The hydrothermal reaction of an aqueous ammonium heptamolybdate solution with first-row transition metal salts in the presence of 2-aminopyridine at around 180°C and under autogenous pressure yields several molybdates, such as the 1D chains in (C 5 N 2 H 7 ) 4 (3)] The structures of these materials were established by single-crystal and powder X-ray diffraction