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Review
. 2015 Sep 23;115(18):10081-206.
doi: 10.1021/acs.chemrev.5b00146. Epub 2015 Sep 8.

Artificial Molecular Machines

Sundus Erbas-Cakmak  1 , David A Leigh  1 , Charlie T McTernan  1 , Alina L Nussbaumer  1
Affiliations
Review

Artificial Molecular Machines

Sundus Erbas-Cakmak et al. Chem Rev. .
No abstract available

PubMed Disclaimer

Figures

Figure 1
Figure 1
Maxwell’s demons. (a) A “temperature demon” sorts particles according to velocity, generating a temperature gradient. (b) A “pressure demon” sorts particles according to their direction of movement, generating a pressure gradient.
Figure 2
Figure 2
(a) In Smoluchowski’s Trapdoor, a spring-loaded gate separates the two sections of a container. The lack of energy dissipation leads to a longer duration of opening and thus a uniform particle distribution between the sections. (b) Feynman’s ratchet-and-pawl device. The asymmetry of the teeth of the ratchet cog was intended to drive directional movement. However, when T1 = T2, the rotation is nondirectional.
Figure 3
Figure 3
An on–off ratchet: (a) the particles are located in an energy minima, (b) the potential is turned off so that diffusion can occur for a short time, and (c) the potential is turned on again. As the potential is asymmetric, particles have a greater probability of being trapped in an adjacent well to the right of the original one than to the left. (d) Relaxation into the local energy minima leads to the average position of the particles moving to the right.
Figure 4
Figure 4
A flashing ratchet. In (a) and (c), the particle starts in a green or orange well, respectively. Raising this energy minima while lowering the adjacent maxima and minima triggers movement by Brownian motion (b) to (c) or (d) to (e). By continuously varying the relative heights of the energy barriers and minima of the energy wells, the particle can be directionally transported.
Figure 5
Figure 5
A temperature or diffusion ratchet. (a) The particles are located in an energy minima on the potential-energy surface, with energy barriers ≫kBT1. (b) The temperature is increased so that the height of the barriers is ≪kBT2, and free diffusion is allowed to occur for a short time. (c) As the temperature is lowered again, the asymmetric potential energy surface means that the particles have a greater probability of being trapped to the right of their initial position. (d) Relaxation to the local energy minima.
Figure 6
Figure 6
A rocking ratchet. (a) Particles are located in an energy minima on the potential energy surface. (b) A directional force is applied to the left. (c) An equal and opposite directional force is applied to the right. (d) Removal of the force and relaxation to an energy minima leads to the average position of the particles moving to the right.
Figure 7
Figure 7
An information ratchet. In (a) and (d) the dotted lines represent the transfer of information about the position of the particle. (b) The position of the particle lowers the energy barrier to movement to the right-hand well but not the left. (c) The particle moves by Brownian motion.
Figure 8
Figure 8
Chemical structure of a triaryl molecule as an example of a molecular propeller.,
Figure 9
Figure 9
(a) Molecular bevel gear 2, consisting of two 9-triptycyl groups joined through a bridge head carbon to a central atom. (b) X-ray structure of the molecular bevel gear (side view). (c) X-ray structure of the molecular bevel gear (top view). Adapted with permission from ref (156). Copyright 1984 American Chemical Society.
Figure 10
Figure 10
(a) Chemical structure of tris-monodentate disk shaped ligand 3 and hexakis-monodentate ligand 4. (b) Schematic representation of complex [Ag3(3)2] shown as its M-helical enantiomer. (c) X-ray structure of complex [Ag3(3)2]. (d) Schematic representation of the flipping motion of the rings attached to the disks and subsequent ligand exchange from 1-A, 3-E, and 5-C in M to 1-B, 3-F, and 5-D in P. The direction of rotation in the M to P transition is opposite to that of a subsequent P to M′ transition. Reprinted with permission from refs (197) and (200). Copyright 2003 and 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 11
Figure 11
(a) Schematic illustration of a crank mechanism that translates linear motion into rotary motion in cylinder engines. (b) Schematic representation of a molecular crank mechanism. (c) Chemical structure of a synthetic molecular crank 5. Reprinted with permission from ref (201). Copyright 2010 Royal Society of Chemistry.
Scheme 1
Scheme 1. Molecular Brakes Operated by (a) Hg2+ Binding and (b) Sulfur Oxidation; and (c) Proposed Transition State Stabilization in Shimizu’s System,,
Scheme 2
Scheme 2. A Molecular Switch Flipped by Singlet Oxygen
Figure 12
Figure 12
(a) Kelly’s ratchet-and-pawl 10. (b) Enthalpy change on rotation of helicene. Reprinted with permission from ref (212). Copyright 1997 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Scheme 3
Scheme 3. Chemically Driven Directional 120° Rotation of Kelly’s Triptycene Rotor 11(216)
Scheme 4
Scheme 4. Directional 360° Rotation about a Single Bond via Four States A–D
Rotation is restricted in A and C by covalent bonds, although helical inversion is allowed, and in B and D by nonbonded interactions, with directional control of rotation being provided by stereospecific covalent bond cleavage.
Figure 13
Figure 13
(a) X-ray crystal structure of porphyrin double decker complex 16 with cerium(IV). Reprinted with permission from ref (228). Copyright 1989 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (b) Representation of the cooperative binding of guest molecules to porphyrin double decker complex 17.
Figure 14
Figure 14
Cerium(IV) bis(porphyrinate) double decker (top unit) and a rhodium(III) porphyrin-based side cog. The two units are connected through a coordination bond between rhodium(III) and a pyridyl group.
Scheme 5
Scheme 5. Control of Rotation in Ferrocene Complex 19 through Protonation
Figure 15
Figure 15
(a) Dicarbollide ligand 202–. (b) Metallocarborane [Ni(20)2], an electrochemically controlled rotary switch.
Scheme 6
Scheme 6. (a) Negative Allosteric Receptor 21, Where Binding of Tungsten Forces Ring Contraction and Steric Clash of the 3- and 3′-Substituents of the Bipyridyl Unit; and (b) Positive Allosteric Receptor 22(263,264)
Figure 16
Figure 16
(a) Molecular tweezer 23, arrows indicate direction of contraction. (b) Clip 25, where the aa form is favored in the presence of a guest. (c) Clip 26, where ion binding enhances guest affinity. (d) Crystal structure of uncomplexed and complexed 24.,,, X-ray crystal structure reprinted with permission from ref (282). Copyright 2007 American Chemical Society.
Scheme 7
Scheme 7. (a) Prevention of Organic Guest Binding on Complexation of Copper to 27; and (b) Organic Guest Is Only Bound in the Zinc-Complexed Form of 28(288)
Scheme 8
Scheme 8. Chelation Control of Equatorial/Axial Conformers and Haberhauer’s Molecular Hinge,,
Reprinted with permission from ref (299). Copyright 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Scheme 9
Scheme 9. Resorcin[4]arene 31, Vase and Kite Conformers, Stoddart’s Self-Complexing Lock 32, and Feringa’s Self-Complexing Rotor 33(98,321,322,327),
Reprinted with permission from refs (321) and (327). Copyright 1997 and 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Scheme 10
Scheme 10. Hamilton’s Acid Sensitive Switch
Scheme 11
Scheme 11. pH-Driven Conformational Change in Oligomeric System 35(330)
Scheme 12
Scheme 12. Large-Scale Extension of a Ligand Strand upon Pb(II) Complexation,
Scheme 13
Scheme 13. (a) Molecular Scissors 38; and (b) Structure of Molecular Hinge 39(414)
Irradiation at 350 nm initiates photoisomerization from the trans to cis isomer of the azobenzene moiety (closed to open molecular scissor); irradiation at >400 nm induces the reverse.
Figure 17
Figure 17
(a) Chemical structure of a molecular brake 40 with a 2,5-dimethylbenzene unit as the rotor. (b) X-ray crystal structure. (c) Schematic representation of this photoinduced molecular brake. X-ray crystal structure reprinted with permission from ref (418). Copyright 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Scheme 14
Scheme 14. Minimization of Steric Interactions between Aromatic Groups and Substituent Results in (P,P)-(trans)-41-Stable Ground-State Conformation, with Axial Substituents
(i) Photochemical isomerization leaves substituents in the unstable equatorial conformation (M,M)-(cis)-41-unstable. (ii) Steric strain is released by a thermally activated helicity inversion leading to (P,P)-(cis)-41-stable. (iii) Photoisomerization from cis to trans. (iv) Helical inversion completes a full rotation.
Figure 18
Figure 18
Comparison of the general structures for the first (41) and second (42) generations of Feringa’s molecular motors.
Figure 19
Figure 19
Structure of molecular brake 43.
Scheme 15
Scheme 15. Hydrazone-Based Switches
(a) Protonation of the pyridyl nitrogen of compound (E)-44 induces E → Z isomerization. (b) The quinoline unit in (E)-45 provides a binding site for a Zn2+ ion, which is now the trigger for E → Z isomerization.
Scheme 16
Scheme 16. Switching Cascade of Hydrazone Rotary Switches
Scheme 17
Scheme 17. Light-Operated Molecular Tweezers
Scheme 18
Scheme 18. Decreased Drug Binding Affinity by a pH-Induced Conformational Change
Figure 20
Figure 20
Orthogonal exclusion of an azobenzene and a viologen encapsulated by CB[8].
Figure 21
Figure 21
Na+-induced twisting in helicate 52. Reprinted with permission from ref (589). Copyright 2010 Nature Publishing Group.
Figure 22
Figure 22
Control of anion concentration in solution by a photoresponsive foldamer. Reprinted with permission from ref (595). Copyright 2010 American Chemical Society.
Scheme 19
Scheme 19. Excited-State Intramolecular Proton Transfer in HBT,
Scheme 20
Scheme 20. Intramolecular Anion Translocation Mediated by (a) Redox and (b) Ligand Exchange
Scheme 21
Scheme 21. Redox-Mediated Intramolecular Ion Translocation
Scheme 22
Scheme 22. Redox-Mediated Pd Translocation in an Aromatic Sandwich Complex
Scheme 23
Scheme 23. (a) The First “Molecular Shuttle”, 61; and (b) Degenerate Peptide-Based Molecular Shuttles 62–64 of Varying Linker Length
Figure 23
Figure 23
Idealized model of binding in degenerate molecular shuttles. Barrier height is dependent on the energy required to break interactions between macrocycle and station and a distance-dependent diffusional component.
Scheme 24
Scheme 24. Complexation of Copper Leads to the Introduction of a Large Kinetic Barrier to Shuttling
Figure 24
Figure 24
Idealized potential energy surface for macrocycle shuttling in a degenerate, two-station molecular shuttle.
Scheme 25
Scheme 25. Light-Driven Directional CD Shuttling in a [2]Rotaxane
Scheme 26
Scheme 26. Solvent-Dependent Shuttling and Induced CD Response in a [2]Rotaxane
Figure 25
Figure 25
Potential energy diagram of a rotaxane-based bistable molecular shuttle.
Scheme 27
Scheme 27. A pH-Driven Molecular Shuttle
Scheme 28
Scheme 28. A Redox-Driven Molecular Shuttle,
Scheme 29
Scheme 29. Chloride-Induced Molecular Shuttling in a [2]Rotaxane
Scheme 30
Scheme 30. Hydrolytic or Entropically Driven Restriction of Shuttling in a [2]Rotaxane
Scheme 31
Scheme 31. Chemically Driven Shuttling in a [2]Rotaxane
Figure 26
Figure 26
Photoinitiated redox-driven shuttling in a [2]-rotaxane initiated by (i) irradiation and (ii) subsequent reduction of viologen station. (iii) Competing back electron transfer from one-electron reduced viologen to Ru3+. (iv, v) With continuous irradiation the macrocycle shuttles to the dimethylviologen station. (vi) Ceasing illumination restores the macrocycle to its original position.
Figure 27
Figure 27
[2]Rotaxane 74 acts as an irreversible mechanical switch. The silyl ether is too bulky to allow macrocycle shuttling between the two succinamide stations.
Figure 28
Figure 28
Operation of a compartmentalized molecular machine, which corresponds to a two-state Brownian flip-flop. Operation steps: (a) Desilylation (80% aqueous acetic acid); (b) E → Z photoisomerization (hν at 312 nm); (c) resilylation (TBDMSCl); and (d) Z → E thermal isomerization (catalytic piperidine).
Figure 29
Figure 29
Initially the system is balanced (in proportion to the sizes of the two compartments), with an equal density of particles in the left and the right compartments. By changing the volume of the left-hand compartment, the system becomes statistically unbalanced. Opening the door allows the particle to redistribute according to the new size of the compartments. Closing the door ratchets the new distribution of the particles. Restoring the left compartment to its original size results in a concentration gradient of the Brownian particles across the two compartments. Here, the size of the compartment represents the energy level of the macrocycle-station system.
Scheme 32
Scheme 32. Structure and Mechanism of the Information Ratchet
(a) Gate closed, but energy transfer from the macrocycle is efficient. (b and c) Gate is open, allowing free shuttling of the macrocycle. (d) The macrocycle is on the green station, intramolecular energy transfer (ET) from the macrocycle is inefficient; intermolecular energy transfer from PhCOCOPh dominates (closing the gate).
Scheme 33
Scheme 33. Chemically Driven Molecular Information Ratchet
Scheme 34
Scheme 34. Directional Transport of a Macrocycle in a [2]Rotaxane Three-Compartment Chemical Information Ratchet
Figure 30
Figure 30
Photodriven directional translational motion in pseudorotaxanes 86–87. Reprinted with permission from ref (811). Copyright 2013 American Chemical Society.
Figure 31
Figure 31
Effect of water on the rate of pirouetting of a macrocycle about an axle. Reprinted with permission from ref (698). Copyright 2013 Nature Publishing Group.
Figure 32
Figure 32
Directional circumrotation in a [3]catenane. (i) hν (350 nm), (ii) hν (254 nm), (iii) heating; or heating with catalytic ethylenediamine; or catalytic Br2, hν (400–670 nm). Adapted with permission from ref (883). Copyright 2003 Nature Publishing Group.
Scheme 35
Scheme 35. Directional Circumrotation in [2]Catenane 91(885)
Figure 33
Figure 33
Schematic representation of an electric revolving door. (a) Door closed-switch on leading to high conductance. (b) Door open-switch off leading to low conductance.
Scheme 36
Scheme 36. A Molecular Rectifier
(a) High conductance predicted. (b) Low conductance predicted.
Figure 34
Figure 34
One enantiomer of chiral molecule 94, in which directional rotational motion was driven by linearly polarized laser pulses and studied by quantum and classical mechanical simulations.
Figure 35
Figure 35
Nonpolar 95 and dipolar 96 altitudinal rotors mounted on an Au(111) surface. Note that rotor and flanking aryl rings are arbitrarily shown perpendicular to the surface for clarity.
Figure 36
Figure 36
(a) Molecular structure of transition-metal-based gyroscopes 97 and 98. (b) X-ray structure of compound 97. X-ray crystal structure reprinted with permission from ref (983). Copyright 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 37
Figure 37
(a,b) Proposed designs for swimmers viable at the nanoscale. (c,d) Potential molecular solutions.
Figure 38
Figure 38
(a) Chemical structure and (b–f) STM micrographs of translational motion of a four-wheeled “nanocar” on an Au(111) surface at 200 °C. Wheels are shown by yellow spots, and the path is highlighted with a white arrow. Reprinted with permission from ref (1129). Copyright 2005 American Chemical Society.
Figure 39
Figure 39
(a) Structure of a cerium-centered double-decker molecule. (b) STM micrographs of the molecules assembled on Au(111) surface. The two distinct isomers, due rotational chirality, are shown in white and blue crosses. (c) Space-filling model of the two chiral species. Reprinted with permission from ref (1134). Copyright 2011 American Chemical Society.
Figure 40
Figure 40
(a) Chemical structure of a rotary motor with the groups responsible for double-bond isomerization (red) and helix inversion (blue) highlighted. (b) Schematic representation of a full 360° rotation with sequential double-bond isomerization and helix inversion (hexyl substituents are omitted for clarity). (c) Schematic representation of electron tunneling exciting the molecule and inducing translational motion on the surface. (d) Cartoon representation of the motion. Reprinted with permission from ref (1135). Copyright 2011 Nature Publishing Group.
Figure 41
Figure 41
(a) Chemical structure of a rotaxane with fumaramide and succinamide stations depicted in green and orange, respectively. (b) Schematic representation of macrocycle movement on a thread attached to a gold surface as a result of the force exerted by an AFM probe. Application of force by cantilever movement (I,II) was followed by repositioning of the macrocycle (III) or detachment of the PEO tether (IV) depending on the strength of the force. Reprinted with permission from ref (1143). Copyright 2011 Nature Publishing Group.
Figure 42
Figure 42
Communication between molecular devices. Acid generated upon conversion of merocyanine (MEH+) to spiropyran (SP) protonates a pyridine, and leads to subsequent complexation of the pyridinium ion (103+) by a calix[6]arene (104).
Scheme 37
Scheme 37. Expansion and Contraction Allosterically Controlled by Ligand Coordination
The Zn(II) center acts as a catalytic unit, and diethylaminomethylanthracene is used as the reporter.
Figure 43
Figure 43
(a) Chemical structure of the t-butylphenyl and BODIPY-substituted foldamers, and (b) X-ray structure of the t-butylphenyl functionalized foldamer. Carbon atoms of the t-butyl groups and all hydrogen atoms except OH and NH have been omitted for clarity. (c) Schematic representation of conformational switching. D and A represent energy donor and acceptor modules, respectively.− Parts (a) and (c) are adapted with permission from ref (1268). Copyright 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Part (b) is reprinted with permission from ref (1269). Copyright 2006 American Chemical Society.
Figure 44
Figure 44
(a) Ligand-induced variation of the chemical shifts (11B (160 MHz) and 1H NMR (500 MHz)) of the helix in CD3OD at 298 K. (b) Schematic representation of fast exchange between two degenerate helical conformers with a single NMR signal and (c) induced bias of helicity upon ligand binding (yellow), and the anisochronous NMR signal generated. Adapted with permission from ref (1298). Copyright 2013 Nature Publishing Group.
Scheme 38
Scheme 38. Photoisomerization-Dependent Shuttling of an α-Cyclodextrin on an Azobenzene and Stilbene Bearing Thread with Two Naphthalimide Derivatives as Fluorescent Stoppers
The percentage of the major isomer in the photostationary state is shown over the reaction arrows. The truth table for a half-adder logic gate is shown, with the inputs being 380 nm (I1) and 313 nm (I2) irradiation, and outputs being the change in absorbance (O2) and fluorescence (O1) values.
Figure 45
Figure 45
(a) Chloride-dependent shuttling of tetralactam macrocycle, and (b) subsequent fluorescence enhancement in CHCl3 upon titration with tetrabutylammonium chloride. (c) Rotaxane solution in the absence (left) or presence (right) of chloride. Adapted with permission from ref (1310). Copyright 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 46
Figure 46
(a) Chemical structures of 115, and the open and closed forms of 114. (b) Schematic representation of light modulated switch and K+/18-crown-6-mediated complexation. (c) Fluorescence quenching of the Eu3+ complex upon UV irradiation in 1:1 CH3CN/CHCl3. Fluorescence before (I) and after (II) excitation at 390 nm (c inset). Reprinted with permission from ref (1314). Copyright 2013 American Chemical Society.
Figure 47
Figure 47
(a) Chiraloptical switching upon photoinduced shuttling of the macrocycle between fumaramide (green) and peptide (orange) stations; the chiral center of the peptide station is highlighted by a black circle. (b) Percentage of E isomer calculated using 1H NMR (left y axis) and induced CD absorption at 246 nm after alternating irradiation between 254 nm (half integer) and 312 nm (integers) (right y axis). Reprinted with permission from ref (1326). Copyright 2003 American Chemical Society.
Figure 48
Figure 48
(a) Solvent-induced shuttling on a tetracyanobutadiene bearing rotaxane 117. (b) Proposed assembly of rotaxane and SEM images in CHCl3/n-C6H14 (1/1, v/v), (c) in CHCl3/MeOH (1/1, v/v), and (d) in DMSO. Reprinted with permission from ref (1327). Copyright 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Scheme 39
Scheme 39. β-Galactosidase-Triggered Release of Triglycyl Peptide 120 from the [2]Rotaxane Propeptide 118 and 119(1351)
Figure 49
Figure 49
(a) The structure and operation of walker 125, which uses dynamic imine exchange chemistry. Amine footholds are highlighted in blue and red. Each molecule is labeled with one or two numbers in parentheses indicating the amine footholds to which the walker is attached (foothold amines are assigned with numbers starting from the left). (b) 1H NMR spectra of indicated protons in CDCl3. H7 corresponds to a side product in which the walker is detached from the track. Reprinted with permission from ref (1395). Copyright 2012 American Chemical Society.
Figure 50
Figure 50
(a) The chemical structure of the model walker 127, and (b) gradual change in 1H NMR of the model walker in d6-DMSO upon formation of new positional isomer on the track. Ratio of (1):(2) isomers reaches 1:0.9 after 15 h of operation. (c) Chemical structure of the walker on a larger track bearing an anthracene moiety, 128. (d) Fluorescence quenching of anthracene after 6.5 h of walking. Reprinted with permission from ref (1397). Copyright 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 51
Figure 51
(a) Chemical structure of walker 129, with each positional isomer labeled in a different color, and amines numbered. (b) Change in the partial 1H NMR spectra over 48 h of operation. (c) Occupancy of each foothold over time. Reprinted with permission from ref (1398). Copyright 2013 American Chemical Society.
Scheme 40
Scheme 40. Structure and Operation of a Small Molecule Walker, Walking along a Molecular Track
Footholds are shown in blue and green; the walker unit is depicted in red. Numbering shows the footholds to which the walker is attached.
Figure 52
Figure 52
Toward directional molecular walkers. (a) Chemical structure and schematic representation of the walker attached to the track, and (b) operation of walking through successive acid–base addition and heating cycles. Reprinted with permission from ref (1403). Copyright 2014 American Chemical Society.
Scheme 41
Scheme 41. Light-Driven Transport of a Molecular Walker along a Molecular Track
Footholds are shown in blue and green; the walker unit is depicted in red. Each molecule is labeled with two numbers in parentheses indicating the two footholds to which the walker is attached. (a) (i) hν (365 nm), CD2Cl2, (ii) DBU, DTT, CHCl3; (b) (i) I2, hν (500 nm), CD2Cl2, (ii) TFA, CHCl3.
Figure 53
Figure 53
(a) Molecular structure of the photoswitchable piperidine base 133, and (b) X-ray structure of the photoswitchable piperidine base 133. X-ray crystal structure reprinted with permission from ref (1418). Copyright 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Scheme 42
Scheme 42. Ring-Opened and Ring-Closed Isomers of the DAE-Modulated Photoswitchable Organocatalyst 134(1421)
Scheme 43
Scheme 43. (a) Reaction of an Amino Acid with PLP Showing the Aldimine 136 Initially Produced, and the Molecular Structure of the Quinonoid 137 Formed after Removal of the Amino Acid’s α-Hydrogen, Which Leads to Racemization; and (b) Photoresponsive PLP Mimic 138(1423)
Figure 54
Figure 54
Schematic representation and molecular structure of a bifunctional organocatalyst integrated in a directional light-driven molecular motor. A, DMAP; B, thiourea hydrogen-bonding donor group. (a) A and B are remote. (b) A and B are in close proximity with M helicity in the (M,M)-cis-140 isomer, preferentially providing the (S) enantiomer of the reaction product. (c) A and B are in close proximity with P helicity in the (P,P)-cis-140 isomer, generating (R) enriched product. Step 1: irradiation at 312 nm at 20 °C. Step 2: heating at 70 °C. Step 3: irradiation at 312 nm at −60 °C. Step 4: temperature −10 °C.
Scheme 44
Scheme 44. Acid–Base Switching of the Position of the Macrocycle, Which Conceals or Exposes the Catalytic Site on the Rotaxane
Figure 55
Figure 55
(a) Allosteric supramolecular triple-layer complex 142, which regulates the catalytic living polymerization of ε-caprolactone. (b) Molecular structures of the components.
Scheme 45
Scheme 45. Schematic Representation of the Reversible Locking and Unlocking of Switchable Catalyst 143(1439)
Figure 56
Figure 56
Porphyrin-catalyzed epoxidation of a butadiene polymer by 144, utilizing a rotaxane architecture. Reprinted with permission from ref (1456). Copyright 2003 Nature Publishing Group.
Scheme 46
Scheme 46. Cyclodextrin Dimer 145 Polymerization Catalyst,
Reprinted with permission from ref (1460). Copyright 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 57
Figure 57
Leigh’s small molecule peptide synthesizer, 146.
Scheme 47
Scheme 47. Operation of Leigh’s Peptide Synthesizer,
Reprinted with permission from ref (666). Copyright 2013 American Association for the Advancement of Science (AAAS).
Figure 58
Figure 58
(a) Molecular structure of linear conjugated phenylethynylene molecular dirotor 147. Rotation of the phenylene rotor (shown with an arrow) creates rotamers with varying degrees of π-conjugation and so wavelengths of emission. (b) X-ray structure of the dirotor 147. X-ray crystal structure reprinted with permission from ref (1462). Copyright 2013 American Chemical Society.
Figure 59
Figure 59
(a) Structure of [2]rotaxane 148. (b) Schematic representation of the structural design components used to create the metal–organic framework. (c) X-ray structure of the tetra-ester precursor to [2]rotaxane 148. (d) X-ray structure of a single unit of the mechanically interlocked molecule, coordinated to four Cu(II) paddlewheel clusters. X-ray crystal structure reprinted with permission from ref (1475). Copyright 2012 Nature Publishing Group.
Figure 60
Figure 60
(a) Rotaxane 149-based molecular switch tunnel junctions and proposed mechanism for the operation. (i) In the ground state, the tetracationic cyclophane (dark blue) mainly encircles the TTF station (green) and the junction exhibits low conductance. (ii) Application of a positive bias results in one- or two-electron oxidation of the TTF units (green → pink), and increases electrostatic repulsion causing (iii) shuttling of the macrocycle to the DNP station (red). (iv) Returning the bias to near −0 V provides a high conductance state, in which the TTF units have been regenerated, but translocation of the cyclophane has not yet occurred due to a significant activation barrier to movement. Thermally activated decay of this metastable state may occur slowly ((iv) → (i), in a temperature-dependent manner) or can be triggered by the application of a negative voltage (v), which temporarily reduces the cyclophane to its diradical dication form (dark blue → orange), allowing facile recovery of the thermodynamically favored coconformation (vi). (b) Example of one design of a molecular switch. The coloring of the functional units corresponds to that used for the structural diagrams.,, Reprinted with permission from ref (14). Copyright 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 61
Figure 61
Color changes in a liquid-crystal film doped with a light-driven rotor. Reprinted with permission from ref (1528). Copyright 2002 American National Academy of Sciences.
Figure 62
Figure 62
(a) Molecular structure of gyrotops 150 and 151. The bulkier 151 does not exhibit rotation. (b) X-ray structure of 150. (c) Single crystal of 150 irradiated with polarized white light. (d) X-ray structure of 151. (e) Single crystal irradiated with polarized white light. For 150, a continuous change in color was observed, due to thermal expansion. Reprinted with permission from ref (1530). Copyright 2012 American National Academy of Sciences.
Figure 63
Figure 63
(a) Chemical structures of rotaxane initiators 152 and 153 and the corresponding PMMA-based polymers 154, 155, and 155·2H2+. (b) Images obtained by casting films of polymer 154 on quartz slides, then covering the films with aluminum masks and exposing the unmasked area to DMSO vapor for 5 min. The photographs were taken while illuminating the slides with an 8-W UV lamp (254–350 nm). Reprinted with permission from ref (1536). Copyright 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 64
Figure 64
(a) Aluminum grid used in the experiment. (b) Pattern generated when films of 155 were exposed to trifluoroacetic acid vapor for 5 min through the aluminum-grid mask. (c) Mesh pattern obtained by rotation of the aluminum grid by 90° and exposure of the film shown in (b) to DMSO vapor for a further 5 min; only regions exposed to trifluoroacetic acid but not to DMSO were quenched as shown in the magnified view. Inset: Truth table for an INHIBIT logic gate. The photographs were taken while illuminating the slides with an 8-W UV lamp (254–350 nm). Reprinted with permission from ref (1536). Copyright 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 65
Figure 65
(a) Rotor 156. (b) Rotation of micrometer scale glass rod on doped liquid crystal film. Photos taken at 15 s intervals. Reprinted with permission from ref (1637). Copyright 2001 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Scheme 48
Scheme 48. Molecular Motion Generating a Macroscopic Mechanical Response,,,
Reprinted with permission from ref (1647). Copyright 2015 Nature Publishing Group.
Figure 66
Figure 66
(a) Structure of nanopore gate, and (b) controlled release of guest from nanopores. Reprinted with permission from ref (14). Copyright 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Scheme 49
Scheme 49. Electrode Controlled Macrocycle Shuttling, Leading to Control of the Hydrophilicity of the Surface
Figure 67
Figure 67
Feringa’s tripodal wettability switch 160.
Figure 68
Figure 68
Calix[4]arene 161, used to control surface wettability.
Figure 69
Figure 69
Light switchable rotaxane 162, and transport of a microliter drop of CH2I2 across a flat surface (a–d) and up a 12° incline (e–h). Reprinted with permission from ref (1245). Copyright 2005 Nature Publishing Group.
Scheme 50
Scheme 50. (a) Irreversible Photocleavage of 163 Leading to Pore Opening; and (b) Reversible Photoswitching of 164, Leading to Pore Opening
MscL = mechanosensitive channel.
Figure 70
Figure 70
Proton gradient established by spiropyran (165) shuttling upon differential illumination of the two sides of a membrane. Reprinted with permission from ref (1809). Copyright 2014 Nature Publishing Group.
Figure 71
Figure 71
(a) Tweezer A: in the closed form the arms are bound to the linker unit (blue) by Hg2+ ions through T–Hg2+–T bonds. To open the molecular tweezer, Hg2+ is sequestered by the addition of cysteine. (b) Tweezer B: in acid the arms form an i-motif, thus releasing the linker unit, whereas at pH = 7.2, the i-motif is destroyed resulting in the stabilization of the closed structure. (c) Tweezer C: the linker unit can be released by a complementary strand, the antilinker that opens the tweezers. Reprinted with permission from ref (1914). Copyright 2010 American National Academy of Sciences.
Figure 72
Figure 72
DNA machine reported by Liu and co-workers, which could be used to regulate an enzyme cascade reaction. Reprinted with permission from ref (1915). Copyright 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 73
Figure 73
(a) Programmed migration of two Au nanoparticles. (b) STEM images corresponding to the different structures; the bar corresponds to 20 nm. Reprinted with permission from ref (1916). Copyright 2013 Nature Publishing Group.
Figure 74
Figure 74
Schematic representation of a DNA-based walker and track system. Footholds protrude from the track as single-stranded DNA fragments. Anchor and holding strands enable the walker unit to bind to the footholds by hybridization. Areas with functional importance are labeled, and complementary strands are depicted in the same color for clarity.
Figure 75
Figure 75
(a) Structure of the DNA walker with four “feet” (F1–4) and three “hands” (H1–3). (b) Movement of walker across the DNA origami tile driven by sequentially added DNA “fuel” strands labeled FA. (c) Loading of cargo onto DNA walker. Reprinted with permission from ref (1455). Copyright 2010 Nature Publishing Group.
Figure 76
Figure 76
(a) Operation of DNA-based walker. (b) AFM images of walker. Reprinted with permission from ref (1455). Copyright 2010 Nature Publishing Group.
Figure 77
Figure 77
Walker with a choice of path at a junction. (a) Initially cargo resides on position W, and (b) the use of different set of fuels (F) leads to transport of cargo to either position. A displacing strand (Dz) was used for the fragmentation of the molecular ensemble and subsequent analysis of the cargo position. Reprinted with permission from ref (1843). Copyright 2011 American Chemical Society.
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References

    1. Brown R. A Brief Account of Microscopical Observations Made on the Particles Contained in the Pollen of Plants. Philos. Mag. 1828, 4, 171–17310.1080/14786442808674769. - DOI
    1. Brown R. On the Particles Contained in the Pollen of Plants; and on the General Existence of Active Molecules in Organic and Inorganic Bodies. Edinb. New Philos. J. 1828, 5, 358–371.
    1. Perrin J. In Atoms (English Translation), 2nd ed.; Hammick D. L., Ed.; Constable and Co.: London, 1923.
    1. Einstein A. Über die von der Molekularkinetischen Theorie der Wärme Geforderte Bewegung von in Ruhenden Flüssigkeiten Suspendierten Teilchen. Ann. Phys. 1905, 17, 549–56010.1002/andp.19053220806. - DOI
    1. Feynman R. P.; Leighton R. B.; Sands M.. The Feynman Lectures on Physics; Addison-Wesley: Reading, MA, 1963; Vol. 1, Chapter 46.

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