ISSN:
0749-1581
Keywords:
13C NMR
;
Chemical shifts
;
Crown ethers
;
Conformations
;
Complexes
;
Naphthalene
;
Sodium ion
;
Potassium ion
;
Rubidium ion
;
Cesium ion
;
Binding constants
;
Alkali metal cations
;
Complexation constants
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
13C NMR studies of alkali metal cation complexation by six related crown ethers are described. The crown ethers (and ions studied) were 2,3-naphtho-20-crown-6 (Na+, K+, Rb+, Cs+), 2,3-naphtho-17-crown-5 (Na+, K+, Rb+, Cs+), 2,3-naphtho-14-crown-4 (Na+, K+, Rb+, Cs+), 1,8-naphtho-21-crown-6 (Na+, K+, Rb+, Cs+), 1,8-naphtho-18-crown-5 (Na+, K+, Rb+, Cs+) and 1,5-naphtho-22-crown-6 (K+, Rb+, Cs+). For each crown ethercation combination, 13C NMR spectra were obtained for a number of different ion concentrations in CD3OD. Data were analysed by a non-linear least-squares treatment to give complexation constants and chemical shifts that would result at the limit of complete 1:1 complexation. Analyses of the limiting chemical shifts for a number of carbons indicate regular, cation-dependent trends (for Cs+ through Na+). Deviations from these trends are interpreted as reflecting differences in conformations of crown ether-cation complexes. Conformational differences between cation complexes that occur near the point of naphthalene attachment cause deviations from the trend in the aromatic carbon chemical shifts, while conformational differences further from the naphthalene cause trend deviations only in the crown ether carbon chemical shifts.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260260305
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