Structural constraints for the formation of macrocyclic rhombimines

Rhombimines, macrocyclic tetraimines, have been obtained by the condensation of enantiomerically pure trans- 1,2-diamino-cyclohexane with aromatic dialdehydes connected by a one-atom bridge. The efficiency of the cyclocondensation is dependent upon the nature of the dialdehyde bridge atom: low selectivity was observed and rationalized by computational analysis for sp(2) hybridized bridge atoms. Unusual triple-split exciton Cotton effects were measured and calculated for highly symmetrical, tetrachromophoric rhombimines. (c) 2007 Elsevier Ltd. All rights reserved.