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.

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.

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.

scholarly journals Synthesis and Spectroscopic Characterization of Two New Dawson Sandwich Complexes: Na18[(NaOH)2(VO)2(P2W15O56)2].40H2O and Na18[(NaOH)2(VO)2(As2W15O56)2].27H2O

2012 ◽  
Vol 9 (4) ◽  
pp. 2185-2190 ◽  
Author(s):  
Mohammad Hakimi ◽  
Mohammad Reza Mohammadi ◽  
Salma Behboupour
Keyword(s):  
Divalent Cation ◽  
31P Nmr ◽  
Spectroscopic Characterization ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Sodium Salts ◽  
Vis Spectroscopy ◽  
Sandwich Type ◽  
Anion Complexes

Reaction of the three vacant complex ofa-[P2W15O56]12-anda-[As2W15O56]12-with divalent cation of VO2+in 1:1 mole ratio yields a previously unknown sandwich-type Wells-Dawson complex; Na18[(NaOH)2(VO)2(P2W15O56)2].40H2O (represented as Na2(VO)2P4W30) and Na18[(NaOH)2(VO)2(As2W15O56)2].27H2O (represented as Na2(VO)2As4W30). These complexes contain anions in which two divalent VO2+cations with two Na+ions are symmetrically sandwiched between two α-[P2W15O56]12- or α-[As2W15O56]12-groups leading to a “lacunary” sandwich complex. The anion complexes are isolated as sodium salts and characterized by elemental analysis, TGA, IR, 31P NMR and UV-Vis spectroscopy.

Fletcher–Powell minimization of analytical potentiometric data by microcomputer: application to the Cu(II) complexes of biological polyamines

1985 ◽  
Vol 63 (11) ◽  
pp. 3122-3128 ◽  
Author(s):  
Douglas M. Templeton ◽  
Bibudhendra Sarkar
Keyword(s):  
Biological Activity ◽  
Metal Complex ◽  
Stability Constants ◽  
Speciation Analysis ◽  
Complex Stability ◽  
Minimization Algorithm ◽  
The Stability ◽  
Best Fit ◽  
Complex Stability Constants ◽  
Potentiometric Data

The Fletcher–Powell minimization algorithm has been successfully implemented for the extraction of metal complex stability constants from analytical potentiometric data. The procedure has been adapted to run on a microcomputer with acceptable execution times, and several strategies are employed to speed convergence and avoid false minima. This allows economical minimization for a large number of models of speciation, and improves the reliability of the proposed best fit by encouraging the checking of more models than previously possible. The Ni(II)–glycine system has been analyzed and excellent agreement with the stability constants of an earlier multi-laboratory study has been attained. The system proves useful in the evaluation of both analytical and computational methods. The procedure has also been used for speciation analysis of the Cu(II) complexes of the growth regulating polyamines, spermine, and spermidine. Both systems form fully deprotonated complexes at physiological pH, which are relevant to their biological activity.

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

Inhibition of Mordant Dyes Destruction in Fenton Reaction

2013 ◽  
Vol 821-822 ◽  
pp. 493-496 ◽  
Author(s):  
Jian Hua Ran ◽  
Irina Shushina ◽  
Viktoriia Priazhnikova ◽  
Felix Telegin
Keyword(s):  
Complex Formation ◽  
Dissociation Constant ◽  
Spectral Method ◽  
Fenton Reaction ◽  
Oxidation Process ◽  
Hydroxyl Group ◽  
Spectral Studies ◽  
Iron Ions ◽  
Relationship Of ◽  
Kinetics Of

Kinetics of destruction of acid and mordant dyes in Fenton reaction was investigated by the use of spectral method. Inhibition of destruction of some mordant dyes was observed. A simple theory for describing this phenomenon was proposed, which is based on consideration of participation of iron ions in complex formation with mordant dye ligands. By the use of chemical software JChem (ChemAxon) it was found that mordant dye exhibiting stability in Fenton solution bears hydroxyl group with high dissociation constant, pK=2,57. On the contrary, another dye bearing hydroxyl with low dissociation constant, pK1=6,65, does not exhibit any inhibition in oxidation process. UV-Vis spectral studies of the complexes of several mordant dyes prove correlations with their stability in Fenton reaction, however some dyes exhibit no relationship of this kind.

Sandwich-Komplexe des Palladiums und Platins [1] / Sandwich Complexes of Palladium and Platinum [1]

1984 ◽  
Vol 39 (1) ◽  
pp. 50-55 ◽  
Author(s):  
Hubert Wadepohl ◽  
Walter Siebert
Keyword(s):  
Sandwich Structure ◽  
Platinum Complex ◽  
Sandwich Complexes ◽  
Nmr Data ◽  
C Nmr

1,3,4,5-Tetraethyl-2-methyl-1,3-diborolene (1) reacts with MX2 (M = Pd, Pt) and Na(C5H5) to give orange-red cyclopentadienyl(1,3-diborolenyl)palladium 3 and the yellow platinum complex 4, respectively. Bis(1,3,4,5-tetraethyl-2-methyl-1,3-diborolenyl)platinum (5) is obtained in low yield from 1, Na(HBEt3) and PtCl2 or from 1 and [(C2H4)PtCl2]2. 1H, 11B, and 13C NMR data of 3, 4, and 5 are in agreement with a sandwich structure. The 16e complex 5 is reduced by potassium to its mono- and dianion.

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