A combined crystal-structural,IR,Raman and 31P NMR spectroscopy of a new iron phosphate FePb2(P2O7)(PO4)

Fepb2(p2o7)(po4) has been synthesized using fe(no3)3.9h2o,pb(no3)2 and nh4h2po4 as starting materials. single crystals were grown by a long annealing (4 days) at 900°c in open air. fepb2(p2o7)(po4) crystallizes in the monoclinic space group p21/c,with a=6.484(1) å,b=7.116(1) å,c=19.531(1) å,β=99.31(1)°,and z=2. the fepb2(p2o7)(po4) structure can be described as a three-dimensional array containing isolated [fe3+o6] octahedra connected through po4tetrahedra and p2o7 groups,enclosing a network of cavities where the lead cations reside. ir and raman characterization of new phosphate fepb2(p2o7)(po4) revealed the existence of isolated po4 3- and p2o7 4- groups from each others,and feo6 and pbon groups in which the fe-o and pb-o bonds are of lower intensity than that of p-o. by comparing the frequencies values between ir and raman spectrums of fepb2(p2o7)(po4),we can conclude that the correlation effect is more important than the site effect. the analysis of the 31p nmr spectrum in the solid state of phosphate fepb2(p2o7)(po4) confirms the presence of po4 3- and p2o7 4- groups in agreement with the results determined by crystallography,ir and raman. the study by mössbauer spectroscopy allowed us to characterize the degree of oxidation of the iron,its environment in the structure and in particular the covalent fe-o bonds. © 2017,university of mohammed premier oujda morocco.