6a,6b,12a,12b-Tetrahydrocycloocta[3,4]cyclobuta[1,2][8]annulene

The cis,syn,cis-tricyclic [2+2]-dimer of cyclooctatetraene, C(16)H(16), crystallizes in space group Pca2(1) with two molecules in the asymmetric unit. An extensive network of weak C-H...pi(C[double bond]C) interactions between the two independent molecules, A and B, as well as A...A and B...B interactions, are observed in the supramolecular assembly. The C-H groups point more towards one C atom than to the centre of the C[double bond]C bond. Notable among the interactions are bifurcated (cyclobutane)C-H...C[double bond]C contacts that span transannularly the eight-membered ring.