Face-selective adsorption of a prochiral compound on the chiral pore-surface of a metal-macrocycle framework (MMF) directed towards stereoselective reactions.

Molecular adsorption on a surface is a unique way to break the mirror-symmetry of prochiral molecules, and therefore the use of chiral surfaces is an effective strategy for achieving highly selective chiral separation and asymmetric catalytic reactions based on molecular adsorption with high diastereoselectivity. We have previously reported a porous metal-macrocycle framework (MMF) with an enantiomeric pair of chiral pore-surfaces derived from Pd-helical macrocycles as the ingredients of the framework. Aiming at applying the chiral pore-surface of the MMF to asymmetric reactions and chiral separation, herein we propose a strategy to utilize one of the enantiomerically paired pore-surfaces as a homochiral pore-surface with the aid of chiral auxiliaries that can block only one side of the enantiomeric pore-surfaces in a site-selective manner. Single-crystal X-ray diffraction analysis revealed that a chiral auxiliary, (1R)- or (1S)-1-(3-chlorophenyl)ethanol, and a prochiral guest molecule, 2'-hydroxyacetophenone, were cooperatively arranged in each pore unit so that the prochiral guest molecule can face-selectively bind to the homochiral pore-surface.

Rational synthesis of benzimidazole[3]arenes by CuII-catalyzed post-macrocyclization transformation.

A new series of calix[n]arene analogues, benzimidazole[3]arenes, was rationally synthesized by CuII-catalyzed post-macrocyclization transformation of a tris(o-phenylenediamine) macrocycle, and fully characterized by NMR, MS, and single-crystal X-ray diffraction (XRD) analyses. The resulting syn- and anti-benzimidazole[3]arenes have a bowl-shaped and a warped structure, respectively, in their crystalline states, and both display a dynamic inversion behavior in solution. This modification resulted in strong fluorescence due to the generated benzimidazole moieties. The mechanistic study of the post-macrocyclization transformation demonstrated that the formation of both benzimidazole[3]arenes was catalyzed, via triimine intermediates, by CuII ions in air through oxidation and cyclization of the tris(o-phenylenediamine) macrocycle.

Non-covalent immobilisation of p-toluenesulfonic acid in a porous molecular crystal for size-specific acid-catalysed reactions.

Non-covalent immobilisation of catalysts in nanoporous materials is a promising way to apply homogeneous catalysts to heterogeneous catalytic reactions. Herein we report a size-specific catalytic reaction with an acid catalyst, p-toluenesulfonic acid, immobilised in a porous molecular crystal, metal-macrocycle framework (MMF), composed of metallo-macrocycles. A tritylated substrate which is smaller than the pore dimension of MMF was deprotected by the heterogeneous catalyst, whereas the reaction with a larger substrate was completely suppressed due to the steric restriction.

Simultaneous arrangement of up to three different molecules on the pore surface of a metal-macrocycle framework: cooperation and competition.

Porous crystals are excellent materials with potential spatial functions through molecular encapsulation within the pores. Co-encapsulation of multiple different molecules further expands their usability and designability. Herein we report the simultaneous arrangement of up to three different guest molecules, TTF (tetrathiafulvalene), ferrocene, and fluorene, on the pore surfaces of a porous crystalline metal-macrocycle framework (MMF). The position and orientation of adsorbed molecules arranged in the pore were determined by single-crystal X-ray diffraction analysis. The anchoring effect of hydrogen bonds between the hydroxy groups of the guest molecules and inter-guest cooperation and competition are significant factors in the adsorption behaviors of the guest molecules. This finding would serve as a design basis of multicomponent functionalized nanospaces for elaborate reactions that are realized in enzymes.