Optical‐Dielectric Duple Bistable Switches: Photoluminescence of Reversible Phase Transition Molecular Material

Molecular optical‐dielectric duple bistable switches are photoelectric (dielectric and fluorescent) multifunctional materials that can simultaneously convert optical and electrical signals in one device for seamless integration. However, exploring optical‐dielectric duple channels of dielectric and photoluminescence is still a bigger challenge than single dielectric or photoluminescence bistable ones, which are hardly reported but probably will be heavily researched owing to the new generation artificial intelligence development needs in the future. Herein, a new optical‐dielectric duple bistable switches material, [(CH₃)₃NCH₂CH₃]₂MnCl₄ ( I ), was obtained by a simple method for volatilization of solvents. Variable temperature single crystal X‐ray analysis indicates that material I has a reversible bistable structure (order‐disorder structure phase transition) corresponding to switching “ON′′ and ”OFF′′. Unlike the single dielectric bistable structures that were previously reported, material I also own bistable features in terms of fluorescence property. This material enriches the specific examples of photoelectric duple function switch materials and facilitates the development of required devices.     

Switchable Dielectric Phase Transition Triggered by Pendulum‐Like Motion in an Ionic Co‐crystal

Molecular‐based ionic co‐crystals, which have the merits of low‐cost/easy fabrication processes and flexible structure and functionality, have already exhibited tremendous potential in molecular memory switches and other electric devices. However, dipole (ON/OFF switching) triggering is a huge challenge. Here, we introduce a pendulum‐like dynamic strategy to induce the order–disorder transition of a co‐crystal [C₅H₇N₃Cl]₃[Sb₂Br₉] (compound 1 ). Here, the anion and cation act as a stator and a pendulum‐like rotor (the source of the dielectric switch), respectively. The temperature‐dependent dielectric and differential scanning calorimetry (DSC) analyses reveal that 1 undergoes a reversible phase transition, which stems from the order–disorder transition of the cations. The thermal ON/OFF switchable motions make 1 a promising candidate to promote the development of bulk crystals as artificial intelligent dielectric materials. In addition, the pendulum‐like molecular dynamics and distinct arrangements of two coexisting ions with a notable offset effect promotes/hinders dipolar reorientation after dielectric transition and provides a rarely observed but fairly useful and feasible strategy for understanding and modulating the dipole motion in crystalline electrically polarizable materials.     

In Situ Synthesis and Nonvolatile Rewritable‐Memory Effect of Polyaniline‐Functionalized Graphene Oxide

A new polyaniline (PANI)‐functionalized graphene oxide (GO‐PANI) was prepared by using an in situ oxidative graft polymerization of aniline on the surface of GO. Its highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), ionization potential (IP), and electron affinity (EA) values experimentally estimated by the onset of the redox potentials were ?5.33, ?3.57, 5.59, and 3.83 eV, respectively. A bistable electrical‐switching effect was observed in electronic device with the GO‐PANI film sandwiched between the indium tin oxide (ITO) and Al electrodes. This device exhibited two accessible conductivity states, that is, the low‐conductivity (OFF) state and the high‐conductivity (ON) state, and can be switched to the ON state under a negative electrical sweep, and can also be reset to the initial OFF state by a reverse (positive) electrical sweep. The ON state is nonvolatile and can withstand a constant voltage stress of ?1 V for 3 h and 10⁸ read cycles at ?1 V under ambient conditions. The nonvolatile nature of the ON state and the ability to write, read, and erase the electrical states, fulfill the functionality of a rewritable memory. An ON/OFF current ratio of more than 10⁴ at ?1 V achieved in this memory device is high enough to promise a low misreading rate through the precise control of the ON and OFF states. The mechanism associated with the memory effects was elucidated from molecular simulation results.     

A Solution‐Processable Donor–Acceptor Compound Containing Boron(III) Centers for Small‐Molecule‐Based High‐Performance Ternary Electronic Memory Devices

A novel small‐molecule boron(III)‐containing donor–acceptor compound has been synthesized and employed in the fabrication of solution‐processable electronic resistive memory devices. High ternary memory performances with low turn‐on (V_Th1=2.0 V) and distinct threshold voltages (V_Th2=3.3 V), small reading bias (1.0 V), and long retention time (>10⁴ seconds) with a large ON/OFF ratio of each state (current ratio of “OFF”, “ON1”, and “ON2”=1:10³:10⁶) have been demonstrated, suggestive of its potential application in high‐density data storage. The present design strategy provides new insight in the future design of memory devices with multi‐level transition states.     

A Toggle Nanoswitch Alternately Controlling Two Catalytic Reactions

Reversible switching between two states of the triangular nanoswitch [Cu( 1 )]⁺ was accomplished by alternate addition of 2‐ferrocenyl‐1,10‐phenanthroline ( 2 ) and copper(I) ions. The two switching states regulate the binding and release of two distinct catalysts, piperidine and [Cu( 2 )]⁺, in a fully interference‐free manner and allow alternating on/off switching of two orthogonal catalytic processes. In switching state I, piperidine is released from the nanoswitch and catalyzes a Knoevenagel addition between 4‐nitrobenzaldehyde and diethyl malonate (ON‐1 and OFF‐2), while in state II the released [Cu( 2 )]⁺ catalyzes a click reaction between 4‐nitrophenylacetylene and benzylazide (OFF‐1 and ON‐2). Upon addition of one equivalent of 2 to the (OFF‐1 and ON‐2)‐state, both catalytically active processes are shut down (OFF‐1 and OFF‐2).     

Ternary Conductance Switching Realized by a Pillar[5]arene-Functionalized Two-Dimensional Imine Polymer Film

Nowadays, most manufacturing memory devices are based on materials with electrical bistability (i. e., “0” and “1”) in response to an applied electric field. Memory devices with multilevel states are highly desired so as to produce high-density and efficient memory devices. Herein, we report the first multichannel strategy to realize a ternary-state memristor. We make use of the intrinsic sub-nanometer channel of pillar[5]arene and nanometer channel of a two-dimensional imine polymer to construct an active layer with multilevel channels for ternary memory devices. Low threshold voltage, long retention time, clearly distinguishable resistance states, high ON/OFF ratio (OFF/ON1/ON2=1 : 10 : 10³), and high ternary yield (75 %) were obtained. In addition, the flexible memory device based on 2DP_TPAZ+TAPB can maintain its stable ternary memory performance after being bent 500 times. The device also exhibits excellent thermal stability and can tolerate a temperature as high as 300 °C. It is envisioned that the results of this work will open up possibilities for multistate, flexible resistive memories with good thermal stability and low energy consumption, and broaden the application of pillar[n]arene.     

High hopes: can molecular electronics realise its potential?

Manipulating and controlling the self-organisation of small collections of molecules, as an alternative to investigating individual molecules, has motivated researchers bent on processing and storing information in molecular electronic devices (MEDs). Although numerous ingenious examples of single-molecule devices have provided fundamental insights into their molecular electronic properties, MEDs incorporating hundreds to thousands of molecules trapped between wires in two-dimensional arrays within crossbar architectures offer a glimmer of hope for molecular memory applications. In this critical review, we focus attention on the collective behaviour of switchable mechanically interlocked molecules (MIMs)--specifically, bistable rotaxanes and catenanes--which exhibit reset lifetimes between their ON and OFF states ranging from seconds in solution to hours in crossbar devices. When these switchable MIMs are introduced into high viscosity polymer matrices, or self-assembled as monolayers onto metal surfaces, both in the form of nanoparticles and flat electrodes, or organised as tightly packed islands of hundreds and thousands of molecules sandwiched between two electrodes, the thermodynamics which characterise their switching remain approximately constant while the kinetics associated with their reset follow an intuitively predictable trend--that is, fast when they are free in solution and sluggish when they are constrained within closely packed monolayers. The importance of seamless interactions and constant feedback between the makers, the measurers and the modellers in establishing the structure-property relationships in these integrated functioning systems cannot be stressed enough as rationalising the many different factors that impact device performance becomes more and more demanding. The choice of electrodes, as well as the self-organised superstructures of the monolayers of switchable MIMs employed in the molecular switch tunnel junctions (MSTJs) associated with the crossbars of these MEDs, have a profound influence on device operation and performance. It is now clear, after much investigation, that a distinction should be drawn between two types of switching that can be elicited from MSTJs. One affords small ON/OFF ratios and is a direct consequence of the switching in bistable MIMs that leads to a relatively small remnant molecular signature--an activated chemical process. The other leads to a very much larger signature and ON/OFF ratios resulting from physical or chemical changes in the electrodes themselves. Control experiments with various compounds, including degenerate catenanes and free dumbbells, which cannot and do not switch, are crucial in establishing the authenticity of the small ON/OFF ratios and remnant molecular signatures produced by bistable MIMs. Moreover, experiments conducted on monolayers in MSTJs of molecules designed to switch and molecules designed not to switch have been probed directly by spectroscopic and other means in support of MEDs that store information through switching collections of bistable MIMs contained in arrays of MSTJs. In the quest for the next generation of MEDs, it is likely that monolayers of bistable MIMs will be replaced by robust crystalline extended structures wherein the switchable components, derived from bistable MIMs, are organised precisely in a periodic manner.     

Nonvolatile rewritable memory effects in graphene oxide functionalized by conjugated polymer containing fluorene and carbazole units

A new polymer, poly[{9,9-di(triphenylamine)fluorene}(9,9-dihexylfluorene)(4-aminophenylcarbazole)] (PFCz) was synthesized and used in a reaction with graphene oxide (GO) containing surface-bonded acyl chloride moieties to give a soluble GO-based polymer material GO-PFCz. A bistable electrical switching effect was observed in an electronic device in which the GO-PFCz film was sandwiched between indium-tin oxide (ITO) and Al electrodes. This device exhibited two accessible conductivity states, that is, a low-conductivity (OFF) state and a high-conductivity (ON) state, and can be switched to the ON state under a negative electrical sweep; it can also be reset to the initial OFF state by a reverse (positive) electrical sweep. The ON state is nonvolatile and can withstand a constant voltage stress of -1 V for 3 h and 10(8) read cycles at -1 V under ambient conditions. The nonvolatile nature of the ON state and the ability to write, read, and erase the electrical states, fulfill the functionality of a rewritable memory. The mechanism associated with the memory effects was elucidated from molecular simulation results and in-situ photoluminescence spectra of the GO-PFCz film under different electrical biases.     

Enhanced ternary memory performances with high-temperature tolerance in AIE@PBI composites by tuning the azobenzol substituents on tetraphenylethylene

The design of functional composites with desired film crystallinity and definite switching mechanism is the key to achieve high performance multilevel memorizers. Three aggregation-induced emission (AIE) molecules containing different azobenzol (Azo) groups on tetraphenylethylene (TPE) were synthesized and embedded into polybenzimidazole (PBI) to prepare AIE@PBI composites, which were further fabricated as FTO/TPE-Azo-n@PBI/Ag (n = 01, 02, 04) devices with well-defined crystalline characteristics. These devices can demonstrate clear ternary memory performances, among which TPE-Azo-04@PBI-based one exhibited the best performance with the current ratio of 1:10^4.2:10^6.7 for “OFF”, “ON1”, and “ON2” states. The ternary memory mechanism can be designed as the combination of aggregation-induced current/conductance (AIC) and packing conformational change-induced charge transfer in TPE-Azo-n, which were verified by UV–Vis, in-situ XRD, and single-crystal structural determinations and theoretical calculations. The trend of ternary memory performance improved by increasing Azo groups on TPE can be attributed to the larger steric hindrance due to the more Azo groups, which can inhibit their aggregations and packing conformational change in PBI-confined space. Specially, this kind of devices can present high-temperature tolerance of 350 ^°C. The verified mechanism in this work might provide a practicable model for the design of new high-density memorizers with good environmental tolerance. The current ratio of OFF/ON1/ON2 increases with the Azo.     

Low-Pressure Plasma Polymerization of Acetylene–Ammonia Mixtures for Biomedical Applications

Past research in this laboratory has focused on the deposition of nitrogen- (N)-rich thin organic coatings for biomedical applications; among usual fabrication methods are plasma polymerization (PP) at low- (“L”) or atmospheric- (high-, “H”)-pressure. In the “L” case, ethylene (“E”, C₂H₄)/ammonia (NH₃) feed-gas mixtures with different flow ratios, R, are used, by which the nitrogen- and primary amine concentrations, [N] and [–NH₂], respectively, can be reproducibly controlled. The generic symbol we use for that family of deposits is L-PPE:N. In the present research, we used acetylene (“A”, C₂H₂) as the hydrocarbon feed, because our earlier experience with “H”-type materials (H-PPE:N and H-PPA:N) revealed striking differences in physico-chemical (e.g. [N] and [–NH₂], and solubility) characteristics, which are important for applications. We now find that such differences also exist between the L-PPA:N and L-PPE:N families of coatings. This is attributed to the fundamentally different bonding structures of “A” and “E”, namely CH≡CH and CH₂=CH₂; the former leads to more highly cross-linked, [NH₂]-leaner deposits, as was also noted for the “H”-type deposits mentioned above.     

NBS‐Promoted Rearrangement of 1,1‐Diarylmethylenecyclopentane

The 1‐aroyl‐1‐aryl‐2‐bromocyclopentanes 3a , 3b , 3c and 3d (Ar = C₆H₅, 2‐FC₆H₄, 3‐FC₆H₄, 4‐FC₆H₄) were prepared from N‐bromosuccinimide (NBS)‐promoted rearrangement of 1,1‐diarylmethylenecyclopentane 2 . The possible mechanism was proposed. Two 1‐phenyl‐cyclopentane carbamides 5a and 5b with the anti‐influenza effect were also accomplished from compound 3a .     

Switchable Enzyme/DNAzyme Cascades by the Reconfiguration of DNA Nanostructures

Mimicking cellular transformations and signal transduction pathways by means of biocatalytic cascades proceeding in organized media is a scientific challenge. We describe two DNA machines that enable the “ON/OFF” switchable activation and deactivation of three‐component biocatalytic cascades. One system consists of a reconfigurable DNA tweezers‐type structure, whereas in the second system the catalytic cascade proceeds on a switchable DNA clamp scaffold. The three‐component catalytic cascades consist of β‐galactosidase (β‐Gal), glucose oxidase (GOx), and the K⁺‐ion‐stabilized hemin‐G‐quadruplex horseradish peroxidase (HRP)‐mimicking DNAzyme. The hemin‐G‐quadruplex‐bridged closed structure of the tweezers or clamp allows the biocatalytic cascades to operate (switched “ON′′), whereas separation of the hemin‐G‐quadruplex by means of 18‐crown‐6‐ether opens the tweezers/clamp structures, thus blocking the catalytic cascade (switched ”OFF“). This study is complemented by two‐component, switchable biocatalytic cascades composed of GOx and hemin‐G‐quadruplex assembled on hairpin‐bridged DNA tweezers or clamp nanostructures.     

Mono‐ and Perfluoroaryliodine(III) Cyano Compounds – Synthesis,Reactivity, and Structure

C₆F₅I(CN)₂ and x‐FC₆H₄I(CN)₂ (x = 2, 3, 4) were isolated from reactions of the corresponding aryliodine difluorides ArIF₂ and a stoichiometric excess of Me₃SiCN in CCl₃F (0 °C) or CH₂Cl₂ (20 °C), respectively. In addition, x‐FC₆H₄I(CN)₂ compounds were synthesized in good yields on alternative routes, namely from 3‐ or 4‐FC₆H₄I(OC(O)CH₃)₂ or 4‐FC₆H₄I(OC(O)CF₃)₂ or from 4‐FC₆H₄IO and Me₃SiCN in CH₂Cl₂ at 20 °C. In the 1 : 1 reaction of C₆F₅IF₂ and Me₃SiCN a lower temperature was necessary to suppress partial disubstitution and to obtain the first example of a new type of aryliodine(III) cyanide compounds, C₆F₅I(CN)F. 4‐FC₆H₄I(CN)F could be isolated from the equimolar reaction of 4‐FC₆H₄IF₂ and Me₃SiCN in CH₂Cl₂ even at 20 °C. The new products were characterized by multi‐NMR and Raman spectroscopy. The molecular structures of C₆F₅I(CN)₂, 3‐ and 4‐FC₆H₄I(CN)₂, C₆F₅I(CN)F, and 4‐FC₆H₄I(CN)F are discussed and compared with that of C₆F₅IF₂. The reactivity of C₆F₅I(CN)F towards fluoride acceptors EF_n (BF₃, AsF₅) and R_xEX_?x (C₆F₅SiF₃, C₆H₅SiF₃, C₆H₅PF₄, Me₃SiCl, Me₃SiC₆F₅) were investigated and showed differing reaction patterns (fluoride abstraction, aryl transfer, chloride transfer). Besides the molecular entities C₆F₅I(CN)F and C₆F₅I(CN)Cl, the corresponding iodonium salts [C₆F₅(CN)I][BF₄] and [C₆F₅(CN)I][AsF₆] were isolated. The thermal stability of ArI(CN)₂ and ArI(CN)F, neat and in solution, as well as the reactivity of 4‐FC₆H₄I(CN)₂ towards the Lewis acid BF₃ are reported.     

Plasma- and vacuum-ultraviolet (VUV) photo-polymerisation of N- and O-rich thin films

Nitrogen (N)- and oxygen (O)-rich organic thin films were deposited by vacuum-ultraviolet (VUV)-assisted photo-chemical polymerisation of flowing ethylene (C₂H₄)–ammonia (NH₃) and C₂H₄–nitrous oxide (N₂O) mixtures of varying ratios, R, respectively. The reaction mechanism of these binary gas mixtures was investigated as a function of the wavelength, λ, of two near-mono-chromatic VUV sources. Surface-near compositions of these “UV-PE:N” and “UV-PE:O” films were determined by X-ray photoelectron (XPS), and by Fourier transform (reflection–absorption) infrared (FTIR) spectroscopies. The two types of films were compared with plasma polymers deposited using low-pressure radio-frequency (r.f.) glow discharges in similar gas flow mixtures, “PPE:N” and “PPE:O”. VUV-photochemistry appears to be superior to plasma-chemistry in its capability to produce nearly “mono-functional” organic thin films, ones that are rich in primary amines, –NH₂, and in carboxylic acid groups, –COOH, respectively.     

Molecular Logic Gates and Switches Based on 1,3,4‐Oxadiazoles Triggered by Metal Ions

Organic molecular devices for information processing applications are highly useful building blocks for constructing molecular‐level machines. The development of “intelligent” molecules capable of performing logic operations would enable molecular‐level devices and machines to be created. We designed a series of 2,5‐diaryl‐1,3,4‐oxadiazoles bearing a 2‐(para‐substituted)phenyl and a 5‐(o‐pyridyl) group (substituent X=NMe₂, OEt, Me, H, and Cl; 1 a – e ) that form a bidentate chelating environment for metal ions. These compounds showed fluorescence response profiles varying in both emission intensity and wavelength toward the tested metal ions Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺ and the responses were dependent on the substituent X, with those of 1 d being the most substantial. The 1,3,4‐oxadiazole O or N atom and pyridine N atom were identified as metal‐chelating sites. The fluorescence responses of 1 d upon metal chelation were employed for developing truth tables for OR, NOR, INHIBIT, and EnNOR logic gates as well as “ON‐OFF‐ON” and “OFF‐ON‐OFF” fluorescent switches in a single 1,3,4‐oxadiazole molecular system.     

Push–Pull archetype of reduced graphene oxide functionalized with polyfluorene for nonvolatile rewritable memory

A solution‐processable PFTPA‐convalently grafted reduced graphene oxide (RGO‐PFTPA) was synthesized by the 1,3‐dipolar cycloaddition of azomethine ylide. Bistable electrical switching and nonvolatile rewritable memory effects were demonstrated in a sandwich structure of indium tin oxide/RGO‐PFTPA/Al. The switch‐on voltage of the as‐fabricated device was around ?1.4 V, and the ON/OFF‐state current ratio was more than 10³. The ON–OFF transition process is reversible because the application of a high enough positive voltage can induce the reverse transfer of electrons, reducing the conductivity back to its initial OFF state. Both the OFF and ON states are accessible and very stable under a constant voltage stress of ?1 V for up to 3 h, or under a pulse voltage stress of ?1 V for up to 10⁸ continuous read cycles (pulse period = 2 μs, pulse width = 1 μs). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization of acrylonitrile in miniemulsion

Photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization of acrylonitrile (AN) in miniemulsion was reported. PET-RAFT polymerization of acrylonitrile (AN) was successfully accomplished with 4-cyanopentanoic acid dithiobenzoate (CPADB) as chain transfer agent (CTA), sodium dodecyl sulfate (SDS) as emulsifier, hexadecane (HD) as co-stabilizer and TiO₂ as photocatalyst at 25?°C. The linear first-order kinetic plots were observed in miniemulsion with different amounts of SDS. Excellent temporal control was demonstrated by switching between ON/OFF states multiple times, and the prepared PAN macro-CTA was used successfully to perform the chain extension experiments, indicating high retention of chain end functionality. Furthermore, the obtained PAN was amidoximated with NH₂OH·HCl. The Cd²⁺ was extracted with amidoxime (–C(NH₂)=NOH) from aqueous solutions. The maximum adsorption of 98.6% Cd²⁺ with 400?mg of the adsorbent was observed at pH 6.0 and an initial Cd²⁺concentration of 4?mmol/L.     

Temperature-Responsive Electrocatalysis Based on Poly(N-Isopropylacrylamide)-Modified Graphene Oxide (PNIPAm-GO)

Poly(N-isopropylacrylamide)-modified graphene oxide (PNIPAm-GO), which is a type of thermally responsive GO, was designed and synthesized through a covalent “grafting-from” strategy. The as-prepared modified nanosheets integrated the individual advantages of two components, such as the thermal sensitivity of the PNIPAm terminal as well as the conductivity and the open 2D structure of the GO substrate. PNIPAm-GO was able to perform the reversible regulation of hydrophilicity/hydrophobicity in aqueous solution upon variations in the temperature. Such a unique property might also lead to the utilization of PNIPAm-GO as an intelligent electrode material to achieve a switchable electrochemical response toward a [Fe(CN)₆]^3−/4− probe. The PNIPAm-GO modified glassy carbon electrode (PNIPAm-GO/GC electrode) was able to exhibit better electrochemical performance in an ON/OFF switching effect than the PNIPAm-modified glassy carbon electrode (PNIPAm/GC electrode) without GO owing to the intrinsic properties and large surface area of the introduced GO. Moreover, it was found that the PNIPAm-GO/GC electrode also displayed excellent thermally responsive electrocatalysis toward the detection of 1,4-dihydro-β-nicotinamide adenine dinucleotide (NADH) and dopamine (DA), which resulted in two different catalytic statuses on the same electrode. This kind of switchable catalytic performance of the PNIPAm-GO/GC electrode might greatly enhance the flexibility of its application, and thus it is expected to have wide potential for applications in the fields of biosensors and biocatalysis.     

A Brønsted‐Ligand‐Based Iron Complex as a Molecular Switch with Five Accessible States

A mononuclear Fe^II complex, prepared with a Brønsted diacid ligand, H₂L (H₂L=2‐[5‐phenyl‐1H‐pyrazole‐3‐yl] 6‐benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states. The spin crossover (SCO) complex, [Fe^II(H₂L)₂](BF₄)₂ ( 1_A ), exhibits abrupt spin transition at T_1/2=258 K, and treatment with base yields a deprotonated analogue [Fe^II(HL)₂] ( 1_B ), which shows gradual SCO above 350 K. A range of Fe^III analogues were also characterized. [Fe^III(HL)(H₂L)](BF₄)Cl ( 1_C ) has an S=5/2 spin state, while the deprotonated complexes [Fe^III(L)(HL)], ( 1_D ), and (TEA)[Fe^III(L)₂], ( 1_E ) exist in the low‐spin S=1/2 state. The electronic properties of the five complexes were fully characterized and we demonstrate in situ switching between multiple states in both solution and the solid‐state. The versatility of this simple mononuclear system illustrates how proton donor/acceptor ligands can vastly increase the range of accessible states in switchable molecular devices.     

A Metalloregulated Four‐State Nanoswitch Controls Two‐Step Sequential Catalysis in an Eleven‐Component System

The nanomechanical switch 1 with its three orthogonal binding motifs—the zinc(II) porphyrin, azaterpyridine, and shielded phenanthroline binding station—is quantitatively and reversibly toggled back and forth between four different switching states by means of addition and removal of appropriate metal‐ion inputs. Two of the four switching stages are able to initiate catalytic transformations (ON1, ON2), while the two others shut down any reaction (OFF1, OFF2). Thus, in a cyclic four‐state switching process the sequential transformation A + B + C → AB + C → ABC can be controlled, which proceeds stepwise along the switching states OFF1→ON1 (click reaction: A + B → AB )→OFF2→ON2 (Michael addition: AB + C → ABC )→OFF1. Two consecutive cycles of the sequential catalysis were realized without loss in activity in a reaction system with eleven different components.