1998 Volume 71 Issue 11 Pages 2661-2668
Dibenzo[3.3]orthocyclophanes ([3.3]OCPs) with a bicyclo[4.4.1]undecane substructure form charge-transfer (C-T) complexes with tetracyanoethylene (TCNE). 3,4 : 8,9-Dibenzobicyclo[4.4.1]undecane (9) and its 11-methylene derivative 8 are flexible molecules and take a chair-boat conformation. Complexes 8- and 9-TCNE exhibit the absorption maximum at ca. 420 nm, which coincides with the value for the TCNE complex of o-xylene. On the other hand, acetal 5, methylcarbinol 6, and dimethylmethylene derivative 7 are rigid, layered [3.3]OCPs with stacked benzene rings. Compounds 5, 6, and 7 form a 1 : 1 complex with TCNE in solution. The absorption maxima of the complexes at ca. 500 nm suggest an enhanced C-T complexation due to a π–π through-space interaction in 5, 6, and 7. A 2 : 1 complex of rigid [3.3]OCP 7 with TCNE crystallized from dichloromethane, while OCP 8 gave a red crystalline 2 : 3 complex with TCNE. X-ray crystallographic analyses of these two complexes is given.
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