Synthesis, structural characterization, IR- and Raman spectroscopy, magnetic properties of new organically templated metal sulfates with 4-aminopyridinium

• A series of twelve 4-aminopyridinium templated metal sulfates were synthesized.
• The compound with Al undergoes a reversible order-disorder phase transition.
• Templating role of organic cation is governed by H-bonds and π-π interactions.
• Selected compounds were characterized by IR, Raman and magnetic studies.

Crystal structures of the series of twelve 4-aminopyridinium templated metal sulfates: (C5H7N2)2[MeII(H2O)6](SO4)2 (MeII = Cu (1), Co (2), Mg (3), Zn (4), Fe (5), Mn (6a)), (C5H7N2)2[MeII(H2O)4(SO4)2]·4H2O (MeII = Mn (6b), Cd (7a)), (C5H7N2)2[MnII(H2O)4(SO4)2] (6c), (C5H7N2)2[Cd(H2O)4(SO4)2] (7b), (C5H7N2)[Al(H2O)6](SO4)2·4H2O (low (8lt) and room temperature (8rt) phases) and (C5H7N2)[FeIII(H2O)4(SO4)2] (9) were determined by single-crystal X-ray diffraction. Compounds 1-6a are isostructural, crystal structure consists of [Me(H2O)6]2+ octahedra, 4-aminopyridinium cations (4ap) and sulfate anions. Crystal packing in 1-6a series is characterized by alternating 4ap and inorganic layers. In the structure of 1 Cu2+ coordination environment is axially deformed due to Jahn-Teller effect to tetragonal bipyramidal. Compounds 6 (a, b) and 7a at ambient conditions dehydrate to produce isostructural complexes 6c and 7b, respectively. In structures of 6c, 7b and 9 sulfate anions are involved in slightly distorted octahedral metal coordination composed of six O atoms from four water molecules and two sulfate anions. Room temperature phase of 8 is characterized by disorder of 4ap around center of inversion. Continuous phase transition at ≈185 K leads to the cell doubling and ordering of 4ap. All of the structures are governed by an extensive three-dimensional hydrogen bond networks, as well as π–π interactions visualized by Hirshfeld surface analysis. Moreover, selected compounds were characterized by the IR and Raman spectroscopy and magnetic measurement studies.

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