Header menu link for other important links
Alteration in the binding property of a laterally nonsymmetric aza cryptand toward CuII, AgI, and TlI ions upon derivatization with a cyanomethyl group
, P.K. Bharadwaj
Published in
Issue: 9
Pages: 1771 - 1776
The laterally nonsymmetric aza cryptand Lo readily forms mononuclear inclusion complexes with metal ions like CuII, Ni II, AgI, TlI, and so forth. However, when the secondary amines present in the three bridges are substituted by a cyanomethyl group to yield a new cryptand L, its metal-binding properties are drastically altered. Thus, while Lo binds AgI at the tren end, showing AgN4 coordination, in L, the bridgehead nitrogen atoms are pulled inside to form a two-coordinate complex of AgI and none of the O or N atoms present in the three bridges are involved in coordination. This is probably the first example where the two bridgehead atoms are pulled inside to the maximum to bind the metal ion. Likewise, the TlI ion shows TlN4 coordination with Lo, while in L it is loosely bound at the tren end, showing TlN3 coordination. Upon treatment with a AgI salt, the TlI can be replaced almost instantaneously. On the other hand, with copper(II) tetrafluoroborate salt in moist DMF, two of the cyanide groups in L are converted to carboxylic acid groups and bind the metal ion from outside. The CuII ion in this complex shows distorted octahedral coordination where the two O atoms from the two carboxylic acid groups and the two corresponding N atoms in the two bridges are bound equatorially. The two axial sites are occupied by the nearby bridgehead N atom and the O atom of a DMF molecule. All five complexes and the free ligands are characterized by spectroscopic and X-ray crystallographic studies. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
About the journal
Published in
Open Access
Impact factor