Here, we report a coupled set of light-dependent and light-independent reaction equilibria which control the mono- or di-metal-functionalization of a prototype molecular vanadium oxide cluster. Comprehensive mechanistic analyses show that coordination of a Mg²⁺ ion to the species {(NMe₂H₂)₂[V^V₁₂O₃₂Cl]}^3- results in formation of the mono-functionalized {(NMe₂H₂)[(MgCl)V^V₁₂O₃₂Cl]}^3- with simultaneous release of a NMe₂H₂⁺ cation. Irradiation of this species with visible light results in one-electron reduction of the cluster shell, exchange of the second NMe₂H₂⁺ with Mg²⁺, and formation / crystallization of the di-metal-functionalized [(MgCl)₂V^IVV^V₁₁O₃₂Cl]^4-. Mechanistic studies show how stimuli such as light or competing cations affect the coupled equilibria. Transfer of this synthetic concept to other metal cations is also demonstrated, highlighting the versatility of the approach.

Left: Illustration of the di-Mg-functionalized polyoxovanadate species {Mg₂V₁₂}.
Right: Illustration of the light-independent and light-dependent coupled reaction equilibria.