title: Isomorphism and solid solution as shown by an accurate high-resolution diffraction experiment.
abstract: High-resolution crystal structure determination and spherical and multipolar refinement enabled an organic solid solution of 1-(4'-chlorophenyl)-2-methyl-4-nitro-1H-imidazole-5-carbonitrile and 5-bromo-1-(4'-chlorophenyl)-2-methyl-4-nitro-1H-imidazole to be found, which would not normally be revealed using only standard resolution data (ca 0.8 Å), as the disordered part is only visible at high resolution. Therefore, this new structure would have been reported as just another polymorphic form, even more reasonably as isostructural with other derivatives. To the best of our knowledge this is the first example of organic solid solution modelled via charge density Hansen-Coppens formalism and analysed by means of quantum theory of atoms in molecules (QTAIM) theory.
authors.affiliation: Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Poulain
authors.affiliation: Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Kubicki
authors.affiliation: Cristallographie, Résonance Magnétique et Modelisations, CRM2, UMRCNRS-UL 7036, Institut Jean Barriol, Université de Lorraine, BP 70239, 54506 Vandoeuvre-les-Nancy, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Lecomte
keywords: anharmonicity; crystal engineering; experimental charge density; isomorphism; multipolar parameters; multipole Hansen–Coppens model; organic solid solution; polymorphism; transferability