The crystal structures of iron and cobalt pyridine (py)–sulfates, [Fe(SO<sub>4</sub>)(py)<sub>4</sub>]<sub> <i>n</i> </sub> and [Co<sub>3</sub>(SO<sub>4</sub>)<sub>3</sub>(py)<sub>11</sub>]<sub> <i>n</i> </sub>
Acta crystallographica. Section E, Crystallographic communications