general chemical formula MLmXn, where M denotes a seed metal cation, L is a Lewis base ligand and X denotes an anion, m denotes an integer of value 1, 2, or 4 and n denotes an integer of value 1, 2, or 3; and (ii) a photoreactive oxalate compound with the general chemical formula Y3M ((C2O4)3) where Y denotes an alkali metal ion or a quaternary ammonium ion, and M denotes an iron ion or a rutheniu