title: Understanding the conformational changes and molecular structure of furoyl thioureas upon substitution.
abstract: 1-Acyl thioureas [R1C(O)NHC(S)NR2R3] are shown to display conformational flexibility depending on the degree of substitution at the nitrogen atom. The conformational landscape and structural features for two closely related thioureas having R1=2-furoyl have been studied. The un-substituted 2-furoyl thiourea (I) and its dimethyl analogue, i.e. 1-(2-furoyl)-3,3-dimethyl thiourea (II), have been synthesized and fully characterized by spectroscopic (FT-IR,1H and13C NMR) and elemental analysis. According to single crystal X-ray diffraction analysis, compounds I and II crystallize in the monoclinic space group P21/c. In the compound I, the trans-cis geometry of the almost planar thiourea unit is stabilized by intramolecular NH⋯OC hydrogen bond between the H atom of the cis thioamide and the carbonyl O atom. In compound II, however, the acyl thiourea group is non-planar, in good agreement with the potential energy curve computed at the B3LYP/6-31+G(d,p) level of approximation. Centrosymmetric dimers generated by intermolecular NH⋯SC hydrogen bond forming R22(8) motif are present in the crystals. Intermolecular interactions have been rationalized in terms of topological partitions of the electron distributions and Hirshfeld surface analysis, which showed the occurrence of S⋯H, O⋯H and H⋯H contacts that display an important role to crystal packing stabilization of both thiourea derivatives.
authors.affiliation: Laboratorio de Síntesis Orgánica, Facultad de Química, Universidad de La Habana, La Habana, Cuba.
authors.forename: Raúl Ramos
authors.initials: RR
authors.lastname: Cairo
authors.affiliation: Laboratorio de Síntesis Orgánica, Facultad de Química, Universidad de La Habana, La Habana, Cuba. Electronic address: anap@quimica.uh.cu.
authors.forename: Ana María Plutín
authors.initials: AM
authors.lastname: Stevens
authors.affiliation: Departamento de Química, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
authors.forename: Tamires Donizeth
authors.initials: TD
authors.lastname: de Oliveira
authors.affiliation: Departamento de Química, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
authors.forename: Alzir A
authors.initials: AA
authors.lastname: Batista
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil.
authors.forename: Eduardo E
authors.initials: EE
authors.lastname: Castellano
authors.affiliation: Instituto de Ciencia y Tecnología de Materiales (IMRE), Universidad de La Habana, Havana, Cuba.
authors.forename: Julio
authors.initials: J
authors.lastname: Duque
authors.affiliation: CEQUINOR (UNLP-CONICET, CCT La Plata), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 962 (1900), La Plata, Argentina.
authors.forename: Delia B
authors.initials: DB
authors.lastname: Soria
authors.affiliation: Instituto de Física La Plata, Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 49 y 115, La Plata, Buenos Aires, Argentina.
authors.forename: Adolfo C
authors.initials: AC
authors.lastname: Fantoni
authors.affiliation: Departamento de Química (DeQui), Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto - UFOP, Ouro Preto, Brazil.
authors.forename: Rodrigo S
authors.initials: RS
authors.lastname: Corrêa
authors.affiliation: CEQUINOR (UNLP-CONICET, CCT La Plata), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 962 (1900), La Plata, Argentina. Electronic address: erben@quimica.unlp.edu.ar.
authors.forename: Mauricio F
authors.initials: MF
authors.lastname: Erben
keywords: Hirshfeld surface analysis; Molecular conformation; Single crystal structure determination; Thiourea derivatives; Topological study; Vibrational spectroscopy