Theoretical study of spectroscopic properties of bicyclobutane, tricyclopentane, tricyclohexane, and octabisvalene

Abstract

-The outer-valence ionization potentials, low-lying electronically excited states, and ' J ( c C ) nuclear spin-spin coupling constants of bicyclobutane, tricyclopentane, tricyclohexane, and octabisvalene have been investigated at the ab initio level by using the outer-valence Green function (OVGF), random-phase approximation (RFA), and equations-of-motions (EOM) approaches, which incorporate the main dynamical correlation effects. A comprehensive theoretical prediction of these spectroscopic observables is presented, which shows several interesting aspects stemming from the unique electronic structure of the bridge bond.

Density Functional Theory Study of Ultrashort and Overlong CC Single Bonds and the Lowest Nonbonding C···C Distance

“…34 Moreover, with ab initio equa- tions-of-motion calculations, we have previously shown that this situation also holds in the case of the intercage bond of the still elusive bitetrahedrane, 35 and for the bridging bond in bicyclobutane, tricyclopentane, and related systems. 18,36 On this basis, the present theoretical predictions can be regarded with confidence.…”

“…However, by using the present basis set and DFT perturbational approach, previous investigations have reported a satisfactory reproduction of 1 J (CC) for a variety of organic compounds. , On the other hand, the dominant importance of the FC contribution to “normal” coupling constants 1 J (CC) is well documented in the literature . Moreover, with ab initio equations-of-motion calculations, we have previously shown that this situation also holds in the case of the intercage bond of the still elusive bitetrahedrane, and for the bridging bond in bicyclobutane, tricyclopentane, and related systems. , On this basis, the present theoretical predictions can be regarded with confidence.…”

Ab Initio Methods for the Calculation of NMR Shielding and Indirect Spin−Spin Coupling Constants

“…Galasso has applied his EOM method (see section VI.F) to compute spin-spin coupling constants in a large number of polyatomic moleculesssee ref 268. Most of the recent results are for the 1 J(CC) constants across unusual bonds in hydrocarbons, like the bridgehead bond in propellanes 269 or the ultrashort bond in bitetrahedrane.…”

Excited States and Photochemistry of Bicyclo[1.1.0]butane

“…When reactant BCB is substituted with 13 C at the 2-position, the BD product may result with the 13 C at either middle or end positions. It is possible to devise a scheme where the intermediate from Figure 8 can be invoked to produce an intermediate diradical yielding CB, which subsequently converts to BD with 13 C substituted according to Schemes 1 and 2. But early studies of the isotope effect of hydrocarbons showed that substitution of 13 C for 12 C was small 54 and would have little effect on changing product ratios or accounting for the mechanism of 13 C substitution.…”