Fluoride ion receptors: A comparison of a polyammonium monocycle versus its bicyclic corollary

Two polyammonium macrocyclic receptors, the monocyclic 3,6,9,17,20,23 - hex aazatricyclo [23.3.1.1(11,15)]triaconta - 1(29),11,13,15(30),25,27 -hexaene (L-1) and its bicyclic analog 1,4,12,15,18,26,31,39-octaazapentacyclo[13.1 3.13.1(6,10).1(20,24).1(33,37)] - tetratetraconta-6,7,9,20(43),21,23,33(42) ,34,36-nonaene (L-2), have been synthesized as their hexatosylate salts. Th e propensity for binding fluoride ion was examined using both NMR and poten tiometric techniques. The fluoride salts of both receptors have been charac terized by X-ray crystallographic methods. For the monocycle, the complex c rystallized as the mixed fluoride-bifluoride salt, [H6L1](6+).4F(-).2FHF(-) .4H(2)0, and the bicycle crystallized as a complex salt, [H6L2](6+).F-.2FHF (-).1.5SiF(6)(2-).7H(2)O.