We further elaborate these considerations with the calculated energies of the open-shell and closed-shell structures for each helicene scaffold 1a,b (open and closed forms) using CASSCF calculations with an (8,8) active space and the 6-31G(d,p) basis set (see Scheme 2). The energies of the closed form triplet states (CT) of 1a-CT and 1b-CT are significantly higher, by more than 50 kcal mol -1 , than their closed-shell singlet states (CCS) thus supporting a pure closed-shell ground state before irradiation. The diradical character index (y) of this ground state was calculated to 0.003 and 0.004 for 1a-C and 1b-C, respectively, confirming a negligible diradical character (calculated by natural occupation orbital numbers analysis, see the Supporting Information Section S3). In contrast, the open-form helicenes have a triplet ground state (OT) with a calculated ETS,calc of 5 and 8 kcal mol -1 for 1a-O and for 1b-O, respectively. While this calculated value for ETS,1a is different compared to our experimentally determined ETS,1a, the trend of the energy levels is retained. The biradicaloid character of the thermally accessible singlet state OCS is enhanced for the open form which is represented by y values of 0.12 and 0.84 for 1a-O and 1b-O, respectively. Such ground state triplet diradicaloids are rare since the double spin-polarization effect turns the vast majority of diradicals into ground state singlets with a thermally accessible triplet state. However, a triplet ground state, as in our helical switch system, is desirable for obtaining a maximum response of the EPR active form.