In this work, we apply the FDE-diab methodology to reliably calculate spin-density distributions and to assess the hinge model for the donor in PSII. To that end, we calculate a complex of the radical cation [Chl a] +• with both protonated and deprotonated axial His moiety for different intermolecular angles and displacements. For comparison purposes, we repeat similar computations for hinge-like models from PSI and the bacterial RC of the purple bacterium Rhodobacter sphaeroides. Additionally, we investigate the roles of the protonation state ot the His residue and truncation of the long Chl a hydrocarbon tail as well as the influence of the surrounding protein environment on the resulting spin distributions.