Enclathration by Werner Hosts: Selectivity and Polymorphism

The structures of six inclusion compounds with the two isomers of methylnaphthalene and the Werner host Ni(NCS)(2)(4-phenylpyridine)(4) were determined. We report on the polymorphism and concomitant color change of the 1-methylnapthalene clathrates and the formation of a host dimer in a 2-methylnapthalene clathrate. We investigated the selectivity of the host toward an equimolar mixture of the naphthalene isomers and found that the selectivity varies from 87% 1-methylnapthalene to 54% 1-methylnapthalene with time and increasing evaporation of cosolvent, rendering a labile system.