A regioselective route to new polytopic receptors by diaminolysis of chlorocyclotriphosphazatriene-containing crown ethers

A general strategy is reported for the facile preparation of diamino-derivatized PNP-crowns, giving access to a large range of new host molecules of different sizes, shapes, and topology. Reactions of the tetrachloro-PNP-crown precursor 1 with polymethylene-diamines 2a-h (n = 2-6, 8, 10, 12) proceed rapidly and regioselectively via substitution reactions of CI at the PNP-crown-forming P-atoms; the reaction is assisted by the macrocyclic 1,3-oxy(tetraethylenoxy) substituent at the N3P3 ring which provides a site for the hydrogen-bond-driven assembly of reagents 1 and 2. The products belong to three different classes of polytopic receptors: lateral macrobicycles (ansa, 5a-h), bola-amphiphilic tritopic bis-crowns (bino, 6a-h), and tetratopic cylindrical. macrotricycles (bis-bino, 8a-h). The structures of 5, 6, 8, and 10b were established by MS and P-31 NMR spectroscopy, and an X-ray crystal structure was obtained for the bis-bino 1,3-diaminopropane PNP-crown derivative 8b. Preliminary screening by a simple TLC test of the metal-cation complexing properties of the series of compounds 5, 6, and 8 revealed their capacity to bind both harder (alkali and alkaline earth) and softer (transition) metal cations, with significant affinity being displayed toward potassium and silver cations by many of the ligands studied.