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David A. Leigh et al. Angew. Chem. Int. Ed. 2005 , 44 , 3062-3067

Patterning through Controlled Submolecular Motion: Rotaxane-Based Switches and Logic Gates that Function in Solution and Polymer Films. David A. Leigh et al. Angew. Chem. Int. Ed. 2005 , 44 , 3062-3067. Tobe Lab. Keiji Nishihara. Contents. ・ Introduction. Rotaxane Structure.

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David A. Leigh et al. Angew. Chem. Int. Ed. 2005 , 44 , 3062-3067

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  1. Patterning through Controlled Submolecular Motion: Rotaxane-Based Switches and Logic Gates that Function in Solution and Polymer Films David A. Leigh et al. Angew. Chem. Int. Ed.2005, 44, 3062-3067 Tobe Lab. Keiji Nishihara

  2. Contents ・Introduction Rotaxane Structure Molecular Switches Materials Applications ・Results and Discussions ・Summary

  3. Rotaxane Structure Macrocycle ・Macrocycle and thread are mechanically interlocked but are not covalently bonded. High mobility Thread Stopper ex. Shuttling, Circumrotation ・Synthesis of rotaxane was very difficult for its peculiar structure. ・By using host-guest interaction or self-assembly, synthesis of rotaxane becomes more easily and efficiently since the late 1980s.

  4. Concept of Molecular Switches External stimuli : light, redox, protonation, pH, temperature, solvent effect “Off state” ・A rotaxane in which the positon of macrocycle can be controlled by changing the stability of station with external stimuli. Shuttling “On state” Molecular Switches Response : conductivity, circular dichroism, fluorescence Station: the site where the macrocyle exists stable

  5. Materials Applications ground-state: Green after a +1 V oxidizing potential: Red/Purple relaxed back to the ground-state: Green The electrochromic response of the solid-state polymer devices. Only simple rotaxanes have been used to create patterned surfaces. J. R. Heath et al., Angew. Chem. Int. Ed. 2004, 43, 6486-6491. ・There are few examples where shuttling has been demonstrated in polymer-based media. D. A. Leigh et al., Science2003, 299, 531. Suitable for materials applications

  6. Design of Thread 1 Glycylglycine: hydrogen-bonding site, “station” Second stopper C11 alkyl chain: “solvophobic” station Anthracene: fluorophore (also act as “stopper”)

  7. Design of Rotaxane 2, 3, and 3・2H+・2CF3CO2- ・Quenching the fluorescence of anthracene though distance-dependent electron transfer

  8. Partial 1H NMR spectra in CDCl3 (400 MHz, 298 K) thread 1 rotaxane 2 ・The signals for Hc and He of glycylglycine station are shielded by d=1.2 and 0.4 ppm in the rotaxane. The macrocycle resides principally over the peptide residue of the rotaxane.

  9. X-ray crystal structure of 3’ (3’: a close structural analogue of rotaxane 3.) ・the macrocycle binding to the glycylglycine station though a network of intercomponent hydrogen bonds.

  10. Partial 1H NMR spectra in [D6]DMSO (400 MHz, 298 K) alkyl chain thread 1 rotaxane 2 ・the signals of the alkyl chain: strongly shielded ・the signals of the glycylglycine unit: essentially unchanged The macrocycle encapsulates the alkyl chain.

  11. Functional group interaction in solution CHCl3 molecule: solvation ・Solvent effect In CHCl3 (chloroform) : nonpolar solvent amide-amide hydogen bonding : morefavorable the macrocycle held firmly on the peptide station DMSO molecule: solvation In DMSO (dimethylsulfoxide) : aprotic polar solvent alkyl chain-phenyl ring solvophobic interaction: favorable the macrocycle to be localized on alkyl-chain station

  12. Fluorescence of rotaxane 2 in DMSO ・The ratio of fluorescence quantum yields is as high as 15: 1 in CH2Cl2 The switching mechanism in solution: (lex=340 nm, 1 x 10-5 M, 298 K) ・The variations in intensity observed with the different solvents is caused by the change in the relative separation of the fluorophore and quencher.

  13. Polymer analogues of 2 and 3 ・[2]rotaxane P5 and P6 contained approximately 10% w/w of peptide rotaxane endgroups. Poly(methyl methacrylate) (PMMA)-based: nonpolar ・1H NMR studies in CDCl3 and [D6]DMSO The behavior of polymers P5 and P6 in solution exactly mirrored those of the small-molecule analogues, 2 and 3. ・The polymer films were of good optical quality!

  14. Effect of exposing to DMSO vapor: shuttling before ・No fluorescence of the P5 film when illuminated with UV light In the nonpolar environment of PMMA-like film the macrocycle resides over the peptide portion of the thread Efficient quenching of the anthracene fluorescence Exposing the P5-coated slides to DMSO vapor: shuttling the characteristic blue anthracene fluorescene after Masked with aluminium grids ・The system is reversible.

  15. Effect of exposing to CF3CO2H vapor: protonation before ・P6 films were fluorescent when illuminated with UV light. The pyridine units of the macrocycle need to be protonated to quench the excited state of anthracene. Exposing P6-coated slides to CF3CO2H vapors (P6→P6・(2H+・2CF3CO2-)n: protonation) Fluorescence was no longer observed. after A distinct pattern of dark (nonfluorescent) bands resulting from P6 films upon exposure to CF3CO2H vapor through a striped aluminum mask (a).

  16. The response of P6 to the different combination of two stimuli 1. rotation of the aluminum grid by 90º 2. exposure of the film shown in (b) to DMSO vapor ・The response of P6 to the different combinations of two stimuli (DMSO and protons) corresponds to an “INHIBIT” logic gate. Criss-cross pattern was obtained. ・The effect of the acid stimulus involves some deterioration in the optical quality of the film.

  17. Molecular logic gates: “INHIBIT” logic gate For a recent review: A. P. de Silva, N. D. McClenaghan, Chem.Eur. J. 2004, 10, 574-586 INHIBITOR: Input2 ・A NOT circuit preceding one terminal of an AND gate acts as an INHIBITOR. Output = Input1・Input2 ・In the case of rotaxane P6, exposing to DMSO vapor acts as INHIBITOR. MOLECULAR-SCALE LOGIC GATES

  18. Summary ・The authors have described a class of molecular shuttles in which translational isomerism of the components can be controlled to either permit or preclude fluorescence quenching by intercomponent electron transfer in both solution and polymer films. ・The optical response can be unambiguously ascribed to changes in the relative positions of macrocycle and thread. ・The present work demonstrates that some of the switching mechanisms, properties, and logic operations established for molecular shuttles in solution can be transferred to media that are more suitable for materials which function through controlled submolecular motion.

  19. Molecular Switches 1: conductivity External stimuli: Redox ・at a specific voltage, this rotaxane switches from a stable Off state to metastable On state with a different conductivity. A molecular switch tunnel junction in its Off and On states. (left) Structural formula of a bistable [2]rotaxane A. H. Flood et al., Science2004, 306, 2055-2056.

  20. Molecular Switches 2: circular dichroism External stimuli: light (E)-isomer glycyl-L-leucine (Gly-Leu) unit: well-exprssed chiral environment ・Upon photoisomerism of the olefin station (E→Z), the macrocycle moves to the glycyl-L-leucine (Gly-Leu) unit. (Z)-isomer Only (Z)-isomer gives a CD response. D. A. Leigh et al., J. Am.Chem. Soc. 2003, 125, 13360-13361.

  21. Molecular Switches 3: fluorescence anthracene unit External stumuli: light (E)-isomer ・(E)-isomer converted into (Z)-isomer by photoisomerism. (Z) (E) PSS (Z)-isomer A remarkable 200:1 intensity ratio between (E)-and (Z)-isomer. electron transfer pyridinium unit Because of distance-dependent electron transfer from anthracene unit to pyridinium units. D. A. Leigh et al., J. Am. Chem. Soc. 2004, 126, 12210-12211.

  22. Functional group interaction profiles (FGIP) C. A. Hunter Angew. Chem. Int. Ed. 2004, 43, 5310-5324 In chloroform: nonpolar In DMSO: polar contour lines (等高線) Blue : DDGH-bond < 0 favorable interaction Red : DDGH-bond > 0 unfavorable interaction ・FGIP provide a benchmark for estimating the magnitudes of intermolecular interactions. a: hydrogen-bond donor constant b: hydrogen-bond acceptor constant

  23. Functional group interaction profiles (FGIP) in chloroform amide-amide interaction: favorable ・The authors expect the tertiary structure to feature the macrocycle held firmly on the peptide station by well-defined hydrogen-bonding network. alkyl chain-phenyl ring interaction: unfavorable Strong quenching of the anthracene fluorescence

  24. Functional group interaction profiles (FGIP) in DMSO amide-amide interaction: unfavorable ・The authors expect the macrocycle to be localized on alkyl-chain station but in a variety of positions owing to the general solvophobic interactions. alkyl chain-phenyl ring interaction: favorable

  25. Electron-transfer process in solution The very efficient quenching observed in nonpolar solvents (ex. chloroform, dichloromethane) The electron-transfer process in rotaxanes 2 and 3・2H+ is close to the Marcus optimal region. ・The electron transfer process in the rotaxanes: barrierless and insensitive to the polarity of the solvent. The switching mechanism in solution: ・The variations in intensity observed with the different solvents is caused by the change in the relative separation of the fluorophore and quencher.

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