Structural characterization and physicochemical features of a new arsenate salt templated by mono and di-protonated 4-aminopyridine cations: (C5H7N2)(C5H8N2)[AsO4]·H2O

Abstract

Single crystals of a new organic–inorganic hybrid compound, with the formula (4-APH)(4-APH2)[AsO4]·H2O, was synthesized at room temperature by slow evaporation method and characterized by X-ray diffraction at 150K, DSC–TG measurements, FT-IR and Raman spectroscopies. The title salt, (C5H7N2)(C5H8N2)[AsO4]·H2O, contains mono and diprotonated 4-aminopyridine cations, an arsenate trianion and one water molecule. The diprotonated 4-ammoniumpyridinium dication [C5H8N2]2+ is disordered over two positions with refined site occupancies of 0.73 and 0.27 however the monoprotonated 4-aminopyridinium cation [C5H7N2]+ is ordered. The 4-aminopyridinium rings are essentially planar and occur in stacks along b axis. In the crystal, the AsIII atom is coordinated by four O atoms in a slightly distorted tetrahedral geometry. The arsenate O atoms link the 4-aminopyridinium cations and water molecules into a three-dimensional network via intermolecular O–H···O and N–H···O hydrogen bonds. Additionally, in this structure, the different types and the nature of aromatic–aromatic interactions can distinguish between a stacked arrangement are parallel displaced and T-shaped conformation. Furthermore, the room temperature IR and Raman spectra of the title compound were recorded and analyzed. On the basis of detailed vibrational studies, the detailed assignment confirms the presence of the organic groups and the anionic entities. Besides, the thermal analysis studies have been performed, but no phase transition was found in the temperature range 298–625K. Results from X-ray crystallography, Raman, IR spectroscopy and thermal analysis are combined to provide a description of the new organic arsenate monohydrate, (C5H7N2)(C5H8N2)[AsO4]·H2O.