Amino-Functionalized Layered Crystalline Zirconium Phosphonates: Synthesis, Crystal Structure, and Spectroscopic Characterization

Two new layered zirconium
phosphonates functionalized with amino groups were synthesized starting
from aminomethylphosphonic acid in the presence of different mineralizers,
and their structures were solved from powder X-ray diffraction data.
Their topologies are unprecedented in zirconium phosphonate chemistry:
the first, of formula ZrH­[F3(O3P­CH2NH2)], prepared in the presence of hydrofluoric
acid, features uncommon ZrO2F4 units and a remarkable
thermal stability; the second, of formula Zr2H2[(C2O4)3­(O3PCH2NH2)2]·2H2O, prepared
in the presence of oxalic acid, is based on ZrO7 units
with oxalate anions coordinated to the metal atom, which were never
observed before in any zirconium phosphonate. In addition, the structure
of another compound based on (2-aminoethyl)­phosphonic acid is reported,
which was the object of a previously published study. This compound
has layered α-type structure with −NH3+ groups located in the interlayer space. All of the reported
compounds were further characterized by means of vibrational spectroscopy,
which provided important information on fine structural details that
cannot be deduced from the powder X-ray diffraction data.