The excited *UO²⁺_2(aq) in its lowest (5f, δ_u or ϕ_u), π³_u configuration is shown to interact with aquo-metallic complexes M^z+_(aq) to form, after solvent and ligand shell reorganisations, intimate pairs with the two ions in contact, probably surrounded by a common shell of water molecules. A favourable arrangement of the two aquo-ions in the intimate pair is shown to require little reorganisation for consecutive (*UO²⁺_2(aq))π_u–d(M^z+_(aq)) overlap and d-to-π_u electron transfer, while (*UO²⁺_2(aq))δ_u, π_u–d² or s²(M^z+_(aq)) overlaps require additional ligand shell reorganisation. The decomposition of the (UO⁺₂—M^{(z+ 1)+})* exciplexes to (UO⁺₂—M^{(z+ 1)+}) solvated ion pairs which subsequently dissociate into solvent-separated ions UO⁺_2(solv) and M^{(z+ 1)+}_(solv), competes strongly with the direct decay of the exciplexes to give UO²⁺₂ and M^z+. The expression of the rate constant of the *UO²⁺₂ quenching, via *uranyl(VI)—M^z+ pair–exciplex–uranyl(V)—M^{(z+ 1)+} pair, is checked quantitatively. By means of this expression, the standard redox potential E^°(*UO²⁺₂/UO⁺₂) is found to be 2.61 V, which is in agreement with the value given in the literature 2.60 V = 0.06 + 2.54 =E^°(UO²⁺₂/UO⁺₂)+E_0–0(5fâ†�π_u). The possibility of electron transfer from species *UO⁺_2(aq) to M^z+_(aq), with *UO⁺_2(aq) being formed by hydrolysis of *UO₂H²⁺_(aq), is also discussed.