Exploring the electronic structure of [RuF₅NO]^2- ion by the generation of a metastable state (MS1)

Some mononitrosyl complexes of transition metals exhibit one or two metastable states (linkage isomers, MS1 and MS2) when irradiated at low temperatures with appropriate wavelengths. In this work, the generation of metastable state one (MS1) (or Ru-ON linkage isomer) in K₂[RuF₅NO].H₂O at 77 K was studied by sample excitation using laser light in a wide range of wavelengths. The effects of irradiation was monitored by infrared spectroscopy. ν(NO) in the ground state was shifted by -161 cm^-1 when the complex was excited to MS1, a magnitude similar to that observed in other transition metal nitrosyls for a such state. We report on the excitation and deactivation of metastable states by using a wide variety of laser lines. A novel method for exploring the electronic structure of [RuF₅NO]^2- through the generation of MS1 is proposed. For this purpose, a sample was carefully irradiated with the same intensity of light for all laser lines in the spectral region 260-1064 nm. The integrated area under the ν(NO)_MS1 band was used as a measure of MS1 population. The profile peaks of the MS1 population (ν(NO)_MS1 band area) vs. the irradiation wavelength fit well with those of the electronic spectrum of the [RuF₅NO]^2- ion in an aqueous solution. The onset temperature for MS1 decay in K₂[RuF₅NO].H₂O, at approximately 180 K, is slightly lower than the average reported for other ruthenium-nitrosyl systems.