Anhydrous MnBr2 was dissolved slowly in molten tetra-n-butylphosphonium bromide, TBP+Br− (Alfa Inorganics) to form a yellowish green solution. Samples of 0.056 mole/liter concentration were prepared in an atmosphere of pure dry nitrogen. Then successive additions of MnBr2 resulted in the corresponding solutions of 0.296, 0.372, 0.396, 0.948, 1.1966, and 2.4067 moles/ liter concentrations. The molten samples were transferred to a quartz cell of path length 1.0 ± 0.0005 cm and the spectra were recorded on a digitalized Cary model 14 spectrophotometer using the furnace as described earlier MnBr2 (2.4067 moles/liter)-rich mixture of TBP+Br− supercooled to a glassy material, the spectra of which were recorded at 25.5, 112, and 158°C using a reduced path length of 0.1 ± 0.0005 cm. The spectrum of the solvent was recorded at 112 and 158°C using the same optical cell and path length.
N. Islam, "Optical Spectra of Manganese (II) Bromide in Molten tetra-n-Butylphosphonium Bromide," Appl. Spectrosc. 29, 266-268 (1975)