Spectroscopic properties and magnetic behavior of [Cr(urea)₆][Cr₂O₇]Br·H₂O

The spectroscopic and magnetic studies of [Cr(urea)₆][Cr₂O₇]Br.H₂O was conducted by using UV- visible and IR spectroscopy and by measuring magnetic susceptibility. Before the spectra were recorded, the complex was purified from aqueous solution by recrystallization. Diffuse reflectance electronic spectra were measured on a JASCO V-570 UV/VIS/NIR spectrophotometer, equipped with an integrating sphere in the range of 200-1500 nm. Diamagnetic correction was applied with Pascal's method. The FT-IR spectrum showed a very strong sharp absorption band at 3634 cm^-1 due to the O-H stretching mode of the hydrate water molecule. The symmetric and asymmetric modes of the noncoordinated NH2 group appeared at 3450 and 3352 cm^-1, respectively, along with an additional less intense band at 3218 cm^-1. The absorption band observed near 1507 cm^-1 is assigned to CO + CN vibrations. This indicates the formation of a CrA-OA(urea) bond instead of the CrA-NA bond.