Cyclopentane-1,3-diyls, ground-state calculations

Calculations and Experiments on the Ground States of Cyclopentane-1,3-diyls. Our calculations on 2,2-difluoropropane-l,3-diyl (10) led to another prediction that was subsequently tested by us experimentally and confirmed. Both (2,2)CASSCF and SD-CI calculations predict the triplet to be the ground state of propane-1,3-diyl (8) ° and cyclopentane-1,3-diyl (16a), " a cyclic derivative of 8. Prior experiments by Gloss had shown that the ground state of 16a is, in fact, a triplet and Dougherty, Adam, Wirz, and their co-workers found the same to be true for the 1,3-diphenyl derivative (16b) (Fig. 22.12). ... 

Figure 22.12. Cyclopentane-1,3-diyl (16a) has been both calculated " and found to have a triplet ground state, and the 1,3-diphenyl derivative (16b) has also been found to have a triplet ground state. In contrast, calculations on 16c and 16g have predicted both diradicals should have singlet ground states, and experiments on derivatives of 16d, 16e, and 16f found these three diradicals do, in fact, have singlet ground states.

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