Bis(monoazacrown ether)s: Effects of bridge length and ring size on stability and selectivity in alkali ion sandwich complex formation

1991 ◽  
Vol 56 (7) ◽  
pp. 1482-1488 ◽  
Author(s):  
Petr Holý ◽  
Juraj Koudelka ◽  
Martin Bělohradský ◽  
Ivan Stibor ◽  
Jiří Závada
Keyword(s):  
Complex Formation ◽  
Homologous Series ◽  
Ring Size ◽  
Azacrown Ether ◽  
Sandwich Complex ◽  
Sodium Potassium ◽  
Alkali Ions ◽  
Potassium Complex ◽  
Bridge Length ◽  
Alkali Ion

Sodium, potassium, rubidium and caesium ion complex formation was investigated in two homologous series of bis(azacrown ether)s Ia-Ic and IIa-IIc. Three complementary bis(azacrown ether)s series IIIa-IIIc, IVa-IVc and Va-Vc were employed for a more detailed study of sodium complexation. Very pronounced effects of bridge length as well as macroring size were found in the investigated series and interpreted mainly in terms of various proclivity of individual ligands and alkali ions to sandwich complex formation. Remarkably high selectivities in alkali ion formation were noted for the shortest bridge ligands Ia and Ib, the former preferring strongly sodium and the latter potassium complex formation.

1,2-Bis(azacrown)ethanes: Effect of Bridge Substitution and Ring Size on Formation of Sandwich Complexes with Sodium and Potassium Ions

1993 ◽  
Vol 58 (1) ◽  
pp. 153-158 ◽  
Author(s):  
Martin Bělohradský ◽  
Petr Holý ◽  
Juraj Koudelka ◽  
Jiří Závada
Keyword(s):  
Complex Formation ◽  
Homologous Series ◽  
Potassium Ions ◽  
Ring Size ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Symmetry Violation ◽  
Title Problem ◽  
Sodium And Potassium

The title problem was investigated potentiometrically using four homologous series of bis(azacrown)s I-IV. A surprisingly large destabilizing effect of bridge substituent was found in the intramolecular sandwich complex formation and ascribed to symmetry violation.

Anion effect on alkali ion-crown complex formation in a moderately concentrated solutions: A sensitive probe of hidden interionic interactions operating in dissociating protic solvents

1990 ◽  
Vol 55 (5) ◽  
pp. 1149-1161
Author(s):  
Jiří Závada ◽  
Václav Pechanec ◽  
Oldřich Kocián
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Charge Density ◽  
Macrocyclic Ligand ◽  
Simple Explanation ◽  
Anion Effect ◽  
Protic Solvents ◽  
The Individual ◽  
Alkali Salts ◽  
Alkali Ion

A powerful anion effect destabilizing alkali ion-crown complex formation has been found to operate in moderately concentrated protic (H2O, CH3OH, C2H5OH) solution, following the order HO- > AcO- > Cl- > Br- > NO3- > I- > NCS-. Evidence is provided that the observed effect does not originate from ion-pairing. A simple explanation is provided in terms of concordant hydrogen bond bridges of exalted stability between the gegenions, M+···OR-H···(OR-H)n···OR-H···A-. It is proposed that encapsulation of alkali ion by the macrocyclic ligand leads to a dissipation of the cation charge density destroying its ability to participate in the hydrogen bond bridge. An opposition against the alkali ion-crown complex formation arises accordingly in the solution in dependence on strength of the hydrogen bridge; for a given cation, the hydrogen bond strength increases with increasing anion charge density from NCS- to HO-(RO-). It is pointed out, at the same time, that the observed anion effect does not correlate with the known values of activity coefficients of the individual alkali salts which are almost insensitive to anion variation under the investigated conditions. As a resolution of the apparent paradoxon it is proposed that, in absence of the macrocyclic ligand, the stabilizing (concordant) bonding between the gegenions is nearly balanced by a destabilizing (discordant) hydrogen bonding between the ions of same charge (co-ions). Intrinsic differences among the individual salts are thus submerged in protic solvents and become apparent only when the concordant bonding is suppressed in the alkali ion-crown complex formation.

Bis(monoazacrown ethers) with an electron-donating substituent at the hinge: A pronounced participation of hydroxyl group in formation of sodium ion sandwich complexes

1989 ◽  
Vol 54 (4) ◽  
pp. 1043-1054 ◽  
Author(s):  
Jiří Závada ◽  
Juraj Koudelka ◽  
Petr Holý ◽  
Martin Bělohradský ◽  
Ivan Stibor
Keyword(s):  
Complex Formation ◽  
Sandwich Structure ◽  
Sodium Ion ◽  
Hydroxyl Group ◽  
Complex Stability ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Marked Enhancement ◽  
Stability Data ◽  
Potentiometric Data

Sodium ion complex formation has been investigated potentiometrically in four homologous bis(crown) series I-IV differing by the nature of substituent placed at the linking trimethylene chain (X = OH, OCH3, OCH2C6H5 and H respectively). A marked enhancement of the complex stability has been observed in the bis(crown) series I and attributed to participation of the lateral hydroxyl group in the sandwich complex formation. Evidence in support of the sandwich structure has been provided (i) by analysis of the potentiometric data indicating a 1:1 complex stoichiometry and (ii) by a comparison of the complex stability data from the bis(crown) series I with the corresponding values from related monocyclic ligand series V, VI and VII revealing a pronounced cooperation of both macrorings in the sodium ion-bis(crown) I complex formation.

Real time monitoring of thrombin interactions with its aptamers: Insights into the sandwich complex formation

2013 ◽  
Vol 40 (1) ◽  
pp. 186-192 ◽  
Author(s):  
Camille Daniel ◽  
Feriel Mélaïne ◽  
Yoann Roupioz ◽  
Thierry Livache ◽  
Arnaud Buhot
Keyword(s):  
Complex Formation ◽  
Real Time ◽  
Real Time Monitoring ◽  
Sandwich Complex

Search for New Thermoelectric Materials through Exploratory Solid State Chemistry. The Quaternary Phases A1+xM3−2xBi7+xSe14, A1−xM3−xBi11+xSe20, A1−xM4−xBi11+xSe21 and A1−xM5−xBi11+xSe22 (A = K, Rb, Cs, M = Sn, Pb) and the Homologous Series Am[M6Se8]m[M5+nSe9+n]

2001 ◽  
Vol 691 ◽  
Author(s):  
Antje Mrotzek ◽  
Tim Hogan ◽  
Mercouri G. Kanatzidis
Keyword(s):  
Thermal Conductivity ◽  
Solid State ◽  
Homologous Series ◽  
Three Dimensional ◽  
Solid State Chemistry ◽  
Narrow Gap ◽  
Trivalent Metal ◽  
Alkali Ions ◽  
Single Crystal Structures ◽  
Physico Chemical

ABSTRACTThe compound types A1+xM3-2xBi7+xSe14, A1−xM3−xBi11+xSe20, A1−xM4−xBi11+xSe21 and A1−xM5−xBi11+xSe22 (A = K, Rb, Cs; M = Sn, Pb) form from reactions involving A2Se, Bi2Se3, M and Se. The single crystal structures reveal that they are all structurally related so that they all belong to the homologous series Am[M6Se8]m[M5+nSe9+n] (M = di- and trivalent metal), whose characteristics are three-dimensional anionic frameworks with tunnels filled with alkali ions. The building units that make up these structures are derived from different sections of the NaCl lattice. In these structures, the Bi and Sn (Pb) atoms are extensively disordered over the metal sites of the chalcogenide network, giving rise to very low thermal conductivity. These phases are all narrow gap semiconductors with 0.25 < Eg< 0.60 eV and many possess physico-chemical and charge transport properties suitable for thermoelectric investigations.

The mobility of alkali ions in gases III. The mobility of alkali ions in water vapour

1939 ◽  
Vol 172 (948) ◽  
pp. 51-54 ◽  
Keyword(s):  
Water Vapour ◽  
Infinite Dilution ◽  
Pure Water ◽  
Atomic Weight ◽  
Alkali Atom ◽  
Water Molecules ◽  
Degree Of Hydration ◽  
Alkali Ions ◽  
Alkali Ion

It is known that in electrolytes at infinite dilution the mobility of an alkali ion increases with its mass and this has been attributed by some to a decrease in its degree of hydration as the size of the alkali atom increases. In Part I evidence was obtained, at least in helium and neon, that the average number of water molecules which are attached to an alkali ion when water is present as an impurity also decreases as the atomic weight of the ion increases. As a natural corollary to this work a determination of the mobility of the alkali ions in pure water vapour has been undertaken and is here described. The method and apparatus of Part I was used. The nature of the ion from the source was first verified by running it in a pure gas which was then pumped off and water vapour introduced. The results are shown in fig. 1, where the mobility of the ion is plotted with E/p . For the sake of clearness the results for Rb + are excluded from the graph except at low values of E/p . The remainder of the Rb + graph follows more or less that for Na + .

COMPLEX FORMATION ENTHALPIES OF TETRANACTIN WITH ALKALI IONS IN METHANOL

1979 ◽  
Vol 8 (12) ◽  
pp. 1487-1490 ◽  
Author(s):  
Masaharu Ueno ◽  
Hiroshi Kishimoto
Keyword(s):  
Complex Formation ◽  
Alkali Ions ◽  
Formation Enthalpies
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