title: Ab initio structures for 90 degrees -twisted s-trans-1,3-butadiene and cyclooctatetraene: the naked sp2-sp2 bond.
abstract: The bond length of a carbon-carbon sp2-sp2 sigma-bond without the perturbing effects of pi-interactions has been estimated by high level calculations on two prototypical systems: a 90 degrees -twisted form of butadiene and the tub conformer of cyclooctatetraene. The former system yields a value of 1.4818 A, considerably longer than previous estimates. The corresponding bond length in the latter is slightly shorter due to some pi-electron delocalization.
authors.forename: David
authors.initials: D
authors.lastname: Feller
authors.forename: Norman C
authors.initials: NC
authors.lastname: Craig
authors.forename: Albert R
authors.initials: AR
authors.lastname: Matlin