Knowledge Bank

Matrix isolation infrared spectroscopy was used to characterize the complexes of H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$Si and HSi with N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ that result from the vacuum-ultraviolet photolysis of silane (SiH$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}$) in cryogenic nitrogen (N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$) matrices. Experiments were performed by depositing mixtures of SiH$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}$ with N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ onto a CsI window at 12 K while simultaneously photolyzing the mixture with 121 nm vacuum-ultraviolet radiation from a hydrogen resonance lamp. The infrared bands of the H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$SiN$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ complex observed in these experiments are the N-N stretching mode at 2274.2 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ and the H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$Si asymmetric and symmetric stretching modes at 2013.6 and 2009.4 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$, respectively. The infrared bands of the HSiN$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ complex observed in these experiments are the N-N stretching mode at 2023.9 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$, the Si-H stretching mode at 2006.6 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$, and the H-Si-N bending mode at 813.7 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. The assignment of these bands to the H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$SiN$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ and HSiN$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ complexes is established by performing experiments with isotopic reagents (SiD$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}$, $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$), by performing matrix annealing experiments (warming to 20 - 30 K and refreezing to 12 K), by performing mercury-xenon lamp matrix photolysis experiments, and by comparison to density functional theory calculations at the B3LYP/aug-cc-pVTZ level.