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 - hexaazatricyclo [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[13.13.13.1(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. The propensity for binding fluoride ion was examined using both NMR and potentiometric techniques. The fluoride salts of both receptors have been characterized by X-ray crystallographic methods. For the monocycle, the complex crystallized as the mixed fluoride-bifluoride salt, [H(6)L(1)](6+).4F(-).2FHF(-).4H(2)0, and the bicycle crystallized as a complex salt, [H(6)L(2)](6+).F(-).2FHF(-).1.5SiF(6)(2-).7H(2)O.