Crystal engineering and structural diversity of 2-aminopyridinium hypodiphosphates obtained by crystallization and dehydration

Abstract

Organic-inorganic salts and ionic co-crystals of hypodiphosphoric acid (H4P2O6) with 2-aminopyridne (2ap) have been synthesized and characterized by X-ray crystallography, thermogravimetry, element analysis and Fourier-transform infared spectroscopy. (2apH)4(H3P2O6)2(H2P2O6)∙2H2O (1), (2apH)2(H2P2O6)∙2H2O...

Structural variety and dehydration in 3-aminopyridine–hypodiphosphoric acid–water system

“…among all 2- and 3-aminopyridinium hypodiphosphates. 31 The 3-aminopyridinium cation in ( 5 ) forms eight hydrogen bonds with five different dianions giving rise two different eight-membered rings – R 2 2 (8) – and a rarely observed structural motif, six-membered ring – R 2 2 (6) (Fig. S12 in the ESI†).…”

“…Up to now, only few examples of structural studies of organic hypodiphosphates are known, which are 2-aminopyridiunium salts and co-crystals, 31 tetraalkylammonium ionic co-crystals, 32 imidazolium 33 and adeninium 34 salts. Worth mentioning is the dehydration in tetrabutylammonium salt crystal, which took place as single-crystal-to-single-crystal process and resulted in conformational transformation of the H 3 P 2 O 6 − anion from staggered to perfectly eclipsed form.…”

“…In our recent paper, a structural study of a series of salts and co-crystals in 2-aminopyridine–hypodiphosphoric acid–water (2ap–PP–H 2 O) system was presented, and the dehydration process was shown to be the way to obtain new structural motifs and otherwise inaccessible anhydrous crystalline forms. 31 Dehydrations were destructive to the crystals. These studies showed that characteristic hypodiphosphate structural motifs depended on the ionization state of the PP anions, and that 2-aminopyridine–hypodiphosphate contacts were dominated by N–H⋯O hydrogen bonds, which gave rise to the main supramolecular heterosyntons with R 2 2 (8) or R 2 2 (9) ring formation (Fig.…”

“…1). 31 With this in mind, we decided to extend the scope of our research to 3-aminopyridinium hydpodiphosphates, hoping to find an answer to the question about the influence of the NH 2 group position on the PP-PP and PP-ap interactions, the structural motifs created, and the dehydration of the crystals formed. This work continues exploration of the supramolecular chemistry, thermal stability and spectroscopic characterization of hypodiphosphates.…”

“…This work continues exploration of the supramolecular chemistry, thermal stability and spectroscopic characterization of hypodiphosphates. [31][32][33][34] A series of 3-aminopyridine-containing compounds is presented (Scheme 1). Two of the hybrid crystals: (1) and ( 3) contain water molecules.…”