title: Synthesis and Structural Characterization of 1-Arylimidazole-2-thiones andN,N'-Aryldiethoxyethylthioureas with Electronically Diverse Substituents: A Manifold of Hydrogen Bonding Networks.
abstract: The 1-arylimidazole-2-thiones, (HmimAr) [Ar = 3,4,5-C6H2(OMe)3, 2,4-C6H3(NO2)(OMe), 2,4,6-C6H2Cl3and 3,5-C6H3(CF3)2], which feature electronically diverse substituents, may be obtainedviaacid-catalyzed ring closure of the correspondingN,N'-aryldiethoxyethylthiourea derivatives, ArN(H)C(S)N(H)CH2CH(OEt)2, (H2detuAr), which in turn are obtainedviatreatment of aminoacetaldehyde diethyl acetal, H2NCH2CH(OEt)2, with the respective arylisothiocyanates (ArNCS). The molecular structures of all of the aboveN,N'-aryldiethoxyethylthioureas and 1-arylimidazole-2-thiones have been determined by X-ray diffraction, thereby demonstrating that the substituents have a profound effect on the crystal structures. For example, each of theN,N'-aryldiethoxyethylthiourea derivatives adopts a different hydrogen bonding pattern. Specifically, the hydrogen-bonding network in(i)H2detuArCl3consists of chains of 9-membered rings, with an [ [Formula: see text](9)] motif, that feature one N-H ⋯ O and one N-H ⋯ S interaction,(ii)H2detuArOMe,NO2consists of chains of 6-membered rings, with an [ [Formula: see text](6)] motif, that feature two head-to-tail N-H ⋯ S interactions,(iii)H2detuAr(CF3)2consists of a dimer that features two pairs of N-H ⋯ O interactions, of which each pair is a component of an 8-membered ring with an [ [Formula: see text](8)] motif, and(iv)H2detuAr(OMe)3consists of a chain of head-to-head dimeric rings with a basic [ [Formula: see text](16)] motif, a notable feature of which is that sulfur does not play a role as a hydrogen bond acceptor. Each of the 1-arylimidazole-2-thiones exists as a "head-to-head" hydrogen-bonded dimer in the solid state, with an [ [Formula: see text](8)] motif. However, while the hydrogen-bonded motifs for HmimArCl3and HmimAr(OMe)3are planar, those for HmimAr(CF3)2and HmimArOMe,NO2are extremely puckered, with fold angles of 24.2° (mean value) and 45.7°, respectively.
authors.affiliation: Department of Chemistry, Columbia University, New York, New York 10027, USA.
authors.forename: Joshua H
authors.initials: JH
authors.lastname: Palmer
authors.affiliation: Department of Chemistry, Columbia University, New York, New York 10027, USA.
authors.forename: Gerard
authors.initials: G
authors.lastname: Parkin