Synthesis of water-soluble zinc(ii) nitrilotris(methylenephosphonate). Molecular structure of bis(4-carboxyphenylaminium) nitrilotris(methylenephosphonate) dihydrate

Nitrilotris(methylenephosphonic)acid N[CH2P(O)(OH)2]3 (H6L) reacts with zinc oxide in an aqueous medium to give a poorly soluble polymeric crystalline salt (ZnH4L)n. The reaction proceeds through the intermediate formation of a soluble monomer complex ZnH4L. The water-soluble amorphous forms of the coordination compound used as microfertilizers were obtained by treatment of a suspension of this salt with 2-aminoethanol, 2-amino-2-(hydroxymethyl)propane-1,3-diol, 2,2′-(ethylenedioxy)bis(ethylamine). p-Aminobenzoic acid H2NC6H4COOH reacts in an aqueous solution with hexabasic nitrilotrimethylenephosphonic acid, as well as with the monomeric complex ZnH4L, giving crystals of bis(4-carboxyphenylaminium) nitrilotris(methylenephosphonate) dihydrate H4L2− · 2(H3N-C6H4-COOH)+ · 2H2O. The compounds were investigated by elemental analysis, IR and UV spectroscopy, X-ray phase analysis and X-ray diffraction analysis. Tests of the water-soluble complex with 2-aminoethanol ZnHL3− · 3(H3NCH2CH2OH)+ · 2H2O in the laboratory experiment with seeds of two agricultural crops showed a positive agronomic effect.