Abstract
The ground state of the parent trimethylenemethane (TMM) is planar in stereochemistry. The alternative bisected form is a just metastable species. From this perspective, most of TMM derivatives are assumed to be planar in the ground state. Recently, however, we found a bisected TMM derivative, 1,1-dianisyltrimethylenemethane biradical, in the ground state. To gain further insight into stereochemistry of TMM derivatives, we observed UV/Vis absorption and fluorescence spectra of some TMM and related compounds, generated by photolysis or gamma-ray irradiation of low temperature matrices of the corresponding precursors. Furthermore we performed calculation study using density functional theory (DFT) method. We proposed that the diphenyl-substituted five-membered cyclic trimethylenemethane have a twisted conformation in the ground state.
