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

Reaction of N,N'-bis(salicylidene)-1,4-phenylenedimethanamine with copper(I I) acetate under high-dilution conditions at room temperature in methanol y ielded a dimetallocyclophane in 85% yield. In the crystal structure of the dimeric complex, two rotational isomers of the phenylene bridging groups we re observed. For one isomer, the nearly parallel arrangement of these group s provided a cavity with dimensions 7.31 x 5.23 Angstrom. The rings were ex actly perpendicular in the second rotational isomer. The distance between r ing centers in this perpendicular arrangement is identical to the optimized value for the edge-to-face CH-pi interaction determined by molecular dynam ics calculations for liquid benzene, suggesting a strong edge-to-face inter action in this rotational isomer.