ISSN:
1573-1111
Schlagwort(e):
Intramolecular overcrowding
;
crystal structures
;
spherand
;
Li+ complexes
;
host
;
guest
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract The structures of the title novel hosts and host-guest complexes, synthesized by D. J. Cram and his colleagues, were determined by direct methods from diffractometer data and refined by least-squares. The hosts C52H52O8,I, C50H48O6,II, and C52H52O6,III, are di-bridged derivatives of the prototype spherand C48H48O6,IV. InIV, six 4-methylanisole units are joined in the 2,6 positions. InI two -CH2CH2OCH2CH2- bridges replace four of the methoxy methyl groups, joining pseudo-meta oxygen atoms; these two bridges are on the same face of the macrocycle (syn). InII andIII, trimethylene and tetramethylene bridges, respectively, are similarly situated, again replacing four methoxy methyls ofIV. CompoundsIa,IIa andIIIa are Li+ complexes of these hosts. The lithium ion is essentially hepta-coordinated inIa, penta-coordinated inIIa and hexa-coordinated inIIIa. These structures are extremely rigid, and the aromatic rings in them are greatly deformed. There are intramolecular oxygen contacts in each complex only slightly greater than 2.5 Å, about 10 percent shorter than the sum of the usual van der Waals radii for oxygen atoms. Thus the structures provide useful data for parameterizing potential functions for molecular mechanics calculations.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01053873
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