Modifying Enzymatic Substrate Binding within a Metal–Organic Capsule for Supramolecular Catalysis

Abstract

Supramolecular catalysis is established to modify reaction kinetics by substrate encapsulation, but manipulating the thermodynamics of electron-transfer reactions remains unexplored. Herein, we reported a new microenvironment-shielding approach to induce an anodic shift in the redox potentials of hydrazine substrates, reminiscent of the enzymatic activation for N–N bond cleavage within a metal–organic capsule H1. Equipped with the catalytic active cobalt sites and substrate-binding amide groups, H1 encapsulated the hydrazines to form the substrate-involving clathration intermediate, triggering the catalytic reduction N–N bond cleavage when electrons were acquired from the electron donors. Compared with the reduction of free hydrazines, the conceptual molecular confined microenvironment decreases the Gibbs free energy (up to −70 kJ mol–1), which is relevant to the initial electron-transfer reaction. Kinetic experiments demonstrate a Michaelis–Menten mechanism, which involves the formation of the pre-equilibrium of substrate-binding, followed by bond cleavage. Then, the distal N is released as NH3 and the product is squeezed. Integrating fluorescein into H1 enabled the photoreduction of N2H4 with an initial rate of ca. 1530 nmol min–1 into ammonia, comparable to that of natural MoFe proteins; thus, the approach provides an attractive manifold toward mimicking enzymatic activation.

Enzymatic Activation and Continuous Electrochemical Production of Methane from Dilute CO2 Sources with a Self-Healing Capsule

“…While no new peaks were detected when CO 2 was bubbled into the solution, the presence of monoethanolamine 1 aroused a weak proton reduction peak but triggered the emergence of catalytic waves at the more anodic side away from the reduction potential of Fe I /Fe 0 reduction and the CO 2 adduct. Increasing the concentration of 1 -CO 2 resulted in a more positive potential (up to −0.58 V vs NHE) (Figure d). The potential shift exhibited a saturated behavior on the 1 -CO 2 concentration and was controlled by the associated constants for the binding of H1 and its reduced form based on the Nernst equation …”

Host-Guest Complexation-Induced Chirality Switching of Pillararenes by Perylene Diimide-Based Hexagonal Metallacages

“…Metal-coordination-driven self-assembly has proved to be an e cient strategy for the construction of three-dimensional metallacages with con ned nanocavities owing to the good directionality of metalcoordination bonds and their moderate bond strength [34][35][36][37][38][39] . Through ingenious ligand design, metallacages with different shapes, sizes and binding a nities can be e cient prepared in a controllable and predicted manner, making them serve as a type of tunable con ned nanospaces [40][41][42][43][44][45][46][47][48][49][50][51] . In this regard, the charge separation-based multicomponent self-assembly, developed by Stang's and our groups, has made a noteworthy contribution in nely tuning the structures, host-guest chemistry and emission properties of metallacages [52][53] .…”

Supramolecular Handshakes: Characterization of Urea‐Carboxylate Interactions Within Calixarene Frameworks

“…Namely, the role of molecular capsule as a nanoreactor or a drug delivery device implies two basic criteria with respect to the design of a capsular host: a larger cavity and the possibility of reversible opening and closing, followed by the release or capture of a desired cargo. [2][3][4][5][6] A tool that enables these prerequisites is provided by non-covalent synthesis, where self-assembly or hetero-assembly of molecular monomers into a capsule is realized via intermolecular interactions such as metal-ligand coordination bonds, [7][8][9][10][11] hydrogen bonds, [12][13][14] ionic interactions, [15] halogen [16] or chalcogen [17] bonds. The control over the association can be imposed by adjusting the physico-chemical properties of the solution (e. g. pH, [18,19] temperature, ionic strength).…”