Synthesis, Crystal Structure, and Proton Conductivity of One-Dimensional, Two-Dimensional, and Three-Dimensional Zirconium Phosphonates Based on Glyphosate and Glyphosine

The
reaction of two small phosphono-amino acids based on glycine
(glyphosine and glyphosate) with zirconium under mild conditions led
to the attainment of three related zirconium derivatives with 1D,
2D, and 3D structures of formulas ZrF­[H3(O3PCH2NHCH2COO)2] (1), Zr3H8[(O3PCH2)2NCH2COO]4·2H2O (2), and
Zr­[(O3PCH2)­(HO3PCH2)­NHCH2COOH]2·2H2O (3), respectively,
whose structures were solved by X-ray powder and single-crystal diffraction
data. The glyphosate derivative has 1D ribbon-type structure whereas
the dimensionality of the glyphosine-derived materials (2D and 3D)
can be tuned by changing the synthesis conditions. The low-dimensional
compounds (1 and 2) can be directly produced
in the form of nanoparticles with different size and morphology whereas
the 3D compound (3) has a higher crystallinity and can
be obtained as single crystals with a prismatic shape. The different
structural dimensionality reflects the shape and size of the crystals
and also differently affects the proton conductivity properties, measured
over a wide range of temperature at 95% relative humidity. Their high
thermal and chemical stability together with the small size may promote
their use as fillers for polymeric electrolyte membranes for fuel
cells applications.