Unexpected formation of a co-crystal containing the chalcone (E)-1-(5-chloro-thio-phen-2-yl)-3-(3-methyl-thio-phen-2-yl)prop-2-en-1-one and the keto-enol tautomer (Z)-1-(5-chloro-thio-phen-2-yl)-3-(3-methyl-thio-phen-2-yl)prop-1-en-1-ol.

The title crystal structure is assembled from the superposition of two mol-ecular structures, (E)-1-(5-chloro-thio-phen-2-yl)-3-(3-methyl-thio-phen-2-yl)prop-2-en-1-one, C(12)H(9)ClOS(2) (93%), and (Z)-1-(5-chloro-thio-phen-2-yl)-3-(3-methyl-thio-phen-2-yl)prop-1-en-1-ol, C(12)H(11)ClOS(2) (7%), 0.93C(12)H(9)ClOS(2)·0.07C(12)H(11)ClOS(2). Both were obtained from the reaction of 3-methyl-thio-phene-2-carbaldehyde and 1-(5-chloro-thio-phen-2-yl)ethanone. In the extended structure of the major chalcone component, mol-ecules are linked by a combination of C-H⋯O/S, Cl⋯Cl, Cl⋯π and π-π inter-actions, leading to a compact three-dimensional supra-molecular assembly.