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Titolo:
STRUCTURE-REACTIVITY RELATIONSHIP IN INTERLOCKED MOLECULAR-COMPOUNDS AND IN THEIR SUPRAMOLECULAR MODEL COMPLEXES
Autore:
ASAKAWA M; BROWN CL; MENZER S; RAYMO FM; STODDART JF; WILLIAMS DJ;
Indirizzi:
UNIV BIRMINGHAM,SCH CHEM,POB 363 BIRMINGHAM B15 2TT W MIDLANDS ENGLAND UNIV BIRMINGHAM,SCH CHEM BIRMINGHAM B15 2TT W MIDLANDS ENGLAND UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,DEPT CHEM LONDON SW7 2AY ENGLAND
Titolo Testata:
Journal of the American Chemical Society
fascicolo: 11, volume: 119, anno: 1997,
pagine: 2614 - 2627
SICI:
0002-7863(1997)119:11<2614:SRIIMA>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
POLYROTAXANES; CARBOXYLATE; CATENANES; ROTAXANES; SYN;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
33
Recensione:
Indirizzi per estratti:
Citazione:
M. Asakawa et al., "STRUCTURE-REACTIVITY RELATIONSHIP IN INTERLOCKED MOLECULAR-COMPOUNDS AND IN THEIR SUPRAMOLECULAR MODEL COMPLEXES", Journal of the American Chemical Society, 119(11), 1997, pp. 2614-2627

Abstract

Examination of the pseudorotaxane-like geometries adopted in the solid state by a series of 1:1 complexes revealed significant differences in the hydrogen bonding interactions between oxygen atoms in some hydroquinone-based guests carrying polyether/polyester functions and the acidic hydrogen atoms on the bipyridinium units of the host-cyclobis(paraquat-p-phenylene). These differences are reflected directly in the stabilities of the complexes in solution and dramatic changes in the magnitudes of their association constants (K-a values ranging from 130 to 4300 M(-1) in MeCN at 25 degrees C) are observed upon varying the location of the carbonyl ester function(s) along the polyether/ester chains. A similar effect (K-a values ranging from 5 to 730 M(-1) in Me(2)CO at 25 degrees C) was observed in the binding of paraquat as its bipyridinium bis(hexafluorophosphate) salt by analogous macrocyclic hydroquinone-based mono- and bis-lactones. Investigations of the kinetics of hydrolyses of the ester functions revealed that - while inert in their free forms - the macrocyclic mono- and bis-lactones undergo hydrolysis when incorporated within [2]catenanes composed of one of these macrocyclic lactones and cyclobis(paraquat-p-phenylene). Presumably, the enhanced reactivity of the ester functions is a result of [C-H ... O] hydrogen bonding interactions involving the ester carbonyl oxygen atoms and the acidic hydrogen atoms on the bipyridinium units, as suggested by single-crystal X-ray crystallographic analyses. Thus, cyclobis(paraquat-p-phenylene) can act as a mechanically-interlocked ''catalyst''.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 25/01/20 alle ore 06:22:57