Knowledge Bank

Matrix isolation combined with Fourier transform infrared spectroscopy has been employed to investigate the interconversion of $N2O3$ conformers in an argon matrix under pulsed UV laser irradiation. Irradiation of an argon matrix containing NO and $NO2$ with a 355 nm pulsed laser causes the conversion of asym-$N2O3$ to a new conformer, trans-cis $N2O3$. The vibrational assignment of trans-cis $N2O3$ have been performed for the first time. The observed vibrational frequencies are in good agreement with Density Functional Theory (DFT) calculations at BLYP/6-31$G\ast$ level and {ab initio} calculations at the MP2 level with 6-31$G\ast$ and 6-311$G\ast$ basis sets. Upon annealing the Ar matrix, the thermally induced conversion of trans-cis into sym-$N2O3$ takes place predominantly. Irradiation of asym-$N2O3$ with a 266 nm pulsed laser not only leads to the conversion to trans-cis $N2O3$, but sym-$N2O3$ as well. A mechanism of photo-induced isomerization of the $N2O3$ conformers is proposed.