title: Structure and photochemistry of a saccharyl thiotetrazole.
abstract: The molecular structure and photochemistry of 5-thiosaccharyl-1-methyltetrazole (TSMT) were studied by means of matrix-isolation FTIR spectroscopy, X-ray crystallography, and theoretical calculations. The calculations predicted two conformers of TSMT that differ in energy by more than 15 kJ mol(-1). The infrared spectrum of TSMT isolated in solid argon was fully assigned on the basis of the spectrum calculated (O3LYP/6-311++G(3df,3pd)) for the most stable conformer. In the crystal, TSMT molecules were found to assume the same conformation as for the isolated molecule, with each molecule forming four hydrogen bonds with three neighboring molecules, leading to a network of TSMT oligomers. Upon UV (λ = 265 nm) irradiation of the matrix-isolated TSMT, two photodegradation pathways were observed, both arising from cleavage of the tetrazolyl ring. Pathway a involves cleavage of the N1-N2 and N3-N4 bonds with extrusion of N2, leading to photostable diazirine and thiocarbodiimide derivatives. The photostability of the photoproduced diazirine under the conditions used precluded its rearrangement to the nitrile imine, as reported for 5-phenyltetrazole by Bégué et al. ( J. Am. Chem. Soc. 2012 , 134 , 5339 ). Pathway b involves cleavage of the C5-N1 and N4-N3 bonds, leading to a thiocyanate and methyl azide, the latter undergoing subsequent fragmentation to give CNH.
authors.affiliation: †CCMAR and Department of Chemistry and Pharmacy, F.C.T., University of Algarve, P-8005-039 Faro, Portugal.|‡Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Ismael
authors.affiliation: ‡Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Borba
authors.affiliation: §CEMDRX, Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal.
authors.forename: M S C
authors.initials: MS
authors.lastname: Henriques
authors.affiliation: §CEMDRX, Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal.
authors.forename: J A
authors.initials: JA
authors.lastname: Paixão
authors.affiliation: ‡Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal.
authors.forename: R
authors.initials: R
authors.lastname: Fausto
authors.affiliation: †CCMAR and Department of Chemistry and Pharmacy, F.C.T., University of Algarve, P-8005-039 Faro, Portugal.
authors.forename: M L S
authors.initials: ML
authors.lastname: Cristiano