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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.

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.

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.

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).

In State-I, a mixture comprising a DABCO-bridged tris(zinc-porphyrin) double decker and a free biped (=slider), catalysis was OFF. Acid addition (TFA or Di-Stefano fuel acid) to State-I liberated DABCO-H+while generating a highly dynamic slider-on-deck device (State-II). The released DABCO-H+acted as a base organocatalyst for a Knoevenagel reaction (catalysis ON). The system was reversed to State-I (catalysis OFF) by reducing the acidity in the system (by adding DBU or via the fuel-derived base).

Driving conformational motion in defined off-equilibrium oscillations can be achieved using chemical fuels. When the ultrafast turnstile 1(k298> 1012Hz) was fueled with 2-cyano-2-phenylpropanoic acid (Fuel 1), the diprotonated rotor [H2(1)]2+(k298= 84.0 kHz) formed as a transient regaining the dynamics of the initial turnstile after consumption of the fuel (135 min). Upon addition of silver(I) (Fuel 2) to turnstile 1, the metastable rotor [Ag2(1)]2+(k298= 1.57 Hz) was initially furnished, but due to a consequentially triggered SN2 reaction, the Ag+ions were consumed as insoluble AgBr along with regeneration of 1(within 3 h). The off-equilibrium fast ⇆ slow rotor conversions fueled by acid and silver(I) were directly monitored by fluorescence and 1H NMR. In addition, metal ion exchange was fueled enabling off-equilibrium oscillations between rotors [Li2(1)]2+⇆ [Ag2(1)]2+. In the end, both sustainability and efficiency of the process were increased in unison by using the interfering proton waste in the formation of a [2]pseudorotaxane.

A 3-fold completive self-sorted library of dynamic motifs was integrated into the design of the pseudorotaxane-based rotor [Zn(2·H+)(3)(4)]2+operating at k298= 15.4 kHz. The rotational motion in the five-component device is based on association/dissociation of the pyridyl head of the pseudorotaxane rotator arm between two zinc(II) porphyrin stations. Addition of TFA or 2-cyano-2-phenylpropanoic acid as a chemical fuel to a zinc release system and the loose rotor components 2–4enabled the liberated zinc(II) ions and protons to act in unison, setting up the rotor through the formation of a heteroleptic zinc complex and a pseudorotaxane linkage. With chemical fuel, the dissipative system was reproducibly pulsed three times without a problem. Due to the double role of the fuel acid, two kinetically distinct processes played a role in both the out-of-equilibrium assembly and disassembly of the rotor, highlighting the complex issues in multitasking of chemical fuels.

A molecular shuttle consisting of a dibenzo-24-crown-8 macrocycle and an axle with two degenerate peripheral triazolium stations, a central dibenzyl ammonium station, and two anthracenes stoppers was exposed to 2-cyano-2-phenylpropanoic acid as a chemical fuel. Protonation/deprotonation of the amine reversibly switches the rotaxane from a static and little emissive to a dynamic fluorescent shuttling device, the latter exhibiting rapid motion (15 kHz at 25 °C). Four fuel cycles were run.

Structural characterization in on-surface synthesis is primarily carried out by Scanning Probe Microscopy (SPM) which provides high lateral resolution. Yet, important fresh perspectives on surface interactions and molecular conformations are gained from adsorption heights that remain largely inaccessible to SPM, but can be precisely measured with both elemental and chemical sensitivity by Normal-Incidence X-ray Standing Wave (NIXSW) analysis. Here, we study the evolution of adsorption heights in the on-surface synthesis and post-synthetic decoupling of porous covalent triazine–phenylene networks obtained from 2,4,6-tris(4-bromophenyl)-1,3,5-triazine (TBPT) precursors on Ag(111). Room temperature deposition of TBPT and mild annealing to ∼150 °C result in full debromination and formation of organometallic intermediates, where the monomers are linked into reticulated networks by C–Ag–C bonds. Topologically identical covalent networks comprised of triazine vertices that are interconnected by biphenyl units are obtained by a thermally activated chemical transformation of the organometallic intermediates. Exposure to iodine vapor facilitates decoupling by intercalation of an iodine monolayer between the covalent networks and the Ag(111) surface. Accordingly, Scanning Tunneling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and NIXSW experiments are carried out for three successive sample stages: organometallic intermediates, covalent networks directly on Ag(111) and after decoupling. NIXSW analysis facilitates the determination of adsorption heights of chemically distinct carbon species, i.e.in the phenyl and triazine rings, and also for the organometallic carbon atoms. Thereby, molecular conformations are assessed for each sample stage. The interpretation of experimental results is informed by Density Functional Theory (DFT) calculations, providing a consistent picture of adsorption heights and molecular deformations in the networks that result from the interplay between steric hindrance and surface interactions. Quantitative adsorption heights, i.e.vertical distances between adsorbates and surface, provide detailed insight into surface interactions, but are underexplored in on-surface synthesis. In particular, the direct comparison with an in situprepared decoupled state unveils the surface influence on the network structure, and shows that iodine intercalation is a powerful decoupling strategy.

The present work demonstrates the operation of a reversible supramolecular gate, i.e., an ensemble of various components linked by chemical communication, which is triggered by stoichiometric chemical inputs and by obeying the AND truth table delivers a stoichiometric chemical signal. The output triggers a series of events that finally set up a catalytic process. In detail, a three-component AND gate, composed of two distinct nanoswitches, a copper-loaded and an unloaded one {= state (0,0)}, was actuated with stoichiometric amounts of two inputs (IN-1= Zn2+, IN-2= Hg2+) generating copper(I) ions as output in state (1,1). The utility of this information processing was highlighted by using the copper(I) output for triggering the self-assembly of the four-component rotor ROT-2through metal translocation. In the presence of suitable reactants, ROT-2acted as a catalytic machinery catalyzing a click reaction (= signal amplification). Verification of the functioning of the AND gate in a mixture of 12 components was thus accomplished by monitoring formation of the click product. Due to the stoichiometric design, the gate was reset to state (0,0) by adding hexacyclen and reactivated by adding inputs IN-1and IN-2alike in the first cycle.

The present paper adds the time domain to chemical ion translocation and (supra)molecular logic. When the self-sorted system of [Zn(1)]2++ [Li(2)]++ 3(composed of hexacyclen 1, nanoswitch 2, luminophore 3) was treated with 2-cyano-2-phenylpropanoic acid (4) as a chemical fuel, protonation of 1entailed a cascade translocation of first Zn2+, then Li+, resulting in the system [H(1)]++ [Zn(2)]2++ [Li(3)]+that slowly reversed back to the initial state. The kinetic evolution of the lithium pulses was followed by changes in color and luminescence using the lithium-sensitive probe 3. The utility of fueling in combination with lithium pulses was exemplified among others by generating time-encoded SOS morse signals and implementing the time domain in two distinct AND gates.

Different from the current paradigms of chemistry, a switchable catalytic system is presented that does not rely on a molecular switch in different toggling states but on a smart seven-component mixture that manages the reversible ON/OFF regulation of two catalytic processes. Hereunto, the workflow of two multicomponent rotary catalytic machineries was interlinked by the simultaneous shuffling of two components (metal and ligand) requiring perfect signaling in a 13-component system (see Movie 1). This network underwent reversible switching over three cycles as demonstrated by 1H NMR, UV–vis, and fluorescence spectroscopies and electrospray ionization mass spectrometry. Addition and removal of zinc(II) ions trigger three distinct events in parallel: the (i) mutually dependent self-assembly of three-component nanorotors and two-component reservoirs by resorting components, (ii) toggling between vastly different rotational exchange rates in the self-assembled rotors that directly affect catalysis, and (iii) toggling between two diverse catalytic reactions in a fully reproducible manner. Because of this information system, the concentrations of free aza-crown ether 7and its complex with copper(I), that is, [Cu(7)]+, which represent the effective catalysts, are up- and downregulated in a manner to alternately switch ON/OFF a catalytic conjugate addition and a click reaction.

The silver(I) catch–release system composed of nanoswitch 1and the anthracene-appended crown ether 2is infallibly driven by chemical triggers and ion transfer. Any state of the silver(I) translocation is self-reported by a ratiometric emission signature at 472 and 554 nm. In the self-sorted networked state I, the silver(I) ions are tightly shielded inside nanoswitch [Ag(1)]+(“catch”) so that their catalytic activity is zero while emission at 554 nm is maximum. Addition of zinc(II) releases silver(I) from [Ag(1)]+and generates the catalytically active and fluorescent complex [Ag(2)]+. In this networked state II (“release”) both catalytic activity and emission at 472 nm are maximum. Removal of the original trigger regenerates networked state I. ON/OFF control and recycling of catalyst was demonstrated over three in situcycles.

The self-assembled cage ROT-1was prepared from the pyridine-terminated rotator 1, the phenanthroline-appended stator 2, DABCO, and copper(I) ions in a ratio of 1:1:1:4. This four-component assembly is held together by two pyridine→[Cu(phenAr2)]+as well as two DABCO→zinc porphyrin interactions (phenAr2= 2,9-diarylphenanthroline) and does not show any motion on the NMR time scale (k< 0.1 s–1, 298 K). However, it is converted to the fast nanorotor ROT-1xCD3CNby addition of CD3CN [x= (v/v)% of acetonitrile in dichloromethane] due to acceleration of both pyridine→copper(I) dissociation steps. Now the rotator is able to visit all four copper(I)-loaded phenanthroline stations of the stator. Depending on the amount of CD3CN, the exchange frequency of the nanorotor varies from 0.7 s–1(CD3CN:CD2Cl2= 1:29) to 8000 s–1(CD3CN:CD2Cl2= 1:5) at 25 °C. When iodide (I–) is added to the static assembly ROT-1, the rotational speed increases even more drastically (k= 20 000 s–1), again due to accelerating the rate-determining pyridine→copper(I) dissociation step. In both cases, a sigmoidal relationship is established between exchange frequency and the concentration of added nucleophile (CD3CN or iodide) that suggests the presence of a cooperative effect. Reversible switching between the static assembly and fast rotor was performed several times without any decomposition of the system. In contrast, addition of the common nucleophile PPh3to ROT-1does not increase the rotational speed, a finding that is explained on thermodynamic grounds.

Three-component nanorotor R1(k298= 80 kHz) and two-component slider-on-deck DS2(k298= 440 kHz) were prepared from rotator S1and stator [Cu3(1)]3+and from S2and deck D, respectively. Mixing of R1with DS2leads to clean metathesis, furnishing the slower nanodevices R2(k298= 29.6 kHz) and DS1(k298= 32.2 kHz). Exchange of the piston rods S1and S2is completed within 22 min (uncatalyzed) or 3 min (catalyzed) at 298 K.

Three distinct four-component supramolecular nanorotors, prepared by varying the rotator’s structure and keeping all other components constant, exhibit rotational frequencies that differ by almost 2 orders of magnitude. When the rotors were used as catalyst for two click reactions, the product yield correlated with the speed of the machine, e.g., 20% at 0.50 kHz, 44% at 20 kHz and 62% at 42 kHz. The kinetic effect on the product yield is attributed to the ability of the rotating catalysts to displace the product more efficiently from the active site at higher speed (anchimeric assistance). This mechanistic hypothesis was convincingly corroborated by a linear correlation between product yield and product liberation.

A three-component supramolecular walker system is presented where a two-footed ligand (biped) walks back and forth on a tetrahedral 3D track upon the addition and removal of copper(I) ions, respectively. The addition of N-methylpyrrolidine as a catalyst to the walker system generates a four-component catalytic machinery, which acts as a three-state switchable catalytic ensemble in the presence of substrates for a conjugate addition. The copper(I)-ion-initiated walking process of the biped ligand on the track regulates the catalytic activity in three steps: ON versus intON (intermediate ON) versus OFF. To establish the operation of the four-component catalytic machinery in a mixture of all constituents, forward and backward cycles were performed in situ illustrating that both the walking process and catalytic action are fully reversible and reproducible.

Four-component nanorotors are prepared by the self-assembly of stator [Cu4(4)]4+with its four copper(I)-loaded phenanthroline stations and various rotators carrying one, two, or three pyridine terminals. The fourth component, 1,4-diazabicyclo[2.2.2]octane, serves as a connecting axle between rotator and stator. Capitalizing on the heteroleptic pyridyl and phenanthroline metal complexes concept, the rotator’s pyridine terminals are connected to the copper(I)-loaded phenanthroline stations (Npy→ [Cu(phen)]+) in the STOP state and disconnected in the transition state of rotation. As the barrier of the thermally activated rotation, measured by variable-temperature 1H NMR, is mainly governed by attractive forces between stator stations and rotator terminals, it increases along the series Ea(monopyridine rotator) < Ea(dipyridine rotator) < Ea(tripyridine rotator). However, there are even distinct differences in rate between rotors with equal number of rotator terminals. The change from the 5,10-dipyridyl (cis) to 5,15-dipyridyl (trans) zinc porphyrin rotator enhances the rotational frequency by almost 1000-fold. Density functional theory computational results suggest that not only coordinative Npy→ [Cu(phen)]+interactions but also dispersive attraction influence the barrier of rotation.

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 1and turnstile [Cu(2)(3)]+was charged with AgBF4as 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 × 105s–1), whereas [Cu(2)(3)]+was unperturbed. Instead, treatment of the mixture with PPh3as 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 × 104s–1), whereas rotaxane 1stayed 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.

Self-assembly of 1,3,5-tris(4-mercaptophenyl)benzene (TMB), a 3-fold symmetric, thiol-functionalized aromatic molecule, was studied on Au(111) with the aim of realizing extended Au–thiolate-linked molecular architectures. The focus lay on resolving thermally activated structural and chemical changes by a combination of microscopy and spectroscopy. Thus, scanning tunneling microscopy (STM) provided submolecularly resolved structural information, while the chemical state of sulfur was assessed by X-ray photoelectron spectroscopy (XPS). Directly after room-temperature deposition, only less well ordered structures were observed. Mild annealing promoted the first structural transition into ordered molecular chains, partly organized in homochiral molecular braids. Further annealing led to self-similar Sierpiński triangles, while annealing at even higher temperatures again resulted in mostly disordered structures. Both the irregular aggregates observed at room temperature and the chains were identified as metal–organic assemblies, whereby two out of the three intermolecular binding motifs are energetically equivalent according to density functional theory (DFT) simulations. The emergence of Sierpiński triangles is driven by a chemical transformation, i.e., the conversion of coordinative Au–thiolate to covalent thioether linkages, and can be further understood by Monte Carlo simulations. The great structural variance of TMB on Au(111) can on one hand be explained by the energetic equivalence of two binding motifs. On the other hand, the unexpected chemical transition even enhances the structural variance and results in thiol-derived covalent molecular architectures.

Herein, we demonstrate how the supramolecular complexity (evaluated by the degree of self-sorting M) evolves in a chemical cycle of cascaded metallosupramolecular transformations, using abiological self-assembled entities as input signals. Specifically, the successive addition of the supramolecular self-assembled structures S1and (T2+ S2) to the starting supramolecular two-component equilateral triangle T1(M= 1) first induced a fusion into the three-component quadrilateral R1(M= 6) and then to the five-component scalene triangle T3(M= 16). Upon the addition of the supramolecular input M1to T3, a notable self-sorting event occurred, leading to regeneration of the triangle T1along with formation of the scalene triangle T4(M= 25). This last step closed the cycle of the supramolecular transformations.