Structure, Spectra and Photochemistry of 2-Amino-4-Methylthiazole: FTIR Matrix Isolation and Theoretical Studies

Abstract

The structure, tautomerization pathways, vibrational spectra, and photochemistry of 2-amino-4-methylthiazole (AMT) molecule were studied by matrix isolation FTIR spectroscopy and DFT calculations undertaken at the B3LYP/6-311++G(3df,3pd) level of theory. The most stable tautomer with the five-membered ring stabilized by two double C=C and C=N bonds, was detected in argon matrices after deposition. When the AMT/Ar matrices were exposed to 265 nm selective irradiation, three main photoproducts, N-(1-sulfanylprop-1-en-2-yl)carbodiimide (fp1), N-(1-thioxopropan-2-yl)carbodiimide (fp2) and N-(2-methylthiiran-2-yl)carbodiimide (fp3), were photoproduced by a cleavage of the CS–CN bond together with hydrogen atom migration. The minor photoreaction caused by the cleavage of the CS–CC bond and followed by hydrogen migration formed 2-methyl-1H-azirene-1-carbimidothioic acid (fp15). We have also found that cleavage of the CS–CN bond followed by disruption of the N–C bond produced cyanamide (fp11) and the ˙C(CH3)=CH–S˙ biradical that transformed into 2-methylthiirene (fp12) and further photoreactions produced 1-propyne-1-thiole (fp13) or methylthioketene (fp14). Cleavage of the CS–CC bond followed by disruption of the N–C bond produced propyne (fp22) and the ˙S–C(NH2)=N˙ biradical that transformed into 3-aminethiazirene (fp23); further photoreactions produced N-sulfanylcarbodiimide (fp25). As a result of these transformations, several molecular complexes were identified as photoproducts besides new molecules in the AMT photolysis process.

Asymmetric Ligands of a Metal–Organic Framework on Enhanced Photocatalytic CO2 Reduction

“…In situ DRIFTS was used to detect intermediates to reveal the mechanism (Figure c). Peaks at 1050 and 1200 cm –1 were symmetric vibrations of N–C, the peak at 1680 cm –1 was the symmetric vibration of CO, and the N–CO–O intermediate formed by adsorbed CO 2 on N (B-pyrazole), consistent with the DFT results. In addition, the peaks at 1150, 1400, and 1640 cm –1 attributed to the in-plane bending vibration of N–H and symmetric vibrations of C–N and CO, respectively, which was considered to be NH–CO species gradually generating in the reaction.…”