Crystal engineering through non-bonded contacts to sulphur : structure and solid state photoreactivity of 4-(4'-chloro)-phenyl-Δ-4-thiazolene-2-thione

Abstract

Weak but directionally specific interstack S....S and S....Cl contacts may be used to engineer the 4 Å -short axis β -structure for a planar sulphur heterocycle. A representative compound is the title thione 2. Crystals of 2 are monoclinic, P2¹/n, Z=8, a=17.327(4), b=3.950(2), c=27.877(6) Å, B=93.88(2)° ; R=0.050, R_w=0.044 on 783 non-zero reflections. Molecules related by translation along [010] are within photoreactive distance and the β -structure leads to the rapid formation on UV irradiation of a fused tricyclic mirror symmetry cyclobutane 3. This dimer is very unstable and collapses thermally to the novel ten-membered diolefin 4. The β -packing mode is adopted by several other related sulphur heterocycles.