[Fe(bpy) 3 ] 2+ (bpy = 2,2'-bipyridine) is a true TM-based prototype for excited-state dynamics. It is known from several investigations utilizing various experimental techniques that this complex undergoes light-induced low-spin (LS, singlet) → high-spin (HS, quintet) transition in < 100 fs. The LS → HS transition is accompanied by ∼ 0.2 Å elongation of the Fe-N bonds, as well as changes in the solvation (hydration) structure. Interestingly, AIMD simulations utilizing density functional theory (DFT) led to contradictory results: in the HS state, two water molecules were expelled from the first solvation shell when utilizing the BLYP exchange-correlation (XC) functional, while two molecules enter the first solvation shell, when using the same functional but including D3 dispersion correction (BLYP-D3 ). These results highlight the importance of long-range dispersion, which is a known failure of standard XC functionals, for the description of solvation. Furthermore, it was shown for [Fe(bpy) 3 ] 2+ that the dispersion-corrected AIMD solvation cages are more consistent with X-ray scattering data than those obtained by classical MD with partial charges on the complex that reproduce the molecular electrostatic potential. Indeed, significant differences are observed between solvation structures simulated by AIMD and those relying on MM models, i.e., QM/MM and classical MD, in particular, the AIMD shells are more structured. In general, there is a high demand for FF-based simulation techniques more efficient than AIMD but with improved accuracy. In order to reach this goal, it is crucial to gain a thorough understanding on the theoretical description of solute-solvent and solvent-solvent interactions.