Host-guest complexation. 17. Design, syntheses, and complexation of macrocycles containing phosphoryl, pyridine oxide, and urea binding sites

Phosphoryl (P=O), urea (N/sub 2/C=O), pyridine, and pyridine oxide (N ..-->.. O) groups have been incorporated into the ring systems of macrocyclic polyethers. The association constants of the resulting eight new ligand systems toward Li/sup +/, Na/sup +/, K/sup +/, Rb/sup +/, Cs/sup +/, and NH/sub 4//sup +/ picrates in CHCl/sub 3/ were surveyed, and the free energies of association were estimated. The P=O complexing sites were covalently bonded through two attached o-tolyl groups as in the unit RP(O)(C/sub 6/H/sub 4/CH/sub 2/-o)/sub 2/, in which different R groups were attached to phosphorus. The resulting unit, written as RPOD, was attached to two ether oxygens (0), which in turn were connected through CH/sub 2/CH/sub 2/ or E units to form macrocycles. Ligand systems C/sub 6/H/sub 5/POD(OEOE)/sub 2/O (9), C/sub 6/H/sub 5/POD(OEOEO)/sub 2/E (10), o-HO/sub 2/CC/sub 6/H/sub 4/POD(OEOE)/sub 2/O (11), o-CH/sub 3/O/sub 2/CC/sub 6/H/sub 4/POD(OEOE)/sub 2/O (12), CH/sub 3/OPOD(OEOE)/sub 2/O (13), and C/sub 6/H/sub 5/POD(OEO)/sub 2/PODC/sub 6/H/sub 5/ (14 and 15, the syn and anti isomers) were synthesized and examined. The urea complexing site was cyclic, CH/sub 2/(CH/sub 2/N)/sub 2/C = O (abbreviated to UON), and was bonded through its two nitrogens to E units. The cycle prepared and examined was UON(EOEOE)/sub 2/O (16). The pyridine and pyridine oxide complexing sites were bonded through CH/sub 2/ groups in their ..cap alpha..,..cap alpha..' positions to comprise the units ..cap alpha..-CH/sub 2/(C/sub 5/H/sub 3/N)CH/sub 2/-..cap alpha.. and ..cap alpha..-CH/sub 2/(C/sub 5/H/sub 3/NO)CH/sub 2/-..cap alpha.., respectively, the latter of which was abbreviated as POM. The new cycle prepared and examined was POM(OEOE)/sub 2/O (18). The patterns of ..delta..G/sup 0/ values of complexation of these ligand systems were compared to those of 2,3-naphtho 18-crown-6 (19), 2,6-pyrido-18-crown-6 (20), and 1,3-benzo-18-crown-5 (21). The results suggest that those ligand systems whose organization of binding sites before and after complexation are the most similar show the highest structural recognition toward the anions.