The complete synthesis procedure can be found elsewhere . The different salts were dissolved in deionized water as stock solutions, which were further diluted for the experiment. For further discussion on the (Ni,Co)-mixtures, where specifically c(Ni 2+ + Co 2+ ) = 0.02 M, c(DAP) = 0.1 M, we define Ni numbers (Ni#) as they are used (see Eq. [1]) from 0.1 (Co-rich) to 0.9 (Ni-rich).