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[2.n](2,6)Pyridinocrownophanes (3a-e) were efficiently prepared by intramolecular [2 + 2] photocycloaddition of vinylpyridine derivatives under irradiation using a 400-W high-pressure mercury lamp through a Pyrex filter. They were of cis-configuration with respect to the cyclobutane ring, which was proven by the specific methine proton NMR resonances at delta 3.98-4.08. From ESI-MS analysis 3a-e were found to form 1:1 complexes with Ag+ cation. In a liquid-liquid extraction, 3 showed the highest affinity toward Ag+ cation among several heavy metal nitrates. In this series, 3c possessing four ethereal oxygen atoms was found to show the highest Ag+ affinity, according to the liquid-liquid extraction and determination of stability constant with the cation. The photoreactivity of precursor vinylpyridines is discussed by the predictor gamma(r(c)) proposed by Caldwell.

Synthesis and Complexing Properties of [2.n](2,6)Pyridinocrownophanes. -The title compounds (I) form 1:1 complexes with the cation Ag + , but do not undergo complexation with Pb 2+ , Cu 2+ , Mn 2+ , Zn 2+ , Ni 2+ , and Co 2+ . -(INOKUMA, S.; IDE, H.; YONEKURA, T.; FUNAKI, T.; KONDO, S.-I.; SHIOBARA, S.; YOSHIHARA, T.; TOBITA, S.; NISHIMURA*, J.; J.