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-butyl-sulfanyl)-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 supra-molecular π-π dimer [separation between the centroids of the five- and seven-membered rings = 3.7632 (10) Å] with anti-parallel orientated mol-ecules can be observed in the crystal. The packing is consolidated by an unusual I⋯π(acetyl-ene) contact [I⋯Cg = 3.34 Å, C-I⋯Cg = 173.3°], and a very weak C-H⋯π inter-action is also found in the structure, with the azulene five-membered ring as the acceptor.