Synthesis, crystal structure and spectral properties of diammonium dihydrogen N-(methylene-2-pyridine)-N,N,-di-(methylenephosphonate)

In this paper synthesis, crystal structure and spectral properties of a new, N-(methylene-2-pyridine)-N,N,-di-(methylenephosphonic) acid (hereinafter IV) are reported. The X-ray structure analysis revealed that in crystal of the ammonium dihydrogen N-(methylene-2-pyridine)-N,N-di(methylenephosphonate) (hereinafter V) two of the six oxygen atoms from phosphonic groups are protonated and form strong hydrogen bonds, moreover the N(pyridine) and N(amino) atoms are deprotonated. The acid–base properties of studied compound in aqueous solution indicated that the dissociation constants pK1dis 0.70 ± 0.03 and pK2dis 0.98 ± 0.05 are very similar to that determined for nitrilotri(methylphosphonic) acid.

Highlight
► Synthesis, X-ray structural and spectroscopic characterization of N-(methylene-2-pyridine)-N,N,-di(methylenephosphonic) acid are presented.
► Lowest dissociation constants (unavailable with other methods) were determined.