Co-host: The Chemical Society of Japan, The Society of Synthetic Organic Chemistry, Japan (Cooperation)
In the past decade, we have investigated substituent (X) effects at C(2) on the ground-state spin multiplicity of cyclopentane-1,3-diyls DR1 (Y = H), and found that the ground-state spin multiplicity of 2-alkoxy (X = OR) or 2-silyl (X = SiR3)-1,3-diyls is singlet state. In this study, we investigated computationally the singlet-triplet energy gap in 1,3-diyls that possess electron-withdrawing (DR2, Y = CF3) or donating group (DR3, Y = OMe) at C(1) and C(3). Consequently, we found that the energy gap in DR2 (X = OMe, Y = CF3) was calculated to be smaller than DR1 (X = OMe, Y = H). Alternatively, the energy gap in DR2 (X = SiH3, Y = CF3) was computed to be larger than DR1 (X = SiH3, Y = H). In the diradicals DR3 (Y = OMe), however, we found that the energy gap of 2-alkoxy-substituted diyls is calculated to be larger than DR1. It should be noted that the 2-silyl-substituted diradical DR3 was calculated to be the triplet ground state moles.
