1393563-92-2Relevant academic research and scientific papers
Nitric oxide dioxygenation reaction by oxy-coboglobin models: In-situ low-temperature FTIR characterization of coordinated peroxynitrite
Kurtikyan, Tigran S.,Eksuzyan, Shahane R.,Hayrapetyan, Vardan A.,Martirosyan, Garik G.,Hovhannisyan, Gohar S.,Goodwin, John A.
, p. 13861 - 13870 (2012/10/08)
The oxy-cobolglobin models of the general formula (NH3)Co(Por) (O2) (Por = meso-tetra-phenyl and meso-tetra-p-tolylporphyrinato dianions) were constructed by sequential low temperature interaction of NH 3 and dioxygen with microporous layers of Co-porphyrins. At cryogenic temperatures small increments of NO were introduced into the cryostat and the following reactions were monitored by the FTIR and UV-visible spectroscopy during slow warming. Upon warming the layers from 80 to 120 K a set of new IR bands grows with correlating intensities along with the consumption of the ν(O2) band. Isotope labeling experiments with 18O 2, 15NO and N18O along with DFT calculations provides a basis for assigning them to the six-coordinate peroxynitrite complexes (NH3)Co(Por)(OONO). Over the course of warming the layers from 140 to 170 K these complexes decompose and there are spectral features suggesting the formation of nitrogen dioxide NO2. Upon keeping the layers at 180-210 K the bands of NO2 gradually decrease in intensity and the set of new bands grows in the range of 1480, 1270, and 980 cm -1. These bands have their isotopic counterparts when 15NO, 18O2 and N18O are used in the experiments and certainly belong to the 6-coordinate nitrato complexes (NH 3)Co(Por)(η1-ONO2) demonstrating the ability of oxy coboglobin models to promote the nitric oxide dioxygenation (NOD) reaction similar to oxy-hemes. As in the case of Hb, Mb and model iron-porphyrins, the six-coordinate nitrato complexes are not stable at room temperature and dissociate to give nitrate anion and oxidized cationic complex Co(III)(Por)(NH3)1,2.
