Modeling the Reaction of Carboxylic Acids and Isonitriles in a Self-Assembled Capsule

Kinetic Resolution of Secondary Alcohols Catalyzed at the Exterior of Chiral Coordinated Capsules

Confined spaces inside molecular hosts can function as reaction vessels. However, this concept significantly limits the scope of reactants. When the exterior of molecular hosts is used instead, we can ease the restriction because reactants are not necessary to be trapped inside molecular hosts, although studies along this line have not been reported. As a proof-of-concept of enantioselective reactions at the exterior of chiral molecular hosts, we utilized host-guest complexes of enantiomerically enriched Cu-coordinated capsules and guests possessing a catalytic center to realize the kinetic resolution of secondary alcohols. Under suitable reaction conditions, a selectivity factor of 2.6 was realized, demonstrating that the reactions occur at the exterior of the capsules. A series of experiments indicated that the substituents on the 2,2'-bipyridyl arms and the alkyl chains on the lower rim contributed to the enantioselectivity of the reactions.

Modeling Amine Methylation in Methyl Ester Cavitand

Methylation of amines inside an introverted resorcinarene-based deep methyl ester cavitand is investigated by means of molecular dynamics simulations and quantum chemical calculations. Experimentally, the cavitand has been shown to bind a number of amines and accelerate the methylation reaction by more than four orders of magnitude for some of them. Eight different amines are considered in the present study, and the geometries and energies of their binding to the cavitand are first characterized and analyzed. Next, the methyl transfer reactions are investigated and the calculated barriers are found to be in generally good agreement with experimental results. In particular, the experimentally-observed rate acceleration in the cavitand as compared to the solution reaction is well reproduced by the calculations. The origins of this rate acceleration are analyzed by computational modifications made to the structure of the cavitand, and the role of the solvent is discussed.

Computational Modeling of Supramolecular Metallo-organic Cages-Challenges and Opportunities

Self-assembled metallo-organic cages have emerged as promising biomimetic platforms that can encapsulate whole substrates akin to an enzyme active site. Extensive experimental work has enabled access to a variety of structures, with a few notable examples showing catalytic behavior. However, computational investigations of metallo-organic cages are scarce, not least due to the challenges associated with their modeling and the lack of accurate and efficient protocols to evaluate these systems. In this review, we discuss key molecular principles governing the design of functional metallo-organic cages, from the assembly of building blocks through binding and catalysis. For each of these processes, computational protocols will be reviewed, considering their inherent strengths and weaknesses. We will demonstrate that while each approach may have its own specific pitfalls, they can be a powerful tool for rationalizing experimental observables and to guide synthetic efforts. To illustrate this point, we present several examples where modeling has helped to elucidate fundamental principles behind molecular recognition and reactivity. We highlight the importance of combining computational and experimental efforts to speed up supramolecular catalyst design while reducing time and resources.