2-(2,4-Dichlorophenoxymethyl)-5-(4-methylphenyl)imidazo[2,1-b][1,3,4]thiadiazole1

In the title compound, C18H13Cl2N3OS, the eight atoms comprising the central imidazo/thiadiazolethiadiazole residue are coplanar (r.m.s. deviation = 0.009 Å). The dihedral angle of 8.72 (13)° between the dichlorobenzene and tolyl rings reflects a twist about the O—C(benzene) bond; the Cm—O—Cb—Cb torsion angle = −168.5 (2)° (m = methylene C and b is benzene C). Supramolecular tapes along the b axis are found in the crystal structure which are mediated by π–π interactions occurring between centrosymmetrically related thiadiazole rings [inter-ring centroid distance = 3.6907 (16) Å] and between the benzene and tolyl rings [inter-ring centroid distance = 3.7597 (16) Å].

In the title compound, C 18 H 13 Cl 2 N 3 OS, the eight atoms comprising the central imidazo/thiadiazolethiadiazole residue are coplanar (r.m.s. deviation = 0.009 Å ). The dihedral angle of 8.72 (13) between the dichlorobenzene and tolyl rings reflects a twist about the O-C(benzene) bond; the C m -O-C b -C b torsion angle = À168.5 (2) (m = methylene C and b is benzene C). Supramolecular tapes along the b axis are found in the crystal structure which are mediated byinteractions occurring between centrosymmetrically related thiadiazole rings [inter-ring centroid distance = 3.6907 (16) Å ] and between the benzene and tolyl rings [inter-ring centroid distance = 3.7597 (16) Å ].   In the crystal packing, molecules aggregate into tapes along the b axis via π-π interactions occurring between centrosymmetrically related thiadiazole rings [inter-ring centroid distance = 3.6907 (16) Å for symmetry operation: 2 -x, -y, 1 -z] and between the benzene and tolyl rings [inter-ring centroid distance = 3.7597 (16) Å for symmetry operation: 2 Fig. 2. Columns stack with no specific interactions between them, Fig. 3.

Experimental
The title compound was prepared according to the reported method (Abdel-Wahab et al., 2011). Colourless crystals were obtained from DMF solution by slow evaporation at room temperature.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.93 to 0.97 Å) and were included in the refinement in the riding model approximation, with U iso (H) = 1.2U equiv (C) or 1.5U equiv (C).  The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level.

Figure 2
A view of the supramolecular tape along the b axis in (I) mediated by π-π interactions shown as purple dashed lines.  A view of the crystal packing in projection down the b axis. The π-π interactions are shown as purple dashed lines. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.27 e Å −3 Δρ min = −0.24 e Å −3

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 R-factors(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.