Characterization of the t-Butyl Radical and Its Elusive Anion.

The t-butyl radical and its anion are studied theoretically using state-of-the-art quantum mechanical methods including coupled cluster theory with full single, double, and triple excitations (CCSDT) and CCSDT with perturbative quadruple excitations [CCSDT(Q)], in concert with large correlation-consistent cc-pVXZ and aug-cc-pVXZ (X = D, T, Q, 5) basis sets. The relative energies are extrapolated to the complete basis set limit (CBS). The lowest energy structure of the t-butyl radical has a nonplanar carbon backbone with overall C3v symmetry.