Mechanical twisting of a guest by a photoresponsive host

Muraoka, Takahiro; Kinbara, Kazushi; Aida, Takuzo

doi:10.1038/nature04635

Cited by 647 publications

(348 citation statements)

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“…13 Small-molecule machines have been developed that can perform mechanical tasks at the macroscopic level [14][15][16][17][18] and a photoresponsive host molecule has been described that is able to mechanically twist a bound molecular guest. 19 Here we report on a molecular machine that is able to pick up a cargo, reposition it, set it down and release it at a second site approximately 2 nm away from the starting position. The relocation of molecular fragments with a molecular robotic armmaking and breaking covalent bonds in a process during which the substrate is unable to exchange with others in the bulk-is a step towards the controlled manipulation of molecularlevel structures through programmable small-molecule robotics.…”

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confidence: 99%

Pick-up, transport and release of a molecular cargo using a small-molecule robotic arm

et al. 2015

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Modern day factory assembly lines often feature robots that pick up, reposition and connect components in a programmed manner. The idea of manipulating molecular fragments in a similar way has to date only been explored using biological building blocks (DNA). Here we report on a wholly artificial small-molecule robotic arm capable of selectively transporting a molecular cargo in either direction between two spatially distinct, chemically similar, sites on a molecular platform. The arm picks up/releases a 3-mercaptopropanehydrazide cargo by formation/breakage of a disulfide bond, while dynamic hydrazone chemistry controls the cargo binding to the platform. Transport is controlled by selectively inducing conformational and configurational changes within an embedded hydrazone rotary switch that steers the robotic arm. In a three-stage operation 79-85 % of 3-mercaptopropanehydrazide molecules are transported in either (chosen) direction between the two platform sites, without the cargo at any time fully dissociating from the machine nor exchanging with other molecules in the bulk.The mechanical manipulation of matter at atomic length-scales has fascinated scientists since it was proposed by Feynman in 'There's Plenty of Room at the Bottom'.

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confidence: 99%

Pick-up, transport and release of a molecular cargo using a small-molecule robotic arm

et al. 2015

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“…The results obtained in 3@(1a⅐2a) and 4@(1a⅐2a) are summarized in Table 2. Comparison between the exchange rate constant for guest rotation (k) within 1a⅐2a and that for guest release (k Ϫ1 ) from guest@(1a⅐2a) is important in supramolecular system (15,22), because guest rotation might proceed through dissociation of guest from guest@(1a⅐2a) and reencapsulation of guest into 1a⅐2a. For 3c-3e and 3i, the k Ϫ1 values obtained by the 2D EXSY experiments were in the range 0.028-0.085 s Ϫ1 (Table 3, SI Text, and Fig.…”

Section: H Nmr Study: Association Of 1a⅐2a With Guest and Guest Orienmentioning

confidence: 99%

Encapsulated-guest rotation in a self-assembled heterocapsule directed toward a supramolecular gyroscope

Kitagawa

Kobori²,

Yamanaka³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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The self-assembled heterocapsule 1⅐2, which is formed by the hydrogen bonds of tetra(4-pyridyl)-cavitand 1 and tetrakis(4-hydroxyphenyl)-cavitand 2, encapsulates 1 molecule of guests such as 1,4-diacetoxybenzene 3a, 1,4-diacetoxy-2,5-dimethylbenzene 3b, 1,4-diacetoxy-2,5-dialkoxybenzenes (3c, OCH 3; 3d, OC2H5; 3e, OC3H7; 3f, OC 4H9; 3g, OC5H11; 3h, OC6H13; 3i, OC8H17), 1,4-diacetoxy-2,5-difluorobenzene 4a, and 1,4-diacetoxy-2,3-difluorobenzene 4b. The X-ray crystallographic analysis of 3c@(1⅐2) showed that the acetoxy groups at the 1,4-positions of 3c are oriented toward the 2 aromatic cavity ends of 1⅐2 and that 3c can rotate along the long axis of 1⅐2. Thus, the 1⅐2 (stator) with the encapsulation guest (rotator) behaves as a supramolecular gyroscope. A variable temperature (VT) 1 H NMR study in CDCl 3 showed that 3a, 3b, 4a, and 4b within 1⅐2 rotate rapidly even at 218 K, whereas guest rotation is almost inhibited for 3h and 3i even at 323 K. In this respect, 4b with a large dipole moment is a good candidate for the rotator of 1⅐2. For 3c-3g, the enthalpic (⌬H ‡ ) and entropic (⌬S ‡ ) contributions to the free energy of activation (⌬G ‡ ) for the guest-rotational steric barriers within 1⅐2 were obtained from Eyring plots based on line-shape analysis of the VT 1 H NMR spectra. The value of ⌬G ‡ increased in the order 3c < 3d < 3e < 3f < 3g. Thus, the elongation of the alkoxy chains at the 2,5-positions of 3 puts the brakes on guest rotation within 1⅐2.encapsulation ͉ self-assembly M olecular motors with a rotor function have attracted considerable attention in the field of mechanical molecular devices (1, 2). One of the important topics is that of molecular gyroscopes (1, 3), which consist of a rotator with a spinning axis and a stator framework, wherein a rotator is encased and protected by a stator with a frictionless environment. It is expected that rotators with electric dipole moments can rotate unidirectionally in alternating applied electric fields (1,4,5). On the basis of this concept, molecular gyroscopes have so far been synthesized by using several types of covalent-bonded strategies (3, 6-11) and by a metal-coordination strategy such as a metal-centered gyroscope (12, 13) and a self-assembled solid system (14). As an alternative strategy, a self-assembled molecular capsule with an encapsulated guest could behave as a supramolecular gyroscope in which an encapsulated guest is a rotator, and a self-assembled capsule is a stator (15). Molecular self-assembly based on noncovalent interactions offers great advantages in minimization of synthetic effort by use of modular subunits and through thermodynamic equilibration (16). Recently, we have reported the self-assembly of tetra(4-pyridyl)-cavitand 1a and tetrakis(4-hydroxyphenyl)-cavitand 2a (R ϭ (CH 2 ) 6 CH 3 ) into a heterocapsule 1a⅐2a in a rim-to-rim fashion via 4 pyridyl⅐⅐⅐phenol hydrogen bonds, wherein 1 molecule of 1,4-diacetoxybenzene 3a (Y ϭ H) is encapsulated to form a ternary complex 3a@(1a⅐2a), and the exchange of 3a in and out of 1a⅐2a in s...

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“…When implemented in a phase-matched geometry, the dipole emission from each atom interferes constructively to generate a bright HHG beam (8). However, until recently, it was not possible to generate bright, circularly polarized HHG for probing magnetic materials (9) or chiral molecules (10). This is because although atoms still undergo strong-field ionization in circularly polarized fields, the probability of an electron recombining with its parent ion to emit an HHG photon is greatly suppressed (6,11,12).…”

Section: Introductionmentioning

confidence: 99%

Tomographic Reconstruction of Circularly Polarized High Harmonic Fields: 3D Attosecond Metrology

Chen

Tao

Hernández-García

et al. 2016

High-Brightness Sources and Light-Driven Interactions

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Bright, circularly polarized, extreme ultraviolet (EUV) and soft x-ray high-harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. Although the resulting circularly polarized harmonics consist of relatively simple pairs of peaks in the spectral domain, in the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency, and polarization. We extend attosecond metrology techniques to circularly polarized light by simultaneously irradiating a copper surface with circularly polarized high-harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date.

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Mechanical twisting of a guest by a photoresponsive host

Cited by 647 publications

References 21 publications

Pick-up, transport and release of a molecular cargo using a small-molecule robotic arm

Pick-up, transport and release of a molecular cargo using a small-molecule robotic arm

Encapsulated-guest rotation in a self-assembled heterocapsule directed toward a supramolecular gyroscope

Tomographic Reconstruction of Circularly Polarized High Harmonic Fields: 3D Attosecond Metrology

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