Synthesis, crystal structure, and vibrational spectroscopic and UV–visible studies of Cs2MnP2O7

A new member of the A2MP2O7 diphosphate family, Cs2MnP2O7, has been synthesized and structurally characterized. The crystal structure was determined by single crystal X-Ray diffraction. Cs2MnP2O7 crystallizes in the orthorhombic system, space group Pnma (♯62), with the unit cell parameters a=16.3398(3), b=5.3872(1), c=9.8872(2) Å, Z=4 and V=870.33(3) Å3. The structure parameters were refined to a final R1/wR2=0.0194/0.0441 for 1650 observed reflections. The 2D framework of Cs2MnP2O7 structure consists of P2O7 and MnO5 units. The corner-shared MnO5 and P2O7 units are alternately arranged along the b axis to form [(MnO)P2O7]∞ chains. These chains are interconnected by an oxygen atom to form sheets parallel to the (b, c) plane. The cesium atoms are located between the sheets in 9- and 10-fold coordinated sites. The infrared and Raman vibrational spectra have been investigated. A factor group analysis leads to the determination of internal modes of (P2O7) groups. UV–visible spectrum consists of weak bands, between 340 and 700 nm, assigned to the forbidden d–d transitions of Mn2+ ion, and of a strong band around 250 nm, attributed to the OMn charge transfer.