The Mn-doping/decoration of S-containing semiconductor quantum dots (QDs) determine their photochemical properties and are important in the field of artificial photosynthesis. The Mn-mediated charge-transfer kinetics and energetics in composites of the type CdS/ZnS/ZnSe is discussed in the present note. Their redox features seem to involve Mn2+/Mn3+ transitions. The electron cross reactions with the holes generated by the Mn-species in the S-containing QDs are discussed. The events in the photosynthetic process leading to water oxidation to dioxygen are summarily discussed. The relation of the Mn-transitions to the former processes are suggested.