Infrared and Raman spectra and normal coordinate analysis of zirconium diphosphate

Vibrational spectra study of Mo(V) phosphates as examples of different geometries of dimolybdenyl species

“…According to these data, we can assign the weak shoulders in the Raman patterns near 960 cm 21 and at 930 cm 21 to the Raman active components of the n as (POP) and n as (MoLO) modes. The relative intensities of the observed maxima agree with these assignments.…”

“…By contrast, the MoLO stretching modes are generally strong and sharp both in IR and in Raman. These considerations allow us to confidently assign the strong Raman peak at 948 cm 21 to the totally symmetric stretching mode of molybdenyl groups. This position agrees with that of the MoLO stretch in the Raman spectrum of a-KMoO(P 2 O 7 ), i.e.…”

“…According to Table 1 we expect here 5 IR active modes and 6 Raman active modes, one only of which belongs to the A g symmetry. The IR and Raman spectra of different metal diphosphates 19,23 show that the n as (POP) modes on pyro-and poly-phosphates are responsible for strong and rather broad IR bands centred in the range 970-940 cm 21 , while the corresponding Raman-active modes are weak and become even inactive when the P-O-P bridges are linear. By contrast, the MoLO stretching modes are generally strong and sharp both in IR and in Raman.…”

“…947 cm 21 . 24 In the IR spectrum we can suppose that the overall absorption in this region (centred near 950 cm 21 ) is due to the IR active n as (POP) modes, while the two sharp maxima at 936 cm 21 and 928 cm 21 are associated to the IR active n s (MoLO) (B 2u ) and n as (MoLO) (B 1u , B 3u ) modes.…”

“…The FT-Raman spectra were recorded using a Brucker FTS100 (Nd-YAG laser). The skeletal spectra in the region above 400 cm 21 were recorded with KBr pressed disks and with a KBr beam splitter, while those in the far infrared region (400-50 cm 21 ) were recorded using powder deposited on polyethylene disks, and with a ''solid substrate'' beam splitter. As determined previously by Guesdon et al in their XRD study on single crystals and powders, 11,16 See http://www.rsc.org/suppdata/ jm/b0/b007416k/ coordinated diphosphate groups, two bridging oxygen atoms with the nearer Mo octahedron and one free corner or, more precisely, one short MoLO ''molybdenyl'' bond (1.697 A ˚).…”