Content area
Full text
Editorial
Nature continuously inspires scientists to design novel prototypes of artificial systems with more and more advanced functions and properties [1.2]. In this regard, one of the greatest innovations was the discovery that small molecules can catalyze/mediate chemical reactions by a biomimetic approach [3.4]. Very recently, many efforts have been devoted to study supramolecular catalysis processes [5-14] in which macrocyclic hosts, self-assembled capsules and metallo-cages were employed as catalysts or nanocontainers.
The primary characteristic of supramolecular catalysis is that the general modes of activation based on intermolecular interactions can operate on substrates in a selective way. and in confined environment, like the active site of natural enzymes [5-14]. As a result, molecular recognition of the substrate(s ) and potentially the transition state is essential in supramolecular catalysis.
Supramolecular catalysis finds inspiration in natural enzymes, which show catalytic features such as substrates and products selectivity, efficiency, geometric control, and acceleration of chemical reactivity [1]. If reactants are confined in the restricted space provided by an enzyme binding pocket, the increase in local concentration, due to the proximity effect, the stabilization of intermediates and transition states cause the acceleration of the reaction. Thus, learning from natural enzymes, novel supramolecular catalysts were designed that showed substrate selectivity, turnover, regioselectivity, and stereoselectivity [5-14],
Supramolecular architectures with an internal cavity are potential candidates to work as supramolecular catalysts [5-14]. The first supramolecular catalysts were based on covalent hosts, typically cyclodextrin macrocycles [1], which had an interior hydrophobic cavity decorated with catalytically useful functional groups. Recently, increased emphasis has been placed on catalysis that takes use of noncovalent hosts, including selfassembled capsules [5.6.8.9]. The capsules feature sizeable internal hydrophobic cavities that can accommodate large substrates and even allow bimolecular reactions to take place. In addition, they may ensure catalytic turnover. Transition states and reaction intermediates may also be stabilized in the cavities of the capsules by means of intermolecular interactions. The most intriguing aspect of catalysis in confined spaces [5-14] is that the reactions can take place through unusual mechanisms. This is mainly due to the conformational control of the substrates, steric constrictions, stabilization of species, and solvent exclusion phenomena occurring in the molecular containers isolated spaces [6]. Consequently, the classical rules of organic reactivity are often violated [6,11].
Taking...