Infrared, Raman and resonance Raman spectra and lattice dynamics calculations of the solid potassium(I) palladium(II) thiophosphate compound KPdPS4

The UV-Visible (350-900 nm), infrared and Raman (30-800 cm(-1)) spectra of a new transition metal thiophosphate solid compound, KPdPS4, were analyzed using powder samples and single-crystal platelets. From polarized absorbanc e measurements, the main electronic transitions of the F-1(2) <-- (1)A(1) t ype due to the (PS4)(3-) groups are localized in the 400-520 nm range and a ll the expected infrared vibrational modes were observed in the 600-30 cm(- 1) region; various polarized Raman measurements were also performed. The vi brational assignments were then checked by complete valence force field lat tice dynamics calculations in the different symmetry blocks of the tetragon al crystal structure (D-4h(14)). Potential energy distributions and mean sq uared vibrational amplitude calculations revealed strong v(Pd-S) and delta( S-P-S) couplings in the one-dimensional inorganic polymer anionic 1(infinit y)[PdPS4](-) chains and remarkably high v(Pd-S) stretching modes near 350 c m(-1.) Compared with results for the analogous Ni(II) compound, there was a significant increase in the M-S force constants, varying from 75 Nm(-1) (N i-S) to 90 Nm(-1) (Pd-S) in accordance,vith the Pauling electronegativity s cale. Furthermore, various resonance Raman spectra of micrometer-sized samp les were recorded using a confocal microscope instrument in order to charac terize not only the existence of chains having a distribution of length but also some Raman impurity bands coming from the dithiophosphate compound, K 4Pd(PS4)(2). Also, resonance Raman spectra of powder samples were recorded using several exciting radiation wavelengths over the range 800-500 nm in o rder to probe the nature of the low-energy electronic transition at 658 nm; the Raman excitation profiles of several fundamentals were thus establishe d and they demonstrate that both totally symmetric and non-totally symmetri c stretching and bending modes of the PS4 and PdS4 groups are markedly enha nced. We therefore conclude that several ligand to metal charge-transfer el ectronic transitions are overlapped and involved in vibronic coupling mecha nisms,vith higher energy bands. Finally, a comparison of the induced Raman scattering processes in the Cu3PS4, KNiPS4 and KPdPS4 solid compounds showe d that the ligand to metal charge transfers and the crystal field effects h ave a strong influence on the optical and vibronic properties of these thio phosphate compounds, Copyright (C) 1999 John Wily & Sons, Ltd.