title: Preparation and guest-uptake protocol for a porous complex useful for 'crystal-free' crystallography.
abstract: We recently reported a new method for single-crystal X-ray diffraction (SCD) analysis that does not require the crystallization of the target compound. In this 'crystal-free' crystallography, a tiny crystal of a porous complex is soaked in the solution of the target guest. The guest molecules are absorbed and oriented in the crystal pores and can be analyzed by X-ray diffraction. We describe here a detailed synthetic protocol for the preparation of uniform single crystals of the porous host complex and for the subsequent guest uptake. The protocol describes our most versatile porous complex, which is prepared from commercially available ZnI2 and 2,4,6-tri(4-pyridyl)-1,3,5-triazine. The host complex has large pores with a cross-section of 8 × 5 Å(2). Single crystals of the complex are grown from layered solutions of the two components. The pores of the as-synthesized complex are filled with nitrobenzene, which is replaced with the inert solvent cyclohexane. This solvent exchange is essential for the rapid and effective inclusion of target compounds. The most crucial and delicate step is the selection of high-quality single crystals from the mixture of crystals of various shapes and sizes. We suggest using the facial indices of the single crystals as a criterion for crystal selection. Single-crystal samples for X-ray analysis can be prepared by immersing the selected crystals in a cyclohexane/dichloromethane solution of target compound. After a very slow evaporation of the solvent, typically over 2 d, the final crystal can be picked and directly subjected to SCD analysis. The protocol can be completed within ∼16 d.
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo, Japan.
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Inokuma
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Yoshioka
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Ariyoshi
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo, Japan.
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Arai
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Fujita
mesh_terms: D053000:Analytic Sample Preparation Methods / Q000379:methods*; D003461:Crystallography / Q000379:methods*; D007454:Iodides / Q000737:chemistry*; D015394:Molecular Structure; D009578:Nitrobenzenes; D016062:Porosity; D014227:Triazines / Q000737:chemistry*; D014961:X-Ray Diffraction; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D007454:Iodides; D009578:Nitrobenzenes; D014227:Triazines; D017967:Zinc Compounds; C029770:zinc iodide; C036077:nitrobenzene; C002849:2,4,6-tripyridyl-s-triazine