Crystallographic evidence of side-arm lariat effect in the series of chiral ortho- and para-methoxyphenoxymethyl-15-crown-5 complexes with sodium perchlorate

The single crystals of the NaClO4 complexes with two potential lariat 15-crowns-5 having ortho- or para-methoxyphenoxymethyl side arms were investigated by X-ray analysis in racemic and enantiopure form. Only ortho-derivative demonstrates lariat effect, i.e. the assistance of lateral fragment in cation complexation. No one oxygen atom of para-substituted side arm takes part in guest encapsulation in the solid phase. Whereas the crystals of racemic and enantiopure ortho-substituted crown complexes differ substantially from one another in packing characteristics, racemic and enantiopure complexes of para-derivatives are almost isostructural. This fact indicates that the last chiral complex belong to the rare class of continuous solid solutions of enantiomers.