Structural investigation of nitrogen-linked saccharinate–tetrazole

The molecular structure of nitrogen-linked saccharinate–tetrazole, N-(1,1-dioxo-1,2-benzisothiazol-3-yl)-amine-1H-tetrazole (BAT), was investigated in the crystalline state using X-ray crystallography and infrared and Raman spectroscopies, and isolated in argon matrix by infrared spectroscopy. Interpretation of the experimental results was supported by quantum chemical calculations undertaken at the DFT(B3LYP)/6-311++G(3df,3pd) level of theory. In the neat crystalline solid (space group C2/c, a = 21.7493(3) Å, b = 8.85940(10) Å, c = 10.76900(10) Å, β = 103.3300(10) deg; Z = 8), BAT units exist in the (1H)-tetrazole aminosaccharin tautomeric form, with the NH spacer establishing a hydrogen bond to the nitrogen in position-4 of the tetrazole group of a neighbour molecule, and the NH group of the tetrazole fragment forming a bifurcated H-bond to the saccharyl nitrogen of the same molecule and to one of the oxygen atoms of a second neighbour molecule. On the other hand, according to both the matrix isolation infrared studies and the theoretical calculations, the isolated BAT molecule exists preferentially as the (1H)-tetrazole iminosaccharin tautomer, where the main stabilizing interaction is the intramolecular H-bond established between the NH group of the saccharyl ring and the tetrazole nitrogen atom in position 4. A detailed conformational analysis of the studied molecule and full assignment of the vibrational spectra for both the matrix-isolated compound and crystalline sample were undertaken.