New molecular receptors for organics of biological interest for the facilitated transport in liquid and solid membranes

Membrane mediated transport of organics by liquid or fixed-site complexant membranes are presented. Multiple molecular recognition represents a key function of polytopic receptors. These compounds with a specific geometry by an adequate arrangement of binding sites present different non-covalent interactions with the solute. Thus, the organic solute can be strongly entrapped and well partitioned in membrane media. Multiple molecular recognition of zwitterionic L-phenylalanine by a bis-macrocyclic receptor provided an active transport mechanism in liquid membranes, as function of the nature of co-transported alkaline cation (Li+, Na+ or K+). Facilitated transport by macrocyclic fixed site complexant membranes is presented for different organics of biological interest (amino acids and organic acids). It resulted from new multiple molecular recognition principles in solid medium, yielding to a dual mode transport. A cooperative electrical membrane potential generated by the symport of protons, controlled and increased the selectivity of fixed-site macrocyclic complexant membranes. These membranes presented a long life time which overcomes the instability of liquid membranes. (C) 2001 Elsevier Science B.V. All rights reserved.