Crystal structure of 1-iodo-3-{[4-(tert-butylsulfanyl)phenyl]ethynyl}azulene

The title compound, C20H19IS, features a 1,3-disubstituted azulene involving an ethynylene elongated 4-(tert-butylsulfanyl)phenyl sidearm and an iodine atom as the substituents. The azulene ring system is almost planar (r.m.s. deviation = 0.012 Å) and subtends a dihedral angle of 35.7 (1)° with the benzene ring. As a result of the inherent dipole character of the azulene core, a supramolecular π–π dimer [separation between the centroids of the five- and seven-membered rings = 3.7632 (10) Å] with antiparallel orientated molecules can be observed in the crystal. The packing is consolidated by an unusual I...π(acetylene) contact [I...Cg = 3.34 Å, C—I...Cg = 173.3°], and a very weak C—H...π interaction is also found in the structure, with the azulene five-membered ring as the acceptor.