Infrared, Raman and resonance Raman spectra of the solid nickel(II) thiophosphate compound (PPh4)3 [(NiPS4)3] and force constants in the trinickel [Ni3P3S12]3− cyclic anion
✍ Scribed by C. Sourisseau; V. Rodriguez; S. Jobic; R. Brec
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 184 KB
- Volume
- 30
- Category
- Article
- ISSN
- 0377-0486
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✦ Synopsis
The UV-visible (350-900 nm), infrared and Raman (30-800 cm -1 ) spectra of a new transition metal thiophosphate solid compound, (PPh 4 ) 3 [(NiPS 4 ) 3 ], were analyzed using powder samples. Electronic transitions of the 1 F 2 →
1
A 1 type originating in the (PS 4 ) 3-groups were detected from visible absorbance measurements in the 440-520 nm range and most of the expected infrared and Raman vibrational modes of the trimetallic ring anion [Ni 3 P 3 S 12 ] 3-were observed in the 600-30 cm -1 region. Also, resonance Raman spectra were recorded using exciting radiation of several wavelengths in the 680-450 nm range and the Raman excitation profiles of several fundamentals were established: they all peak near 488 nm and exhibit the strongest enhancements for totally symmetric and non-totally symmetric stretching and bending modes of (NiS 4 ) groups. It is therefore concluded that several ligand to metal charge-transfer electronic transitions are overlapped and involved in vibronic coupling mechanisms. Furthermore, the vibrational assignments were checked by a valence force field calculation for an isolated [Ni 3 P 3 S 12 ] 3-anion of C 3v symmetry. The potential energy distributions and mean squared vibrational amplitudes revealed strong n(Ni-S) and d(S-P-S) couplings and relatively high n(Ni-S) stretching modes at near 310 cm -1 . Compared with results in the one-dimensional KNiPS 4 compound containing infinite anionic chains 1 1 [NiPS 4 ] -, one notes a force constant increase on the P-S exocyclic (m 1 ) bonds, no change on the bridged (m 2 and m 3 ) P-S bonds and a slight increase in the Ni-S stretching force constants varying from 75 to 85 N m -1 in accordance with a localized ligand to metal charge-transfer mechanism. Hence a comparison of the induced Raman scattering processes in the (PPh 4 ) 3 [(NiPS 4 ) 3 ] and KNiPS 4 solid compounds shows that the ligand to metal charge transfers and the crystal field effects have a strong influence on the vibrational properties in these thiophosphate compounds.