The syntheses and free energies of association of 12 new macrocyclic ligand systems (hosts) with alkali metal and ammonium and alkylammonium picrates in CDCI3 are reported at 25°C. Ten of the hosts were composed of 4-methylanisole units (abbreviated AN) incorporated into the macroring by substitution at their 2,6 positions by CH2O (MO) units, or by direct attachment to other AN units at their 2,6 positions. The macrorings were completed with CH2CH2 (E) units and additional ether oxygens (O). Their structures were AN(MOEO)2E (22), AN(MOEOE)2O (23), AN(MOEOEO)2E (24), AN-(MOEOM)2AN (31), AN(MOEOEOM)2AN (32), ANAN(MOEO)2E (33), ANAN(MOM)2ANAN (35), ANAN-(MSM)2ANAN in which S is sulfur (36), ANANAN(M0E)20 (37), and ANANAN(MOM)2AN (38). The other two ligand systems were (AN)2DP(OEOEO)2E (39) and DP(OEOEO)2E (40), in which DP = 5,5'-dimethyldiphenyl substituted in the 2,2' positions with O and the 3,3'positions with either H or 2-methoxy-5-methylphenyl (AN) groups. These systems were compared with model macrocyclic ethers not containing anisole units. Generalizations are as follows. The -AGav° of association of hosts (kcal/mol) in CDCI3 with Li+, Na+, K+, Rb+, Cs+, and NH4+ picrates allowed the hosts to be graded as general ligand systems as follows: ANANAN(MOE)2O (10.2); dicyclohexano-18-crown-6 (9.3); (AN)2DP(OEOEO)2E (9.0); 2,3-naphtho-18-crown-6 (8.7); ANAN(MOEO)2E (8.2); DP(OEOEO)2E (7.1); AN(MOEOE)2O (7.0); AN-(MOEOEO)2E (6.6); ANANAN(MOM)2AN (5.8); 1,3-benzo-18-crown-5 (5.7); AN(MOEO)2E (5.5); AN(MOEOEOM)2AN (5.0); AN(MOEOM)2AN (4.5); ANAN(MOM)2ANAN (4.4); ANAN(MSM)2ANAN (4.1). General ion selectivity of each ligand system was measured by the difference in free energies between the best and poorest bound of the picrate salts, -A(AGmax) (kcal/mol). The order was as follows: ANANAN(MOE)2O (5.3), Na+>Li+; (AN)2DP(OEOEO)2E (4.8), K+>Li+ ; 2,3-naphtho- 18-crown-6 (4.8), K+>Li+; 1,3-benzo-18-crown-5 (4.2), NH4+>Li+; dicyclohexano-18-crown-6 (4.1), K+>Li+ ; ANANAN(MOM),AN (3.8), Na+>Li+ ; ANAN(MOEO)2E (3.3), K+>Li+: AN(MOEO-EO)2E (3.2), Cs+>Li+; AN(M0E0E)>O (3.1). K+>Li+; DP(OEOEO)2E (2.6). K+>Li+; AN(MOEOEOM),AN (1.6). K+>Li+; ANAN(MSM)2ANAN (1.1), K+>NH4+; AN(MOEO)2E (1.0), K+>Li+ ; AN(MOEOM)2AN (0.9). K+>Li+. These results demonstrate that, when the oxygens of anisole units are held in sterically enforced conformations which make the unshared electron pairs provide the lining of partially spherical cavities, the anisole units become better and more selective complexers of anions than the now classic crown ether compounds. Such conformations are observed only when w-tcr-anisyl units are incorporated in macroring systems. Copyright © 1979, American Chemical Society. All rights reserved.
