title: A commonly used spin label: S-(2,2,5,5-tetramethyl-1-oxyl-delta3-pyrrolin-3-ylmethyl) methanethiosulfonate.
abstract: The title compound, C(10)H(18)NO(3)S(2), which finds application as a spin label, has triclinic (P\overline{1}) symmetry at 100 (2) K with two independent molecules in the asymmetric unit. Both molecules are very similar with respect to bond lengths and angles, but molecule 2 shows disordering of its side chain. The pyrroline rings differ slightly with respect to the position of the NO group, which in both cases are sterically shielded by the surrounding methyl groups. The crystal structure of the title compound represents the first example of a 2,2,5,5-tetramethyl-1-oxyl-Delta(3)-pyrroline derivative with a side chain at the double bond which is linked to it through an sp(3)-hybridized C atom. In the solid state, the side chain adopts a conformation with the methyl group above/below the pyrroline ring and a H atom directed towards a C atom of the double bond. The disordered side chain of molecule 2 represents a second conformation with low potential energy. Both molecules exhibit planar chirality, but in the solid state both pairs of stereoisomers are present. These four stereoisomers are stacked one behind the other in four different columns, denoted A, A', B and B', the angle between the vectors of the N-O bonds in columns A and B being 80.38 (8) degrees .
authors.affiliation: Makromolekülstrukturen, Fachbereich Physik, Universität Osnabrück, Barbarastrasse 7, D-49076 Osnabrück, Germany.
authors.forename: Vitali
authors.initials: V
authors.lastname: Zielke
authors.forename: Henning
authors.initials: H
authors.lastname: Eickmeier
authors.forename: Kalman
authors.initials: K
authors.lastname: Hideg
authors.forename: Hans
authors.initials: H
authors.lastname: Reuter
authors.forename: Heinz Jürgen
authors.initials: HJ
authors.lastname: Steinhoff
mesh_terms: D003460:Crystallization / Q000379:methods; D003461:Crystallography / Q000379:methods; D008698:Mesylates / Q000138:chemical synthesis* / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011758:Pyrroles / Q000138:chemical synthesis / Q000737:chemistry; D013113:Spin Labels / Q000138:chemical synthesis*
chemical_list: D008698:Mesylates; D011758:Pyrroles; D013113:Spin Labels; C013231:pyrroline; C074502:methanethiosulfonate