Structural and vibrational characteristics of amphiphilic phosphonate salts

1-Decylphosphonic acid (1), ammonium 1-decylphosphonate (NH4C10H21PO3H) (2), ethylenediaminium 1-decylphosphonate 1,5 hydrate (enH2C10H21PO3·1.5H2O) (3) and calcium 1-decylphosphonate (Ca(C10H21PO3H)2) (4) were prepared and characterized by IR and Raman spectroscopy. The structures of 2 and 3 were determined by single crystal X-ray diffraction analysis. Compound 2 crystallizes in the P 1 ¯ space group of triclinic system with two molecules in the asymmetric unit cell whereas compound 3 crystallizes in C2/c space group of monoclinic system with four molecules in the unit cell and both exhibit layered supramolecular structures generated by ionic interaction, H-bonding and alkyl chain interdigitation in the case of 3. The FT-IR and Raman spectra have been assigned in the range 4000–500 cm−1 for all compounds, and reveal the trans conformation of alkane chain in all compounds.