Structure and Vibrational Spectra of a New Acidic Diphosphate K₂Cu(H₂P₂O₇)₂·2H₂O

Abstract

Crystals of the acidic diphosphate K2Cu(H2P2O7)2 · 2 H2O, dipotassium copper bis(dihydrogendiphosphate) dihydrate, obtained via two different syntheses, revealed by means of single-crystal X-ray diffraction to be polymorph within triclinic Pī (a = 6.8560(4), b = 7.3140(3), c = 7.5570(4) Å; α = 81.028(4)°, β = 72.327(5)°, γ = 83.697(5)°, V = 355.86(3)Å3) and orthorhombic Pnma (a = 9.8990(6), b = 10.7810(7), c = 13.4010(7) Å, α = β = γ = 90°, V = 1430.17(15) Å3) space groups. Both phases were analyzed by FT-IR and micro-Raman vibrational spectroscopy and interpreted using factor group analysis. No coincidences of majority of the Raman and infrared spectral bands of K2Cu(H2P2O7)2 · 2 H2O confirmed the centrosymmetric structure of these two materials. The vibrational spectra point to a bent POP bridge angle.

GRAPHICAL ABSTRACT

Keywords:

• Acidic
• diphosphates
• crystal structure
• FTIR
• Raman
• copper

Acknowledgments

We thank Mr. G. Chita (Institute of Crystallography-CNR, Bari, Italy) for X-ray data collection.