To gain more insight into the measured spectra, detailed computations of the electronic structure of the anions 1 and 2 proved to be indispensable (see also supporting information Section S3). We carried out ab initio computations using complete active space self-consistent field (CASSCF) and CAS second-order perturbation theory (CASPT2) methods, followed by spin-orbit configuration interaction (SO-CI) computations. These computations were based on the crystal structures, reoptimized at the density functional theory (DFT) level with periodic boundary conditions. We also performed DFT optimizations of the isolated complex ions, which did not lead to any significant change of the structures.