Design, synthesis and crystal structure of a copper dimetallocyclophane complex exhibiting unique rotational isomerism

Abstract

Reaction of N,N′-bis(salicylidene)-1,4-phenylenedimethanamine with copper(II) acetate under high-dilution conditions at room temperature in methanol yielded a dimetallocyclophane in 85% yield. In the crystal structure of the dimeric complex, two rotational isomers of the phenylene bridging groups were observed. For one isomer, the nearly parallel arrangement of these groups provided a cavity with dimensions 7.31 × 5.23 Å. The rings were exactly perpendicular in the second rotational isomer. The distance between ring centers in this perpendicular arrangement is identical to the optimized value for the edge-to-face CH–π interaction determined by molecular dynamics calculations for liquid benzene, suggesting a strong edge-to-face interaction in this rotational isomer.