title: Two tautomers in the same crystal: 3-(4-fluoro-phen-yl)-1H-pyrazole and 5-(4-fluoro-phen-yl)-1H-pyrazole.
abstract: The title co-crystal, 3-(4-fluoro-phen-yl)-1H-pyrazole-5-(4-fluoro-phen-yl)-1H-pyrazole (1/1), C9H7FN2, crystallizes with four independent mol-ecules (A, B, C and D) in the asymmetric unit exhibiting two tautomeric forms (A and D; B and C) due to N-H proton exchange between the two N atoms of the pyrazole ring. The dihedral angles between the mean planes of the pyrazole and benzene rings are 15.6 (1), 19.8 (9), 14.0 (1) and 10.7 (7)° in mol-ecules A, B, C and D, respectively. In the crystal, N-H⋯N hydrogen bonds link the four mol-ecules in the asymmetric unit into a ring with an R 4 (4)(12) motif. Furthermore, weak C-H⋯F inter-actions link the mol-ecules into a three-dimensional network.
authors.affiliation: Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, India.
authors.forename: Thammarse S
authors.initials: TS
authors.lastname: Yamuna
authors.affiliation: Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, India.
authors.forename: Manpreet
authors.initials: M
authors.lastname: Kaur
authors.affiliation: Department of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA.
authors.forename: Jerry P
authors.initials: JP
authors.lastname: Jasinski
authors.affiliation: Department of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Anderson
authors.affiliation: Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, India.
authors.forename: H S
authors.initials: HS
authors.lastname: Yathirajan
keywords: crystal structure; hydrogen bonds; pyrazole derivative; tautomeric forms