4,6-Bis[4-(benzylsulfanyl)styryl]-2-(methylsulfanyl)pyrimidine

The title compound, C35H30N2S3, has been synthesized by a solvent-free reaction. The molecule exhibits an E,E configuration, the benzene rings and pyrimidine rings being located on the opposite sides of the C=C bonds. The centroid–centroid separation of 3.5808 (17) Å indicates the existence of π–π stacking between nearly parallel pyrimidine and benzene rings of adjacent molecules.

The title compound, C 35 H 30 N 2 S 3 , has been synthesized by a solvent-free reaction. The molecule exhibits an E,E configuration, the benzene rings and pyrimidine rings being located on the opposite sides of the C C bonds. The centroidcentroid separation of 3.5808 (17) Å indicates the existence of stacking between nearly parallel pyrimidine and benzene rings of adjacent molecules.

S1. Comment
Two-photon absorption (TPA) processes in conjugated organic molecules have aroused considerable attention due to their potential applications in optical data storage, three-dimension fluorescence imaging, photodynamic therapy, two-photon upconversion lasing and three-dimension lithographic microfabrication (Frederiksen et al., 2001;Zhao et al., 1995). A sustained level of fundamental research over the past ten years has left organic nonlinear optical (NLO) well positioned to make a technological impact in a variety of disciplines. Some studies showed that the heterocycle-based two-photon absorbing chromophores exhibit large TPA cross-sections (Huang et al., 2003). As part of our ongoing investigtion on heterocycle-based two-photon absorbing chromophores, the title compound has been prepared and its crystal structure is presented here.

S2. Experimental
At room temperature, t-BuOK (5.6 g, 50 mmol) was placed into a dry mortar and milled to very small, then 2-thiomethyl-4,6-dimethylpyrimidine (1.54 g, 10 mmol) and 4-benzylthiobenzalaldehyde (4.56 g, 20 mmol) were added and mixed. The mixture was milled vigorously for about 20 min. The mixture became sticky and then continuously milled for 10 min. After completion of the reaction (monitored by TLC), the mixture was dispersed in 100 ml me thanol. The residual solid was filtered and recrystallized from anhydrous dichloromethane/methanol solution, to give microcrystals (2.87 g, yield 50%). Single crystals suitable for X-ray analysis were obtained by slow evaporation from a dichloromethane/2-propanol (3:1) solution.

S3. Refinement
The H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93 or 0.96 Å and U iso (H) = 1.2 or 1.5U eq (C).  The molecular structure of the title compound with 30% probability displacement ellipsoids for non-H atoms.

Data collection
Bruker SMART CCD area detector diffractometer Radiation source: fine-focus sealed tube Graphite monochromator φ and ω scans Absorption correction: multi-scan (SADABS; Sheldrick, 1996) T min = 0.875, T max = 0.920 7820 measured reflections 5185 independent reflections 3229 reflections with I > 2σ(I) 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.