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.

Photo release of nitrous oxide from the hyponitrite ion studied by infrared spectroscopy. Evidence for the generation of a cobalt-N2O complex. Experimental and DFT calculations.

The solid state photolysis of sodium, silver and thallium hyponitrite (M2N2O2, M=Na, Ag, Tl) salts and a binuclear complex of cobalt bridged by hyponitrite ([Co(NH3)5-N(O)-NO-Co(NH3)5]4+) were studied by irradiation with visible and UV light in the electronic absorption region. The UV-visible spectra for free hyponitrite ion and binuclear complex of cobalt were interpreted in terms of Density Functional Theory calculations in order to explain photolysis behavior. The photolysis of each compound depends selectively on the irradiation wavelength. Irradiation with 340-460nm light and with the 488nm laser line generates photolysis only in silver and thallium hyponitrite salts, while 253.7nm light photolyzed all the studied compounds. Infrared spectroscopy was used to follow the photolysis process and to identify the generated products. Remarkably, gaseous N2O was detected after photolysis in the infrared spectra of sodium, silver, and thallium hyponitrite KBr pellets. The spectra for [Co(NH3)5-N(O)-NO-Co(NH3)5]4+ suggest that one cobalt ion remains bonded to N2O from which the generation of a [(NH3)5CoNNO]+3 complex is inferred. Density Functional Theory (DFT) based calculations confirm the stability of this last complex and provide the theoretical data which are used in the interpretation of the electronic spectra of the hyponitrite ion and the cobalt binuclear complex and thus in the elucidation of their photolysis behavior. Carbonate ion is also detected after photolysis in all studied compounds, presumably due to the reaction of atmospheric CO2 with the microcrystal surface reaction products. Kinetic measurements for the photolysis of the binuclear complex suggest a first order law for the intensity decay of the hyponitrite IR bands and for the intensity increase in the N2O generation. Predicted and experimental data are in very good agreement.