with linear combination coefficients a and b. This basis of two quasi-diabatic wave functions Φ 1 and Φ 2 can then be used to evaluate the elements of overlap and Hamilton matrices to subsequently solve a generalized eigenvalue problem. The resulting eigenvector elements a and b define the total wave function Ψ and, thus, give an access to calculations of various molecular properties of the radical cation complex [A • • • B] +• . In the following sections, we briefly describe the FDE-diab methodology and show how accurate electronic couplings, long-range excitations, and spin densities can be calculated from the total wave function.