Synthesis, crystal structure and calcination of three novel complexes based on 2-aminopyridine and polyoxometalates

Three novel complexes based on 2-aminopyridine and polyoxometalates (POMs) formulated as (C₅N₂H₇)₅H[P ₂Mo₅O₂₃], 1, (C₅N₂H ₇)₆(H₂O)₂[V₁₀O ₂₈], 2, (C₅N₂H₇)₁₂(H ₂O)₂(CH₃OH)[PMo₁₂O ₄₀]₄, 3, were hydrothermally synthesized and structurally characterized by elemental analysis, IR, UV, TG and single crystal X-ray diffraction. Compounds 1, 2 and 3 consist of 2-aminopyridine cations together with different POMs, [P₂Mo₅O₂₃]^6-, [V₁₀O₂₈]^6- and [PMo₁₂O ₄₀]^3-, respectively. 2-Aminopyridine cations in 1 orderly link [P₂Mo₅O₂₃]^6- like ribbons via alternating N-H⋯O and C-H⋯O hydrogen bonding interactions and compound 1 exhibits one dimensional empty channel. It is resulted from that the weak interactions between [P₂Mo₅O₂₃] ^6- leave equal sized cavities in which 2-aminopyridine just fits. Whereas the varying distances between POMs in compounds 2 and 3 caused by their different interactions between POMs lead to the disorder of 2-aminopyridine. Heating compounds 1 and 3 at 600°C in air for 2 h yielded nanometer or micrometer-scale MoO₃. Their different morphologies result from the different POMs and molecular arrays in their precursors.