Crown ether functionalization of a porphyrin-based molecular square: induction of fluorescence sensitivity to alkali metal cations

A porphyrin-based molecular square (1), prepared by reaction of a dipyridylporphyrin species with Re(CO)(5)Cl and subsequently with Zn-II acetate, was functionalized with 2-(methylene 15-crown-5-ether)-nicotinoyl ester (2). Functionalization was achieved by axially Ligating each of the four available Zn-II sites within the porphyrins. (2) was synthesized by reaction of 2-(hydroxymethyl)-15-crown-5-ether and nicotinoyl chloride in CH2Cl2. Functionalization renders the squares fluorescence emission intensity responsive to added Na+ and, to a lesser extent, K+. (C) 2001 Published by Elsevier Science B.V.