title: Structural aspects of two α-dihydrazones displaying a complete survey of intermolecular interactions.
abstract: The compounds (2'E,2'E)-2,2'-(propane-1,2-diylidene)bis[1-(2-nitrophenyl)hydrazine], C15H14N6O4, (I), and (2Z,3Z)-ethyl 3-[2-(2-nitrophenyl)hydrazinylidene]-2-[2-(4-nitrophenyl)hydrazinylidene]butanoate tetrahydrofuran hemisolvate, C18H18N6O6·0.5C4H8O, (II), are puzzling outliers deviating from a general synthetic route aimed at the preparation of substituted pyrazoles. Possible reasons for this outcome, which is exceptional in an otherwise firmly established synthetic procedure, are analyzed. Compound (I) is unsolvated, while compound (II) crystallizes with a tetrahydrofuran solvent molecule lying on an inversion centre. The ethoxycarbonyl chain of (II), in turn, appears disordered into two equally populated (50%) moieties. In both structures, a plethora of different commonly occurring weak intermolecular interactions [viz. π(phenyl)...π(phenyl), π(C=N)...π(C=N), π(phenyl)...π(C=N), N-H...O and C-H...O] appear responsible for the crystal stability. Much less common are the short O(nitro)...O(nitro) contacts which are observed in the structure of (I), an example of unusual `electron donor-acceptor' (EDA) interactions.
authors.affiliation: Instituto de Química, Universidad Austral de Chile, Las Encinas 220, Casilla 567, Valdivia, Chile.
authors.forename: Carlos
authors.initials: C
authors.lastname: Bustos
authors.affiliation: Departamento de Ciencias Físicas, Universidad Andrés Bello, República 220, Santiago de Chile, Chile.
authors.forename: Luis
authors.initials: L
authors.lastname: Alvarez-Thon
authors.affiliation: Gerencia de Investigación y Aplicaciones, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Buenos Aires, Argentina.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Baggio
keywords: crystal structure; electron donor–acceptor (EDA) interactions; ester; hydrazines; short O...O contacts; substituted pyrazoles; α-dihydrazones