A solution of citric acid (H4L) was prepared in water, to a portion of which one selected type of metal chlorides (NaCl, CaCl2, ZnCl2 or CuCl2) was added. To each of these solutions the NaOH solution was added until neutralized. The pH of all solutions rises steadily till pH =7, , with the most obvious difference for Cu2+, for which double amount of NaOH was needed for the neutralization. The most obvious differences were noticed at conductivity measurements, where with a strong electrolyte, namely NaOH was adding, the conductivity steadily rises only for the monovalent sodium ions. On other hand, with the other metal ions (notably divalent) clearly conductivity decreases are seen. These curves are consistent with the anticipated better ability of the divalent metal cations binding to the citric acid anion. These observations were compared to three of the known copper compounds in this system, namely [Cu2(L)(H2O)2]n, (CN3H6)4[Cu2(L)2](H2O)2 and (CN3H6)[Cu2(OH)(L)(CN3H5)2], being synthesized as previously described in resources. The identity of these compounds was confirmed by elemental and powder X-ray analysis, while the IR was applied for the synthesis reproducibility checking.
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