TY - JOUR
T1 - Conductometric determination of the stability constants of the inclusion complexes of alkali cations with [22-DD] diaza crown ether, [211] and [221] cryptands in acetonitrile
AU - Tawarah, Khalid M.
AU - Khasawneh, Mohammad A.
AU - Mizyed, Shehadeh A.
N1 - Funding Information:
This work was supported by Yarmouk University. The authors are grateful to Mr. F. Rawagah for his help in updating the computer program.
PY - 2005/4
Y1 - 2005/4
N2 - An equilibrium study concerning the association of Na+, K +, Rb+ and Cs+ with 4, 7, 13, 18-tetraoxa-1,10-diazabicyclo [8, 5, 5]-eicosane [211], 4, 7, 13, 16, 21-pentaoxa-1, 10-diazabicyclo [8, 8, 5]-tricosane [221] and 4, 13-didecyl-1, 7, 10, 16-tetraoxa-4, 13-diazacyclooctadecane [22-DD] in acetonitrile has been carried out at 25°C by using a conductometric technique. The observed molar conductivity, Λ, of a test solution was found to decrease significantly for mole ratios less than 1:1 upon the addition of the complexing ligand. A model based on 1:1 stoichiometry has been used to analyze the conductivity data. The data have been fitted according to a non-linear least-squares analysis that provides the stability constant, K, and the molar conductivity, Λc, for each cation - ligand inclusion complex. The binding sequences were found to follow the order: Na+ > K+ > Rb+ ≫ Cs+ (K ≈ 0) for [211], Na+ > K+ > Rb+ > Cs+ for [221] and K + > Na+ > Rb+ > Cs+ for [22-DD] complexes. Trends in ionic conductivities of complexed ions are also discussed.
AB - An equilibrium study concerning the association of Na+, K +, Rb+ and Cs+ with 4, 7, 13, 18-tetraoxa-1,10-diazabicyclo [8, 5, 5]-eicosane [211], 4, 7, 13, 16, 21-pentaoxa-1, 10-diazabicyclo [8, 8, 5]-tricosane [221] and 4, 13-didecyl-1, 7, 10, 16-tetraoxa-4, 13-diazacyclooctadecane [22-DD] in acetonitrile has been carried out at 25°C by using a conductometric technique. The observed molar conductivity, Λ, of a test solution was found to decrease significantly for mole ratios less than 1:1 upon the addition of the complexing ligand. A model based on 1:1 stoichiometry has been used to analyze the conductivity data. The data have been fitted according to a non-linear least-squares analysis that provides the stability constant, K, and the molar conductivity, Λc, for each cation - ligand inclusion complex. The binding sequences were found to follow the order: Na+ > K+ > Rb+ ≫ Cs+ (K ≈ 0) for [211], Na+ > K+ > Rb+ > Cs+ for [221] and K + > Na+ > Rb+ > Cs+ for [22-DD] complexes. Trends in ionic conductivities of complexed ions are also discussed.
KW - Alkali metal cations
KW - Azacrown ethers
KW - Conductivity
KW - Cryptands
KW - Macrocyclic compounds
KW - Stability constants
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U2 - 10.1007/s10847-005-2022-y
DO - 10.1007/s10847-005-2022-y
M3 - Article
AN - SCOPUS:21244463566
SN - 0923-0750
VL - 51
SP - 143
EP - 148
JO - Journal of Inclusion Phenomena
JF - Journal of Inclusion Phenomena
IS - 3-4
ER -