M. Saadioui et al., SYNTHESIS AND CHARACTERIZATION OF 2 AZOBENZENE MODIFIED 1,3-CALIX[4]-BIS-CROWNS AS ARTIFICIAL POTENTIALLY ALLOSTERIC SYSTEMS, Tetrahedron letters, 38(7), 1997, pp. 1187-1190
Azo calix[4]crowns1-[2,2'] and 1-[4,4'] have been synthetized consisti
ng in unsymmetrical 1,3-calix[4]-bis-crowns combining one polyether cr
own-6 and one arobenzene modified crown-6 O-attached at each side of a
calix[4]arene in the 1,3-alternate conformation. Preliminary complexa
tion of alkalis and ammonium picrates showed the cations to be located
in the unmodified crown ether of the 1:1 complexes. Complexation indu
ced changes in the trans/cis ratio of the azobenzene unit of 1-[4,4']
by an allosteric mechanism probably due to conformational changes. (C)
1997, Published by Elsevier Science Ltd.