Photochemical transformations of 5-methyltetrazole. Matrix isolation FTIR and DFT studies

• Two tautomers of 5-methyltetrazole (MT) isolated in argon matrices.
• Photochemical reactions of MT were induced by tunable UV laser radiation.
• Products of the ring cleavage differ in their behavior during irradiation.
• Further photoreactions of methylcarbodiimide leading to HCN, HNC and their dimers.

In situ photolysis of 5-methyltetrazole (MT) isolated in low temperature argon matrices was induced by tunable UV laser radiation. The progress of the reactions was followed by FTIR spectroscopy that allowed for spectroscopic identification of three photoproducts resulting from the MT ring cleavage, namely C-methylnitrilimine CH3CNNH, N-methylcarbodiimide CH3NCNH, methylcyanamide CH3NHCN. The kinetic profiles obtained for these products show different behavior of the species in the course of irradiation. The N-methylcarbodiimide molecules were found to decompose further into two HCN or HNC molecules that interact in the matrix cages to form different hydrogen bonded dimers. Interpretation of the observed photoprocesses was supported by quantum chemical calculations (DFT, TD-DFT).

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