Three
new zinc phosphites, [HIm]2[Zn3(HPO3)4] (1), [Zn2(HPO3)2Im2] (2), and [Zn(HPO3)Im]
(3) (Im = imidazole), have been synthesized from
the hydro/solvothermal reaction of zinc acetate, dimethyl phosphite,
and imidazole by varying the temperature and solvent of the reaction
medium. The structure of 1 is built from vertex-sharing
of four HPO3-capped Zn3P3 units and
adopts an open framework with 12-ring channels stabilized by HIm cations
via N–H···O hydrogen bonds. For 2, the inorganic skeleton is comprised of alternating ZnO4 and HPO3 tetrahedra, while the coordinatively associated
ZnN2O2 fragments occupy the 12-ring hexagonal
channels. Compound 3 adopts a ladder-type one-dimensional
structure and exhibits N–H···O hydrogen-bonding
interactions to afford a supramolecular assembly. A plausible rationale
on the genesis of 1–3 has been put
forth by reacting the preformed inorganic zinc phosphites Zn{OP(O)(OMe)H}2 or [Zn2(HPO3)2(H2O)4]·H2O with imidazole as the structure-directing
ligand. Alternating-current impedance measurements reveal that 1 and 3 exhibit proton conductivities on the
order of 10–3–10–4 S cm–1 between 25 and 100 °C under 35 and 77% relative
humidity in repeated impedance cycles (E
a = 0.22–0.35 eV). On the contrary, the conduction property
is completely impaired in 2 under similar conditions.