A Novel Crown Ether Derivative for Cooperative Binding of Alkali Metal Ions and Anions. (1).
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Accession number;00A0163508
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| Title;A Novel Crown Ether Derivative for Cooperative Binding of Alkali Metal Ions and Anions. (1). |
| Author;
NISHIZAWA SEIICHI
(Tohoku Univ., Grad. Sch.)
SHIGEMORI KAZUKI
(Tohoku Univ., Grad. Sch.)
TERAMAE NORIO
(Tohoku Univ., Grad. Sch.)
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Journal Title;Abstracts. Symposium on Biofunctional Chemistry
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Journal Code:L0836A
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ISSN:
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VOL.14th;NO.;PAGE.100-101(1999)
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| Figure&Table&Reference; |
| Pub. Country;Japan |
| Language;Japanese |
| Abstract;A new bifunctional receptor for simultaneous complexation of cations and anions is synthesized on the basis of benzo-15-crown-5, functionalized with a thiourea moiety as hydrogen bond donors to recognize anions. The abilities of the receptor to bind anions in the absence and presence of Na+ are studied in CD3CN by 1H NMR titration experiments. When Na+ is bound to the crown moiety, the association constants of Br-, I- and NO3- complexes are increased by a factor of 10, 5 and 11, respectively, as compared with the free receptor. Thermodynamic studies indicate that these large increases in complex stabilities are ascribed primarily to the increased enthalpic gain, while the entropic gain is keptrelatively unchanged. The favorable enthalpic change is probably rationalized by the enhanced host hydrogen bond donor strength due to an electron withdrawing effect of the crown moiety complexed with Na+ and by the intramolecular electrostatic interaction caused by the closely located Na+. Furthermore, the origin of cooperative binding of Na+ ions and anions is discussed in terms of the enthalpy-entropy compensation effect. (author abst.) |
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