Structures and strain energies of small [n]metacyclophanes.
The structures and strain energies of various derivs. of - and metacyclophanes were computed by employing the d. functional method (ADF). They showed a good agreement with the few available x-ray crystal structures. The structure of 9,12-dichlorometacyclophane was exptl. detd. at 200/233 K. Contrary to intuition, the incorporation of sp2-hybridized C atoms in the oligomethylene chain has a minor influence only on the structure and strain energy of these compds. Small metacyclophanes with potentially interesting interactions between unsatd. fragments in the bridge and the arom. ring or between 2 arom. rings, e.g. the so far elusive [1.1]metacyclophane, are realistic synthetic targets.
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