2,3-Bis(3-fluorophenyl)tetrazolium-5-thiolate

The zwitterionic title compound, C13H8F2N4S, is situated on a twofold rotation axis running along the C—S [1.691 (2) Å] single bond. The phenylene ring is twisted out of the tetrazolium plane by 42.18 (7)°. Relatively short distances [3.7572 (9) and 4.0625 (6) Å] between the centroids of the phenylene and tetrazolium rings of neighbouring molecules suggest π–π interactions. The crystal under investigation was a non-merohedral twin, with a 33% twin component.

The zwitterionic title compound, C 13 H 8 F 2 N 4 S, is situated on a twofold rotation axis running along the C-S [1.691 (2) Å ] single bond. The phenylene ring is twisted out of the tetrazolium plane by 42.18 (7) . Relatively short distances [3.7572 (9) and 4.0625 (6) Å ] between the centroids of the phenylene and tetrazolium rings of neighbouring molecules suggestinteractions. The crystal under investigation was a non-merohedral twin, with a 33% twin component.

Comment
During the process of synthesizing a series of electronically altered dithizones for the purpose of investigating its effect on the photochromic isomerization reaction of metal dithizonates, several phenyl substituted species were fully oxidized to its dehydrodithizone derivatives. Dehydrodithizones, most probably due to their zwitter-ionic nature, crystallizes much more readily than the parent compound. The yellow meta-fluoro dehydrodithizone crystals, suitable for X-ray crystallography, were isolated from a mixture of polar solvents, i.e. acetone and water.
The title compound crystallizes in the monoclininc space group C2/c (Z = 4) resulting in molecules lying on special positions in the crystal lattice. All bond lengths and angles (see Table 1, Fig. 1) are within range of their expected values (Allen et al., 1987). The phenyl rings adopt a non-parallel arrangement with the dehydrodithizone backbone with dihedral angles of 42.18 (7)° for ring C2-C7, mainly due to their close proximities on the tetrazole moiety. The preferred orientation is supported by the π-π stacking of the phenyl rings of neighbouring molecules (distance between planes = 3.4069 Å, centroid to centroid distance = 3.7572 (9) Å). Similar π-π stacking is also observed between neighbouring tetrazole moieties in a head-to-head fashion (distance between planes = 3.4235 Å, centroid to centroid distance = 4.0625 (6) Å) Additionally, several other close contacts/interactions are noted, among these a rather close contact for C6-H6···S between neighbouring dithizone molecules.

Refinement
The aromatic H atoms were placed in geometrically idealized positions (C-H = 0.95 Å) and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C). Initial CheckCIF evaluation indicated possible non-merohedral twinning, and the data was subsequantly treated using CELL_NOW to obtain orientation matrix of the two components. The raw data was supplementary materials sup-2 then integrated as two components resulting in a HKLF5 format file, which greatly improved refinement parameters and yielded the refined composition of the twinned domains in a 33.1:66.9 ratio. Fig. 1. View of (I) (30% probability displacement ellipsoids). Accented lettering indicate atoms generated by symmetry (-x, y, 1/2 -z).

Special details
Experimental. The intensity data was collected on a Bruker X8 Apex II 4 K Kappa CCD diffractometer using an exposure time of 180 s/frame. A total of 791 frames were collected with a frame width of 0.5° covering up to θ = 28.36° with 98.9% completeness accomplished.
Geometry. All e.s. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S 0 0.63767 (5)