Triplet ground state tetramethyleneethane

More recently, however, the ground spin states of some alternant hydrocarbons have been found to be contradictory to the Longuet-Higgins prediction. For example, whereas the ground state is predicted to be a triplet for tetramethyleneethane [12], and triplet signals have been observed for the parent and the derivatives (Dowd, 1979 Dowd et al., 1896, 1989 Roth et al., 1987), it is difficult to establish triplet ground states experimentally (Du and Borden, 1987). /M,w -Biphenyldicarbene [13] is predicted to have a ground... 

Also dating from that period was the synthesis of another of the Longuet-Higgins molecules, tetramethyleneethane (5), which Dowd " reported in 1970 and assigned a triplet ground state in 1986 in view of its linear Curie plot. We discuss this molecule and its derivatives in Section 7. 

Nash, J. J. Dowd, P Jordan, K. D. Theoretical study of the low-lying triplet and singlet states of diradicals prediction of ground-state multiplicities in cyclic analogs of tetramethyleneethane, 7. Am. Chem. Soc. 1992,114, 10071-10072. 

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