posted on 2022-03-23, 21:30authored byJingfang Zhou, Rukang Li
A proton-rich POM-type molybdenum
phosphate K12Mo8O20(HPO4)8(PO4)Cl was successfully obtained. It crystallizes
in a noncentrosymmetric
tetragonal space group of P–4 (No. 81) with
the unit cell parameters of a = 9.6580(4) Å, c = 14.2607(10) Å, and Z = 1. The
occurrence and positions of the light element H in the structure are
inferred from single-crystal X-ray diffraction and confirmed by DFT
calculations. The hydrogen atoms are found to form hydroxyl bonds
with O atoms from P(2)O4 and P(3)O4 constituting
the [Mo4P4O26H4]4– layers but are only weakly bound to the isolated P(3)O4 group through hydrogen bonds. The title compound presents a POM-type
framework of corrugated [Mo4P4O26H4]4– layers with four K+ ions and mixed ions (K4Cl3+ and isolated PO43–) orderly imbedding in the interlayer
spaces with distances of 5.0396 (1) and 5.5966 (3) Å, respectively.
The proton-rich nature and the structure feature were further verified
by a series of experiments including 1H, 7Li,
and 31P MAS NMR spectra, IR spectroscopy, and thermal analysis.
Moreover, the weak bonding and large interlayer spaces make K+ and H+ ions susceptible to exchange with ions
of Cs+, Ba2+, Zn2+, Pb2+, Cu2+, and Ni2+ commonly presented in chemical
pollutants or nuclear wastes. In addition, the title compound shows
a small second-harmonic generation signal, consistent with its noncentrosymmetric
structure.