MACRORING NEUTRAL MOLECULE COMPLEXATION - SYNTHESIS OF BICONCAVE PYRIDINO HOSTS, COMPLEX-FORMATION, AND X-RAY CRYSTAL-STRUCTURES OF 2 INCLUSION-COMPOUNDS

A series of pyridino macrocycles 1-3(a-e) incorporating rigid bi- and triaryl ether segments in different ring positions have been synthesized. The effect of incorporation of these building blocks into a given macroring framework on the host properties for uncharged-molecule inclusion has been studied. Symmetric 21-membered macrorings 1c, 1d, or 2c, 2d with tri-o-phenylene, tri-2,3-naphthylene, or mixed phenylene naphthylene ether units are efficient hosts in solid-state complexation of dipolar-aprotic and apolar guests such as nitro compounds and nitriles as well as DMF, DMSO, THF, dioxane, or benzene. X-ray analyses of the solid-state complexes of 1d with PhNO2 (1:1) and MeCN (1:1) have been studied. It is shown that the presence of the triaryl ether segment induces a biconcave nonequally sided host conformation suitable for guest inclusion. The packing characterizes the host-guest topologies of the two inclusion compounds to be of (H-bonded) cavitate-type for the MeCN case and of interstitial channel type for the PhNO2 case. A comparative discussion of the present and previous results support the interpretation of hemispherand preorganization for the new host structures.