Abstract
1,4-Dicyclooctatetraenyl-1,3-butadiyne and p-, m-, and o-di(cyclooctatetraenylethynyl)benzene (1−4, respectively) and their dipotassium salts (12-−42-) in THF-d8 have been synthesized and studied by dynamic NMR spectroscopy. Rate constants for bond shift (kBS) in the neutral cyclooctatetraene (COT) rings of 1−4 and 12-−42- and for intramolecular charge (electron and cation) transfer (kCT) between the dianion and the neutral COT rings in 12-−42- have been determined. 13C NMR chemical shifts and AM1 π-charges as well as the values of kCT are interpreted on the basis of a stronger through-bond interaction between the COT rings in the order 12- ≫ 22- ≥ 42- > 32-. Similarly, kBS decreases in the order 12- ≫ 42- > 22- > 32- on going from 1−4 to the corresponding dianions. Analysis of the AM1 π-charge densities suggests that these differences are primarily due to a through-bond effect with an additional through-space contribution from the electric field of the dianion ring for bond shift in 42-.
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