Fourier-transform spectra of metal salts of phytic acid in the mid- to far-infrared spectral range

Phytic acid (myo-inositol 1,2,3,4,5,6-hexakisphosphate; IP6) is the storage substance for phosphorus and many metals in plant seeds. Based on Synchrotron-based Fourier-transform infrared (FT-IR) spectra in the mid-infrared range from 1300 to 700 cm−1, nine synthesized metal-IP6 salts, with monovalent to trivalent coordination, were classified into four groups: trivalent metal-IP6 salts, second-group divalent metal-IP6 salts, d-block and p-block divalent metal-IP6 salts, and monovalent metal-IP6 salts. Synchrotron FT-IR analysis in the far-infrared range, from 650 to 100 cm−1, contained clear, broad bands specific to each metal-IP6 salt, including monovalent and divalent metal-IP6 salts. These broad bands are likely derived from vibrations of bonds between the metal and the oxygen of IP6. These unique far-infrared spectra may provide useful information for identifying metal-IP6 salts in biochemical fine-image analyses of seed tissues using synchrotron-based FT-IR microspectroscopy.