Infrared spectra and frequency assignment of two isomers of nitrobenzene, namely the phenyl nitrite C6H5-ONO molecule and the phenoxyl radical-nitric oxide complex C6H5O-NO, in solid argon are presented. The phenoxyl radical-nitric oxide complex was produced through UV light irradiation of nitrobenzene in low-temperature solid argon matrix. The complex rearranged to the more stable phenyl nitrite molecule on sample annealing. The aforementioned species were identified on the basis of isotopic IR studies with (C6H5NO2)-N-15 and C6D5NO2, as well as density functional theory calculations.