title: Crystal structure of minoxidil at low temperature and polymorph prediction.
abstract: An experimental and theoretical investigation on crystal forms of the popular and ubiquitous pharmaceutical Minoxidil is presented here. A new crystallization method is presented for Minoxidil (6-(1-piperidinyl)-2,4-pyrimidinediamide 3-oxide) in ethanol-poly(ethylene glycol), yielding crystals with good quality. The crystal structure is determined at low temperature, with a final R value of 0.035, corresponding to space group P2(1) (monoclinic) with cell dimensions a = 9.357(1) A, b = 8.231(1) A, c = 12.931(2) A, and beta = 90.353(4) degrees . Theoretical calculations of the molecular structure of Minoxidil are set forward using empirical force fields and quantum-mechanical methods. A theoretical prediction for Minoxidil crystal structure shows many possible polymorphs. The predicted crystal structures are compared with X-ray experimental data obtained in our laboratory, and the experimental crystal form is found to be one of the lowest energy polymorphs.
authors.affiliation: Laboratorio de Estudios Cristalográficos, Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. Fuentenueva s/n, 18002-Granada, Spain.
authors.forename: Africa P
authors.initials: AP
authors.lastname: Martín-Islán
authors.forename: Daniel
authors.initials: D
authors.lastname: Martín-Ramos
authors.forename: C Ignacio
authors.initials: CI
authors.lastname: Sainz-Díaz
mesh_terms: D003460:Crystallization; D006860:Hydrogen Bonding; D008914:Minoxidil / Q000737:chemistry*; D008958:Models, Molecular; D013696:Temperature; D013816:Thermodynamics
chemical_list: D008914:Minoxidil