Vibrational Study of the Methyl Viologen Dication MV(2+) and Radical Cation MV.(1+) in SEveral Salts and as an Intercalate in Some Layered MPS3 Compounds

Article abstract of DOI:10.1039/f19848003257

Infrared and Raman spectra (1800-200 cm^-1) of methyl viologen (1,1'-dimethyl-4,4'-bipyridyl dication or MV(2+)) (<1H8> and <2H8> derivatives) have been recorded for the chloride, iodide and palladate salts and for the intercalated compounds of formula M0.84PS3-(MV)0.16 (with M = Mn and Cd), FePS3-(MV)0.15 and Zn0.71PS3-(MV)0.29.Complete assignments have been proposed for all these species.The methyl viologen appears to be intercalcated in its dicationic form and is weakly interacting with the host lattice.In the ZnPS2 system the MV(2+) pyridyl rings are twisted while in MnPS3, CdPS3 and FePS3 the cation rings are coplanar and parallel to the sulphur layers.From these results, a model of packing of MV(2+) in the MPS3 host lattices has been established which accounts for the different interaction rates.Finally, the reduced product, MV^.(1+), has been studied in both the chloride salt and the CdPS3 interaction compound: in the latter case the radical cation behaves as though diluted and trapped inside an inert matrix, demonstrating unexpected stability.