The design of artificial catalysts able to compete with the catalytic proficiency of enzymes is an intense subject of research. Non-covalent interactions are thought to be involved in several properties of enzymatic catalysis, notably (i) the confinement of the substrates and the active site within a catalytic pocket, (ii) the creation of a hydrophobic pocket in water, (iii) self-replication properties and (iv) allosteric properties. The origins of the enhanced rates and high catalytic selectivities associated with these properties are still a matter of debate. Stabilisation of the transition state and favourable conformations of the active site and the product(s) are probably part of the answer. We present here artificial catalysts and biomacromolecule hybrid catalysts which constitute good models towards the development of truly competitive artificial enzymes.

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Supramolecular catalysis. Part 2: artificial enzyme mimics

Cooperativity in Noncovalent Interactions.

There is great need for stand-alone luminescence-based chemosensors that exemplify selectivity, sensitivity, and applicability and that overcome the challenges that arise from complex, real-world media. Discussed herein are recent developments toward these goals in the field of supramolecular luminescent chemosensors, including macrocycles, polymers, and nanomaterials. Specific focus is placed on the development of new macrocycle hosts since 2010, coupled with considerations of the underlying principles of supramolecular chemistry as well as analytes of interest and common luminophores. State-of-the-art developments in the fields of polymer and nanomaterial sensors are also examined, and some remaining unsolved challenges in the area of chemosensors are discussed.

/pdf/supramolecular-luminescent-sensors-1rs45r4um4.pdf

Supramolecular Luminescent Sensors

The study of the noncovalent force between π-acidic aromatic systems and anions, referred to as the anion−π interaction, has recently emerged as a new branch of supramolecular chemistry. The anion−π contact is complementary to the cation−π interaction, a prominent noncovalent force involved in protein structure and enzyme function. Until recently, the scientific community had overlooked the anion−π interaction due to its ostensibly counterintuitive nature. Pioneering theoretical studies in 2002, however, established that anion−π interactions are energetically favorable (∼20–70 kJ/mol) and prompted a flurry of reports in support of their existence. The interest in anion−π contacts was further fueled by the importance of anions in key chemical and biological processes and the involvement of π-rings in anion recognition and transport. Anion−π interactions hold great promise for the design of selective anion receptors, hosts or scaffolds, colorimetric sensors, and catalysts and may also affect biological func...

Anion-π interactions in supramolecular architectures.

A fluorescent organic cage for picric acid detection

Brothers and enemies: Anion-π and cation-π interactions act in a synergistic way when gathered in the molecular cavity of a hemicryptophane host, affording an efficient contribution (-170 kJ mol(-1)) in zwitterion recognition. NMR titration experiments and calculations reveal the positioning of the guest in the cavity of the heteroditopic receptor. This study emphasizes the importance of anion-π bonds in host-guest chemistry.

Combined cation-π and anion-π interactions for zwitterion recognition.

Oxidation of cycloalkanes by H2O2 using a copper–hemicryptophane complex as a catalyst

The heteroditopic hemicryptophane 1, which bears a tripodal anion binding site and a cation recognition site in the molecular cavity, proved to be an efficient ion-pair receptor. The hemicryptophane host binds anions selectively depending on shape and hydrogen-bond-accepting ability. It forms an inclusion complex with the Me(4)N(+) ion, which can simultaneously bind anionic species to provide anion@[1⋅Me(4)N(+)] complexes. The increased affinity of [1⋅Me(4)N(+)] for anionic species is attributed to a strong cooperative effect that arises from the properly positioned binding sites in the hemicryptophane cavity, thus allowing the formation of the contact ion pair. Density functional theory calculations were performed to analyze the Coulomb interactions of the ion pairs, which compete with the ion-dipole ones, that originate in the ion-hemicryptophane contacts.

Olivier Perraud

Papers

Combined cation-π and anion-π interactions for zwitterion recognition.

Oxidation of cycloalkanes by H2O2 using a copper–hemicryptophane complex as a catalyst

The cooperative effect in ion-pair recognition by a ditopic hemicryptophane host.

Exclusive enantioselective recognition of glucopyranosides by inherently chiral hemicryptophanes.

Shorter and modular synthesis of hemicryptophane-tren derivatives.