ISSN:
0018-019X
Schlagwort(e):
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The crystal structures of four anion cryptates [X- ⊂ BT-6H+] formed by the protonated macrobicyclic receptor BT-6H+ with F-, Cl-, Br- and N3- have been determined. They provide a homogeneous series of anion coordination patterns with the same ligand. The small F--ion is tetracoordinated, while Cl- and Br- are bound in an octahedron of H-bonds. The non-complementarity between these spherical anions and the ellipsoïdal cavity of BT-6H+ is reflected in ligand distortions. Structural complementarity is achieved for the linear triatomic substrate N3-, which is bound by two pyramidal arrays of three H-bonds, each interacting with a terminal N-atom of N3-. The formation constants of the complexes formed by BT-6H+ with a variety of anions (halides, N3-, NO3-, carboxylates, SO42-, HPO42-, AMP2-, ADP3-, ATP4-, P2O74-) have been determined. Very strong complexations are found, as well as marked electrostatic and structural effects on stability and selectivity; in particular the binding of F-, Cl-, Br-, and N3- may be analyzed in terms of the crystal structure data. The cryptand BT-6H+ is a molecular receptor containing an ellipsoïdal recognition site for linear triatomic substrates of size compatible with the size of the molecular cacity. Further developments of various aspects of anion coordination chemistry are considered.
Zusätzliches Material:
5 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/hlca.19840670112
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