J. Am. Chem. Soc.

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“…Under acidic conditions, bpy is protonated stepwise from a mono-protonated form (pK 1 =4.25) to a di-protonated form (pK 2 = -0.2) [55]. It has been shown from various spectroscopic analyses [56,57] and theoretical calculations [58] that the free base (2) and mono-protonated species (2•H + ) have a local minimum at s-trans and s-cis conformation, respectively, but the di-protonated species (2•2H + ) has no Chart 4.…”

Section: -3 Modification Of Photophysical Properties By Protonationmentioning

confidence: 99%

Fluorescent Oligopyridines and their Photo-Functionality as Tunable Fluorophores

Mutai¹,

Araki

2007

COC

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Oligopyridines connected through the 2-and 6-positions have long been the subject of continuing interest because of their high ability to interact with metal ions and/or other molecules, and their transition-metal complexes have been intensely studied for decades because of their characteristic photophysical properties. However, relatively few have been known in regard to the photophysical and photo-functional properties of oligopyridine derivatives. From the late 1990s, fluorescent oligopyridines have been of considerable interest as tunable fluorophores by intermolecular interaction, and the design and synthesis of novel oligopyridine derivatives and their application to fluorescent sensors has increasingly been studied. In this article, we will review recent developments of fluorescent oligopyridines and their photo-functionality.

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“…The acidity constants with 2,2'-bipyridyl were taken from a report by LINNELL and KACZMARCZYK 18 for XHjL and from the work of ANDEREGG 19 for XJJL . The values used for diglycine 6 , triglycine 7 , and tetraglycine 7 were determined by KIM and MAR-TELL.…”

Section: The Acidity Constants Of the Ligandsmentioning

confidence: 99%

Ternary Complexes in Solution, XII. Models for Biological Mixed-Ligand Complexes: 2,2′-Bipyridyl-Cu²⁺-Oligoglycine Systems

Sigel

Griesser

Prijs

1972

Zeitschrift Für Naturforschung B

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The stability constants of the binary Cu 2+ complexes of glycine amide, diglycine, diglycine amide, triglycine, and tetraglycine were determined, as were those of the mixed-ligand Cu 2+ systems containing 2,2'-bipyridyl and one of the mentioned oligoglycines. The results evidence that all these complexes have the same structure and, therefore, the binding sites of the ligands have to be the terminal amino group and the oxygen of the neighbored amide group. The stability differences between the ternary and the binary complexes are in agreement with this interpretation. It is of interest to note that these ternary complexes are significantly more stable than expected on statistical reasons. With increasing pH, the amide groups in the binary complexes are successively deprotonated. Thus, with tetraglycine finally all three amide protons are displaced, and the amide nitrogens are bound to the square-planar coordination sphere of Cu 2+ . As in the Cu 2+ -2,2'-bipyridyl 1 : 1 complex, only two coordination positions are left for the binding of the oligoglycine, in the tenary complexes, only one amide group can be deprotonated. An increase in pH with deprotonation of other amide groups leads to a displacement of 2,2'-bipyridyl, i. e. the simple binary complexes result. No evidence could be observed for the coordination of a deprotonated amide group to an apical position of the coordination sphere of Cu 2+ . Additionally, while the displacement of the first amide proton in the several binary Cu 2+ oligoglycine complexes occurs over a large pH range (4 to 7), the deprotonation in all the mixed-ligand complexes takes place at pH approximately 8.In peptides, and probably also in proteins, the deprotonated amide group is one of the important binding sites for the coordination of Cu 2+ 2 . In fact, quite a number of Cu 2+ -peptide complexes, including those with oligoglycines 3-8 , were investigated, and it was shown that the amide proton is lost by the coordination of this metal ion to the amide nitrogen.The aim of the present study was to learn how the coordination tendency between oligoglycines and Cu 2+ is influenced, if two positions are occupied by another ligand in the coordination sphere of the metal ion. In this way, a situation which is analogous to conditions present in biological systems may be simulated. Additionally, it seems important to understand the mutual influence of two ligands bound to the same metal ion, as such mixed-ligand complexes can be considered as models for enzymemetal ion-substrate complexes 9-12 . For example, in galactose oxidase action, the role of Cu 2+ has been suggested to lie in the formation of a ternary complex with the substrates 13 .Recently, it was shown 14 that in the mixed-ligand 2,2'-bipyridyl-Cu 2+ -glycine amide complex, the Requests for reprints should be sent to Priv.-Doz. Dr. HELMUT SIGEL, Institute of Inorganic Chemistry, Spitalstrasse 51, University of Basel, CH-4000 Basel (Switzerland) .amide group may still be deprotonated in the physiological pH range. However, the un...

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ULTRAVIOLET SPECTRA OF [ILL] COMPOUNDS¹

Cited by 100 publications

References 1 publication

Ternary complexes in solution. 28. Enhanced stability of ternary metal ion/adenosine 5'-triphosphate complexes. Cooperative effects caused by stacking interactions in complexes containing adenosine triphosphate, phenanthroline, and magnesium, calcium, or zinc ions

Ternary complexes in solution. 28. Enhanced stability of ternary metal ion/adenosine 5'-triphosphate complexes. Cooperative effects caused by stacking interactions in complexes containing adenosine triphosphate, phenanthroline, and magnesium, calcium, or zinc ions

Fluorescent Oligopyridines and their Photo-Functionality as Tunable Fluorophores

Ternary Complexes in Solution, XII. Models for Biological Mixed-Ligand Complexes: 2,2′-Bipyridyl-Cu²⁺-Oligoglycine Systems

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ULTRAVIOLET SPECTRA OF [ILL] COMPOUNDS1

Cited by 100 publications

References 1 publication

Ternary complexes in solution. 28. Enhanced stability of ternary metal ion/adenosine 5'-triphosphate complexes. Cooperative effects caused by stacking interactions in complexes containing adenosine triphosphate, phenanthroline, and magnesium, calcium, or zinc ions

Ternary complexes in solution. 28. Enhanced stability of ternary metal ion/adenosine 5'-triphosphate complexes. Cooperative effects caused by stacking interactions in complexes containing adenosine triphosphate, phenanthroline, and magnesium, calcium, or zinc ions

Fluorescent Oligopyridines and their Photo-Functionality as Tunable Fluorophores

Ternary Complexes in Solution, XII. Models for Biological Mixed-Ligand Complexes: 2,2′-Bipyridyl-Cu2+-Oligoglycine Systems

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ULTRAVIOLET SPECTRA OF [ILL] COMPOUNDS¹

Ternary Complexes in Solution, XII. Models for Biological Mixed-Ligand Complexes: 2,2′-Bipyridyl-Cu²⁺-Oligoglycine Systems