B2P2 Rings: Through-space π Bond or Stable Diradical? A Theoretical Study

[[abstract]]Theoretical study of a series of B2P2 ring molecules shows that bulky substituent groups facilitate the existence of bond-stretch isomers. With the largest substituent group, the long bond (LB) isomer is more stable and adopts a mainly through-space B-B bond. Among these LB isomers we observed extraordinarily large singlet-triplet energy separation, a small number of effectively unpaired electrons, and the convergence of spin symmetry-broken (UDFT) computations to RDFT. The T 1 diagnostic for the LB isomer of prototype compound obtained at the CCSD/6-311G level of theory is smaller than 0.02. We thus conclude that these B2P2 ring molecules do not characterize as diradicals