MOLECULAR RECOGNITION OF NUCLEOSIDES AND NUCLEOTIDES BY A WATER-SOLUBLE CYCLO-BIS-INTERCALAND RECEPTOR-BASED ON ACRIDINE SUBUNITS

The macrocyclic bisacridine receptor 1 prepared by diamine-dialdehyde condensation has been found to complex nucleotides strongly in water, The important changes of the fluorescence properties of 1 upon complexation revealed the remarkable ability of the receptor to discriminate between the two types of nucleobase: addition of purine nucleotides produced a strong quenching of the emission whereas a considerable enhancement of the fluorescence intensity was induced by pyrimidine nucleotides. By comparison with the binding properties of the acyclic monochromophoric reference compound 7 these opposite variations of the fluorescence have been interpreted in terms of electronic interaction (pi/pi stacking) and conformational changes of the receptor 1 (increase of the interchromophoric distance), The stability constants were determined by fluorescence measurements and high values ranging from 10(4) to 10(8) M(-1) were obtained for the 1/1 complexes. The selectivities observed were shown to be dependent on both electrostatic and structural factors.