New acidic pyrophosphate CoK1.078N0.922(H2P2O7)2.2H2O. Crystal structure and vibrational spectroscopy
The synthesis and single crystal X-ray structure are reported for a new acidic pyrophosphate dihydrate CoK1.078N0.922(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 Ci group symmetry, with the Co cation on the inversion center. The IR spectrum of CoK1.078N0.922(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.
