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Synthesis, crystal structure of two new ABTS (2,2-azinobis-3-ethyl benzothiazoline-6-sulfonate) hybrid organic–inorganic salts containing Fe3+ or Cu2+ cations is described. Electrochemical oxidation of the diammonium salt (ABTS)(NH4)2·2H2O in presence of FeSO4·7H2O or CuSO4·5H2O in aqueous solutions yields to black single crystals of Fe2O(ABTS)2(H2O)16 and Cu(ABTS)2·(H2O)8. Due to the low thermal stability of three water molecules intercalated in the network, crystal structures were solved at 200 K using a STOE IPDS diffractometer. Cell parameters are: a=8.5635(7) A˚, b=8.69236(6) A˚, c=20.336(2) A˚, α=84.69(1)°, β=82.10(1)°, γ=81.767(9)°, space group P-1 for the iron complex and a=15.691(3) A˚, b=14.474(3) A˚, c=21.552(4) A˚, β=94.60(3)°, space group P21/c for the copper complex. Transition metal cations are in an octahedral coordination with a different condensation, corner-sharing octahedra Fe2O11 dimmers or CuO6 octahedra. Taking in account these structural results, the chemical formula must be written: [Fe2O(H2O)10][ABTS]2·6H2O and [Cu(H2O)5][ABTS]2·3H2O. The crystalline networks are also different; the iron complex salt presents a bidimensional character and the copper one can be considered as a one-dimensional network. Values obtained from bond valence calculations correspond to iron Fe3+ and copper Cu2+. A Mossbauer study shows that iron is in a high spin 3+ oxidation state without any magnetic ordering even at 4 K (isomer shift δ=0.62 mm s−1 and quadrupole splitting ΔE=1.64 mm s−1). [Copyright &y& Elsevier]