Isomers of 5helicene derivatives containing fluorenyl or tert-butylnitroxide radicals in positions 4 and 11 are studied by density functional theory simulations. It is shown that open forms of such isomers include two almost non-interacting unpaired electrons, while their cyclic forms exhibit diamagnetic states. The results obtained using two DFT functionals (M05-2X, B3LYP-D3BJ) are confirmed by multi-configurational SA-CASSCF/NEVPT2 calculations. A TD-DFT study of electronic spectra indicates the possibility of photoinduced switching between spin states of these compounds. The prospect of using 5helicene as a platform for the design of organic magnetic switches is substantiated.
Starikov et al. (Thu,) studied this question.