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.

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.

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.

scholarly journals Uranium(iv) cyclobutadienyl sandwich compounds: synthesis, structure and chemical bonding

2020 ◽  
Vol 56 (6) ◽  
pp. 944-947 ◽  
Author(s):  
Nikolaos Tsoureas ◽  
Akseli Mansikkamäki ◽  
Richard A. Layfield
Keyword(s):  
Chemical Bonding ◽  
Molecular Structures ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Sandwich Compounds ◽  
Bonding Properties ◽  
Half Sandwich

The synthesis, molecular structures and bonding properties of two uranium(iv) cyclobutadienyl half-sandwich complexes and a doubly activated cyclobutadienyl sandwich complex are described.

Sodium and Potassium Fluxes in the Abdominal Nerve Cord of the Cockroach, Periplaneta Americana L

1961 ◽  
Vol 38 (2) ◽  
pp. 315-322
Author(s):  
J. E. TREHERNE
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Nerve Cord ◽  
Periplaneta Americana ◽  
Unit Area ◽  
Potassium Ions ◽  
Sodium Ions ◽  
Nerve Sheath ◽  
The Central Nervous System ◽  
Sodium And Potassium

1. The influx of sodium and potassium ions into the central nervous system of Periplaneta americana has been studied by measuring the increase in radioactivity within the abdominal nerve cord following the injection of 24NA and 42K. into the haemolymph. 2. The calculated influx of sodium ions was approximately 320 mM./l. of nerve cord water/hr. and of potassium ions was 312 mM./l. of nerve cord water/hr. These values are very approximately equivalent to an influx per unit area of nerve cord surface of 13.9 x 10-2 M cm. -2 sec.-1 for sodium and 13.5 x 10-12 M cm. -2 sec.-1 for potassium ions. 3. The relatively rapid influxes of these ions are discussed in relation to the postulated function of the nerve sheath as a diffusion barrier. It is suggested that a dynamic steady state rather than a static impermeability must exist across the sheath surrounding the central nervous system in this insect.

Tetanic hyperpolarization of single medullated nerve fibers in sodium and lithium

1976 ◽  
Vol 231 (4) ◽  
pp. 1033-1038 ◽  
Author(s):  
GM Schoepfle
Keyword(s):  
Steady State ◽  
Interspike Interval ◽  
Nerve Fibers ◽  
Repetitive Stimulation ◽  
Time Dependent ◽  
Potassium Ions ◽  
Current Densities ◽  
Medullated Nerve Fiber ◽  
Sodium And Potassium ◽  
Stimulation Of

Repetitive stimulation of a single medullated nerve fiber of Xenopus yields a succession of postspike voltage-time curves which are nearly coincident until attainment of a voltage that corresponds to that of the maximum attained by the normal postspike undershoot. Initially the interspike potential returns toward a resting level after this brief phase of hyperpolarization. However, as tetanization proceeds, a pattern of hyperpolarization develops with the result that, in the tetanic steady state, there exists a progressive hyperpolarization throughout each interspike interval. Extent of postspike hyperpolarization in terms of a deviation deltaVm from the resting level of membrane potential is approximated by the variation deltaVm = delta[MNa + MK]/[GNa + GK] where MNa and MK are current densities associated with active pumping of sodium and potassium ions and GNa and GK are corresponding time-dependent leak conductances. Tetanic hyperpolarization is reversibly abolished by cyanide and by exposure to lithium Ringer. Eventual reappearance of tetanic hyperpolarization in the presence of lithium Ringer suggests lithium pumping.

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