UV-vis spectra UV-vis spectra were calculated for intermediates 2 and 3/3 ′ considering both open-shell singlet and triplet spin states, if open-shell singlet states were obtained. We performed TD-DFT calculations in Gaussian 16, employing the CAM-B3LYP functional and def2-TZVPP basis set (both as implemented in Gaussian) and including 45 states (roots).