Manganese is used in zinc batteries. The chemical reaction that gives energy to zinc batteries is:
Zn(s) + 2 MnO2(s) →ZnO(s) + Mn2O3 (s).
Manganese is also found in the enzyme that catalyzes the initial reaction in photosynthesis, which happens to be:
2 H2O → 4 H+ + 4 electrons + O2
Finally, Manganese forms ions that exist in a variety of oxidation states. Solutions of these ions each have a particular color: Mn2+ is light pink, Mn3+ is red-brown; Mn4+ is brown, Mn5+ is blue, Mn6+ is green and Mn7+ is a deep purple.