New acidic pyrophosphate CoK_1.078N_0.922(H₂P₂O₇)₂.2H₂O. Crystal structure and vibrational spectroscopy

Abstract

The synthesis and single crystal X-ray structure are reported for a new acidic pyrophosphate dihydrate CoK_1.078N_0.922(H₂P₂O₇)₂.2H₂O. The results revealed cobalt (Co) octahedrally coordinated by two water molecules and four oxygen atoms belonging to two (H₂P₂O₇) diphosphate groups. Potassium (K) and nitrogen (N) cations are involved in a complex coordination within resulting cavities from phosphorus tetrahedra and cobalt octahedra. The present compound can be described as a three-dimensional framework made from vertex-sharing polyhedra. The basic unit is the [Co(H₂P₂O₇)₂.2H₂O] moiety, which displays a C_i group symmetry, with the Co cation on the inversion center. The IR spectrum of CoK_1.078N_0.922(H₂P₂O₇)₂.2H₂O confirms the existence of the characteristic bands of acidic pyrophosphate group (H₂P₂O₇), respectively, at 1350–700 cm⁻¹ and 600–400 cm⁻¹ areas and reveals also the characteristic bands of water molecules vibration between the two spectral ranges 4000–1350 cm⁻¹ and 700–600 cm⁻¹. IR spectrum confirms also a bent configuration of the POP bridge.

Graphical Abstract

Keywords:

• New acidic pyrophosphate
• SEM-EDS analysis
• crystal structure
• vibrational spectroscopy
• factor group analysis
• infrared spectrum

Acknowledgments

In this work, the crystal structure was determined by Tereza Vaclavu, Institute of Physics of the Czech Academy of Sciences.

Disclosure statement

No potential conflict of interest was reported by the authors.