The excited *UO2+2(aq) in its lowest (5f, δu or ϕu), π3u configuration is shown to interact with aquo-metallic complexes Mz+(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))πu–d(Mz+(aq)) overlap and d-to-πu electron transfer, while (*UO2+2(aq))δu, πu–d2 or s2(Mz+(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 Mz+. The expression of the rate constant of the *UO2+2 quenching, via *uranyl(VI)—Mz+ 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)+E0–0(5fâ†�πu). The possibility of electron transfer from species *UO+2(aq) to Mz+(aq), with *UO+2(aq) being formed by hydrolysis of *UO2H2+(aq), is also discussed.