From Beam Damage to Massive Reaction Amplification under the Electron Microscope: An Ionization-Induced Chain Reaction in Crystals of a Dewar Benzene.

Electron microscopy in its various forms is one of the most powerful imaging and structural elucidation methods in nanotechnology where sample information is generally limited by random chemical and structural damage. Here we show how a well-selected chemical probe can be used to transform indiscriminate chemical damage into clean chemical processes that can be used to characterize some aspects of the interactions between high-energy electron beams and soft organic matter. Crystals of a Dewar benzene exposed to a 300 keV electron beam facilitate a clean valence-bond isomerization radical-cation chain reaction where the number of chemical events per incident electron is amplified by a factor of up to ca.

Networked Multicomponent Ensemble as AND Gate with FRET Output.

A networked supramolecular logic AND gate system is accomplished using precise chemical communication within a multicomponent ensemble via metal ion-driven self-sorting processes. The cybernetic AND gate is composed of a copper(I)-loaded nanoswitch, an aza-crown ether and a rhodamine receptor. The modus operandi of the AND gate, from state (0,0), was induced with stoichiometric amounts of two inputs (IN-1=Hg, IN-2=Li) generating copper(I) ions as output only in state (1,1).

Cascade Photoreaction in Crystals: A Phase Change Caused by a Dewar Benzene Quantum Chain Triggers a Topochemical [2 + 2] Photodimerization.

Crystals undergoing tandem reactions where the first transformation enables the second one are rare. Using photoreactive Dewar benzene 3,4,5,6-tetramethyl-1,2-dicarboxylic diacid () as a hydrogen-bonding template for the [2π+2π] photodimerization of -4,4'-bipyridyl-ethenes (), we obtained crystals with a = 2:1 stoichiometry with double bonds at a nonreactive distance of 5.957 Å.

Dynamic negative allosteric effect: regulation of catalysis 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.

Reaction amplification with a gain: Triplet exciton-mediated quantum chain using mixed crystals with a tailor-made triplet sensitizer.

Photochemical valence bond isomerization of a crystalline Dewar benzene () diacid monoanion salt with an acetophenone-linked piperazinium cation that serves as an intramolecular triplet energy sensitizer () exhibits a quantum chain reaction with as many as 450 product molecules per photon absorbed (Φ ≈ 450). By contrast, isomorphous crystals of the diacid monosalt of an ethylbenzene-linked piperazinium () lacking a triplet sensitizer showed a less impressive quantum yield of ca. Φ ≈ 22.

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

When the slider-on-deck [Cu(1)(2)] and guest G were treated with palladium(II) ions, the biped 2 was released from [Cu(1)(2)] generating the nanocage [Pd(2)(G)] 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, Ca 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 Ca ions as inputs.

Quantum chain amplification in nanocrystalline Dewar benzenes by intramolecular sensitization.

Quantum chain reactions are characterized by the formation of several photoproducts per photon absorbed ( > 1) and constitute a promising signal amplification mechanism. The triplet-sensitized isomerization of Dewar benzene is known to undergo quantum chain reactions characterized by an adiabatic valence-bond isomerization to the excited state of Hückel benzene, which is able to transfer its triplet energy to a new ground state Dewar benzene that reacts to continue the chain. Given that diffusion-mediated energy transfer is the chain-limiting event in solution, we demonstrate here that reactions in crystals are significantly more efficient by taking advantage of energy transfer by a presumed exciton delocalization mechanism.

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.

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.

Fuel Acid Drives Base Catalysis and Supramolecular Cage-to-Device Transformation under Dissipative Conditions.

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).

Cooperative Effects in Switchable Catalysis: Enhancing Double-Click Reaction Yield of Symmetrical Rotaxanes.

Reversible switching between the closed cyclic dimeric assembly [Cu (1) ] (OFF state) and the extended dimeric homoleptic complex [FeCu (1) ] (ON State) by addition/removal of Fe triggered catalysis of a double-click reaction and high yield preparation of [2]rotaxanes. Mechanistic and computational studies provide valuable general insight for double-click strategies by revealing cooperative effects in the second cycloaddition step due to a distance-tolerant preorganization of the first-click product by the two copper(I)-loaded phenanthroline subunits of [FeCu (1) ] .

Evolution of catalytic machinery: three-component nanorotor catalyzes formation of four-component catalytic machinery.

The three-component nanorotor [Cu2(S)(R)]2+ (k298 = 46.0 kHz) that is a catalyst for a CuAAC reaction binds the click product at each of its copper centers thereby creating a new platform and a dynamic slider-on-deck system. Due to this sliding motion (k298 = 65.

Multitasking with Chemical Fuel: Dissipative Formation of a Pseudorotaxane Rotor from Five Distinct Components.

A 3-fold completive self-sorted library of dynamic motifs was integrated into the design of the pseudorotaxane-based rotor [Zn(·H)()()] operating at = 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.

Interaction and thermal stability of carboxymethyl cellulose on α-FeO(001) surface: ReaxFF molecular dynamics simulations study.

Reactive (ReaxFF) molecular dynamic simulations were performed to elucidate the nature of interaction between hematite and carboxymethyl cellulose (CMC) considering effect of moisture and temperature. Simulations showed that the presence of moisture prohibited CMC to interact directly with hematite surface. However, the moisture helps to disperse CMC along the hematite surface thus maximizing the interaction.

Reversible switching from a three- to a nine-fold degenerate dynamic slider-on-deck through catenation.

Two dynamic slider-on-deck assemblies, i.e. a two-component threefold degenerate (k298 = 34.

Remote Control of the Synthesis of a [2]Rotaxane and its Shuttling via Metal-Ion Translocation.

Remote control in an eight-component network commanded both the synthesis and shuttling of a [2]rotaxane via metal-ion translocation, the latter being easily monitored by distinct colorimetric and fluorimetric signals. Addition of zinc(II) ions to the red colored copper-ion relay station rapidly liberated copper(I) ions and afforded the corresponding zinc complex that was visualized by a bright sky blue fluorescence at 460 nm. In a mixture of all eight components of the network, the liberated copper(I) ions were translocated to a macrocycle that catalyzed formation of a rotaxane by a double-click reaction of acetylenic and diazide compounds.

Selective and reversible interconversion of nanosliders commanded by remote control via metal-ion signaling.

A multi-device network mainly consisting of two two-component nanosliders was formed by self-sorting of six components. Addition/removal of zinc(ii) ions reversibly reorganized the network by chemical signaling involving the translocation of copper(i) from a relay station followed by the selective disassembly/assembly of one of both multi-component devices. The thus liberated machine parts served to erect a three-component nanoslider alongside the other unchanged two-component nanoslider.

Time-Dependent Pulses of Lithium Ions in Cascaded Signaling and Out-of-Equilibrium (Supra)molecular Logic.

The present paper adds the time domain to chemical ion translocation and (supra)molecular logic. When the self-sorted system of [Zn()] + [Li()] + (composed of hexacyclen , nanoswitch , luminophore ) was treated with 2-cyano-2-phenylpropanoic acid () as a chemical fuel, protonation of entailed a cascade translocation of first Zn, then Li, resulting in the system [H()] + [Zn()] + [Li()] 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 .

Selective detection of DABCO using a supramolecular interconversion as fluorescence reporter.

The quantitative double self-sorting between the three-component rectangle [Cu()()] and the four-component sandwich complex [Cu()()()] is triggered by inclusion and release of DABCO (). The fully reversible and clean switching between two multicomponent supramolecular architectures can be monitored by fluorescence changes at the zinc porphyrin sites. The structural changes are accompanied by a huge spatial contraction/expansion of the zinc porphyrin-zinc porphyrin distances that change from 31.

Cation exchange reversibly switches rotor speed and is monitored by a networked fluorescent reporter.

Framework 1, a freely rotating turnstile, is transformed by sequential metal ion addition into the coordination-based double-minimum rotors [M2(1)]2n+ that operate at 8 kHz (M = Zn2+; n = 2) and 30 kHz (M = Cu+; n = 1). In a network with the fluorescent receptor 2, the metal ion exchange at [M2(1)]2n+ and thus indirectly the rotor speed is reported by distinct fluorescence changes at 2.

Catch-Release System for Dosing and Recycling Silver(I) Catalyst with Status of Catalytic Activity Reported by Fluorescence.

The silver(I) catch-release system composed of nanoswitch 1 and the anthracene-appended crown ether 2 is 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.

Machine Metathesis: Thermal and Catalyzed Exchange of Piston Rods in Multicomponent Nanorotor/Nanoslider Ensemble.

Three-component nanorotor R1 ( k = 80 kHz) and two-component slider-on-deck DS2 ( k = 440 kHz) were prepared from rotator S1 and stator [Cu(1)] and from S2 and deck D, respectively. Mixing of R1 with DS2 leads to clean metathesis, furnishing the slower nanodevices R2 ( k = 29.6 kHz) and DS1 ( k = 32.

Oscillating Emission of [2]Rotaxane Driven by Chemical Fuel.

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.

Catalytic Three-Component Machinery: Control of Catalytic Activity by Machine Speed.

Three supramolecular slider-on-deck systems DS1-DS3 were obtained as two-component aggregates from the sliders S1-S3 and deck D with its three zinc porphyrin (ZnPor) binding sites. The binding of the two-footed slider to the deck varies with the donor qualities of and the steric hindrance at the pyridine/pyrimidine (pyr) feet, and was effected by two N →ZnPor interactions. Accordingly, the sliders move over the three zinc porphyrins in the deck at different speeds, namely with 32.