In this work, we investigated spin-density distrubutions and electronic couplings in RCs of photosynthetic systems using the recently developed FDE-diab approach . This technique is known to be highly efficient for calculations of large open-shell molecular systems and to effectively avoid the spin-density overdelocalization problem characteristic to standard KS-DFT. Its high sensitivity to changes in molecular structures allowed us to validate a number of hinge-like molecular models for primary electron donors in RCs.