Dynamic negative allosteric effect: regulation of catalysis via multicomponent rotor speed.

Nanorotor R1 (420 kHz) was assembled from five components utilizing three orthogonal interactions. Post-modification at the distal position generated the advanced six component rotor R2 (45 kHz). The decrease in R2 speed leads to the inhibition of a three-component reaction by reducing catalyst release.

Dissipative sequential catalysis via six-component machinery.

Triphenyl phosphane (TPP) and an epoxide as a fuel system transiently transformed a non-catalytic six-component turnstile into a four-component catalytic rotor releasing N-methyl pyrrolidine and a copper(I) complex. The two latter compounds acted synergistically as catalysts to perform first a Michael addition and then a 5-exo-dig cyclization, giving rise to dissipative sequential catalysis.

Mechanistic insights into on-surface reactions from isothermal temperature-programmed X-ray photoelectron spectroscopy.

On-surface synthesis often proceeds under kinetic control due to the irreversibility of key reaction steps, rendering kinetic studies pivotal. The accurate quantification of reaction rates also bears potential for unveiling reaction mechanisms. Temperature-Programmed X-ray Photoelectron Spectroscopy (TP-XPS) has emerged as an analytical tool for kinetic studies with splendid chemical and sufficient temporal resolution. Here, we demonstrate that the common linear temperature ramps lead to fitting ambiguities. Moreover, pinpointing the reaction order remains intricate, although this key parameter entails information on atomistic mechanisms. Yet, TP-XPS experiments with a stepped temperature profile comprised of isothermal segments facilitate the direct quantification of rate constants from fitting time courses. Thereby, rate constants are obtained for a series of temperatures, which allows independent extraction of both activation energies and pre-exponentials from Arrhenius plots. By using two analogous doubly versus triply brominated aromatic model compounds, we found that their debromination on Ag(111) is best modeled by second-order kinetics and thus proceeds via the involvement of a second, non-obvious reactant. Accordingly, we propose that debromination is activated by surface supplied Ag adatoms. This hypothesis is supported by Density Functional Theory (DFT) calculations. We foresee auspicious prospects for this TP-XPS variant for further exploring the kinetics and mechanisms of on-surface reactions.

Stepwise Dissipative Control of Multimodal Motion in a Silver(I) Catenate.

Stepwise dissipative control of two distinct motions, i.e., shuttling and sliding, is demonstrated in a single multicomponent device. When [2]rotaxane 1, which acts as a biped, and deck 2 were treated with AgBF4/PhCH2Br+NEt3 as chemical fuel, the transient catenate [Ag(1)]+ ⋅ [Ag3(2)]3+ was instantly generated showing multimodal motion and autonomous return to 1 and 2. In the dissipative process, catenate [Ag(1)]+ ⋅ [Ag3(2)]3+ cleanly transformed into the follow-up transient device (1) ⋅ [Ag3(2)]3+ exhibiting only sliding motion. Two interference-free dissipative cycles proved the resilience and robustness of the process.

Interconversion between multicomponent slider-on-deck and palladium capsule: regulation of catalysis and encapsulation.

When the slider-on-deck [Cu3(1)(2)]3+ and guest G were treated with palladium(II) ions, the biped 2 was released from [Cu3(1)(2)]3+ generating the nanocage [Pd2(2)4(G)]4+ with guest G being encapsulated (NetState-II). This transformation that was reversed by the addition of DMAP enabled modulation of both the overall fluorescence and the activity of copper(I) catalyzing an aza Hopf cyclization.

Chemically Fueled Logic AND Gate with Double Encoding in the Time Domain.

To increase information density and security in communication, Nature at times encodes signals in the time domain, for instance, Ca2+ ion signals. Double encoding in the time domain operates beyond this level of security because the data are encoded in two time-dependent output signals showing distinct periods, frequencies, and full duration half-maxima. To illustrate such a protocol, a three-component ensemble consisting of a double ion-selective luminophore with two distinct receptor sites, hexacyclen, and diaza-18-crown-6 ether is demonstrated to act as a logic AND gate with Ag+ and Ca2+ ions as inputs. The gate shows an unprecedented 2-fold time-encoded fluorescence output at 590 and 488 nm based on metal ion pulses with distinct periods when trichloroacetic acid is applied as chemical fuel.

Orthogonal Initiation of Molecular Motion Devices by Two Chemical Fuels.

Herein, we demonstrate the selective dissipative and orthogonal actuation of two distinct molecular devices controlled by alternate fuel use. When the multicomponent ensemble of [2]rotaxane 1 and turnstile [Cu(2)(3)]+ was charged with AgBF4 as chemical fuel (Fuel 1) together with NEt3/PhCH2Br (cofuels), the transiently formed [Ag(1)]+ showed a stochastic shuttling of the silver macrocycle between two degenerate triazole stations on the thread (k298 = 1.2 × 105 s-1), whereas [Cu(2)(3)]+ was unperturbed. Instead, treatment of the mixture with PPh3 as an alternative fuel (Fuel 2) in the presence of oxidant 4 (cofuel) generated the complex [Cu(3)(PPh3)2]+ and transient thermal motion in rotor 2 (k298 = 4.9 × 104 s-1), whereas rotaxane 1 stayed dormant. Thus, two distinct chemical fuels selectively and orthogonally activated two distinct transient motion devices from a multicomponent mixture. In total, four interference-free dissipative cycles were demonstrated by using alternating fuel additions.

Concurrent tandem catalysis enabled by nanomechanical motion in heteroleptic four-component dual-catalyst machinery.

When the basic ligand 3 was added to the heteroleptic three-component slider-on-deck [Ag3(1)(2)]3+ (sliding frequency k298 = 57 kHz), it operated as a moderate brake pad (k298 = 45 kHz). Due to motion in the resulting four-component slider-on-deck [Ag3(1)(2)(3)]3+, both ligand 3 and silver(I) were continuously exposed and became catalytically active in a concurrent tandem Michael addition/hydroalkoxylation.

Fast and slow walking driven by chemical fuel.

We demonstrate the fast forward and slow backward motion of a biped on a tetrahedral track using chemical fuel, cooperative binding and kinetic selectivity. Walking of the biped is based on its dibenzyl amine feet that bind to zinc porphyrin units and, upon protonation, to dibenzo 24-crown-8 sites affording pseudorotaxane linkages.

Self-Healing of a Copper(I) [2]Rotaxane Shuttle Monitored by Fluorescence.

We demonstrate self-healing of the shuttling dynamics of a molecular machine operating by negative feedback. When zinc(II) was added to the copper(I)-loaded [2]rotaxane shuttle [Cu(R)]+, copper(I) was replaced, thereby generating the static zinc(II)-loaded [2]rotaxane [Zn(R)]2+. Loss of the dynamics was accompanied by a fluorescence enhancement at λ = 364 nm. Notably, the released copper(I) ions catalyzed the formation of a bis-triazole ligand, which selectively captured zinc(II). As a result, the copper(I) was restored in the rotaxane, and the dynamic shuttling motion of [Cu(R)]+ was regained. The healing was conveniently followed by diagnostic fluorescence changes.

Proton transfer network with luminescence display controls OFF/ON catalysis that generates a high-speed slider-on-deck.

A three-component network for OFF/ON catalysis was built from a protonated nanoswitch and a luminophore. Its activation by addition of silver(i) triggered the proton-catalyzed formation of a biped and the assembly of a fast slider-on-deck (k 298 = 540 kHz).

Dynamics of the alkyne → copper(I) interaction and its use in a heteroleptic four-component catalytic rotor.

The HETPYNE (HETeroleptic Phenanthroline and alkYNE metal) and DABCO·(zinc porphyrin)2 interactions were used to assemble the four-component nanorotor ROT-1 that exhibited a highly dynamic alkyne → copper(I) dissociation (k298 = 240 kHz) at 298 K. Quantitative click reaction transformed ROT-1 into the new rotor ROT-2 (k298 = 77 kHz) with a triazole → copper(I) linkage thus opening perspectives for bioorthogonal click strategies to biohybrid machinery.

Three-Input Logic AND Gate Drives Sequential Three-Step Catalysis by Parallel Activation of H+ and Ag+ as a Catalyst Duo.

Boolean operations with multiple catalysts as output are yet unknown using molecular logic. The issue is solved using a two-component ensemble, composed of a receptor and rotaxane, which acts as a three-input AND gate with a dual catalytic output. Actuation of the ensemble gate by the stoichiometric addition of metal ions (Ag+ and Cd2+) and 2,2,2-trifluoroacetic acid generated in the (1,1,1) truth table state a catalyst duo that synergistically enabled a three-step reaction, furnishing a dihydroisoquinoline as the output of a three-input logic AND gate operation.

Synchronizing Two Distinct Nano-Circular Sliding Motions in Six-Component Machinery for Double Catalysis.

The heteroleptic multi-component double slider-on-deck system DS3 exhibits tight coupling of motional speed of two distinct nano-circular sliders (k298 =77 and 41 kHz) despite a 2.2 nm separation. In comparison, the single sliders in DS1 and DS2 move at vastly different speed (k298 =1.1 vs. 350 kHz). Synchronization of the motions in DS3 remains even when one slows the movement of the faster slider using small molecular brake pads. In contrast to the individual DS1 and DS2 systems, DS3 is a powerful catalyst for a two-step reaction by using the motion of both sliders to drive two catalytic processes.

Potential-Dependent Adhesion Forces between dsDNA and Electroactive Surfaces.

A promising approach to regulating the interactions between polyelectrolytes and materials is the use of electroactive surfaces that can change their charge state. However, common electroactive groups are too unstable to be practical for this purpose. Here we have performed a single molecule force spectroscopy study of the interactions between dsDNA and an 1,1'-biferrocenylene (BFD = bis(fulvalene)diiron)-terminated self-assembled monolayer surface that allows us to reversibly change the charge state. We found that the interaction force between DNA and the surface is correlated to the oxidation state of the BFD groups, which is conveniently controlled by the electrochemical potentials. We discovered that the electroactive SAM produces much stronger interaction forces than its nonelectroactive counterpart. A model based on the Grahame equation was able to quantitatively reproduce the experimentally observed relation between the applied potentials and adhesion forces. Our electroactive surface provides a model system for quantitative studies of the interactions between polyelectrolyte and charged surfaces in liquid. These insights may enable new opportunities for actively manipulating the binding, orientations, and conformations of polyelectrolytes for biosensing, nanomotors, and other applications.

Parallel Allosteric Inhibition of Shuttling Motion and Catalysis in a Silver(I)-loaded [2]Rotaxane.

A dynamic silver(I)-loaded [2]rotaxane shuttle (k298 = 135 kHz) was converted allosterically into a conformationally restricted [2]rotaxane due to the creation of a bulky imine in the center of the axle component. Only the dynamic silver(I)-loaded [2]rotaxane was able to catalyze a 6-endo-cyclization reaction, whereas the static one was catalytically quiet. The mechanism of catalyst deactivation was elucidated.

Multicomponent Pseudorotaxane Quadrilateral as Dual-Way Logic AND Gate with Two Catalytic Outputs.

A multicomponent pseudorotaxane quadrilateral was reversibly toggled between three distinct switching states. Switching in the forward conversion was achieved by addition of H+ and K+ ions, and switching in the reverse direction was performed by addition of 18-crown-6 and 1-aza-18-crown-6. In both the forward and backward ways, the inputs operated an AND gate with distinct catalytic outputs. While in the forward direction the logic AND operation starting from a heteroleptic five-component assembly turned "ON" an imine hydrolysis as output (AND-1), in the inverse direction a Michael addition was ignited as the output starting from a seven-component aggregate following the AND gate logic (AND-2).

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis.

Supramolecular catalysis is reviewed with an eye on heteroleptic aggregates/complexation. Since most of the current metallosupramolecular catalytic systems are homoleptic in nature, the idea of breaking/reducing symmetry has ignited a vivid search for heteroleptic aggregates that are made up by different components. Their higher degree of functional diversity and structural heterogeneity allows, as demonstrated by Nature by the multicomponent ATP synthase motor, a more detailed and refined configuration of purposeful machinery. Furthermore, (metallo)supramolecular catalysis is shown to extend beyond the single "supramolecular unit" and to reach far into the field and concepts of systems chemistry and information science.

Catalytic machinery in motion: controlling catalysis via speed.

Three 3-component copper(I)-based slider-on-deck systems served as catalysts for a click reaction showing a higher catalytic activity with increasing sliding speed. Upon addition of brake stones, the motion of the resulting 4-component machinery was slowed and eventually stopped (on the NMR time scale) with the effect that catalysis was reduced or obstructed.

Concurrent base and silver(I) catalysis pulsed by fuel acid.

Treatment of a crown-ether receptor and a silver(I)-loaded cyclam derivative (NetState-I) with a fuel acid reversibly afforded the protonated cyclam and the silver(I)-loaded crown ether (NetState-II). While NetState-I was catalytically OFF, a base-catalysed Michael addition and a silver(I)-catalysed oxime cyclisation reaction was pulsed under dissipative conditions in NetState-II.