Regular Two-Dimensional Arrays of Surface-Mounted Molecular Switches: Switching Monitored by UV–vis and NMR Spectroscopy

Hurtado, Carina Santos; Bastien, Guillaume; Mašát, Milan; Štoček, Jakub Radek; Dračínský, Martin; Rončević, Igor; Cı́sařová, Ivana; Rogers, Charles T.; Kaleta, Jiřı́

doi:10.1021/jacs.0c01753

Cited by 17 publications

(18 citation statements)

References 41 publications

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“… [13,14] . They have been thoroughly investigated not only i) in solution [3–5,13–15] and ii) in solid‐state as ordered 3‐D materials, [16–22] but also on iii) interfaces (solid‐liquid, solid‐gas, liquid‐gas), mostly in the form of regular 2‐D arrays [6,10,23–29] . In particular, using interfaces is highly attractive as it combines the ability of molecular machines to freely operate, which is characteristic for systems in solution, with a high order typical for crystalline materials.…”

Section: Introductionmentioning

confidence: 99%

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Triptycene‐Based Molecular Rods for Langmuir‐Blodgett Monolayers

et al. 2022

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Herein we introduce fully modular synthesis leading to three representative examples of rigid molecular rods that are intended to form sturdy monolayers on various surfaces. These molecules contain two triptycene units that are designed to interlock into a compact “double‐decker” structure. Two of the three final products provided suitable crystals for X‐ray diffraction (analyzed on synchrotron), allowing deeper insight into packing in the 3‐D crystal lattice. The acidity of all three compounds were determined by capillary electrophoresis, and the pKa values ranged between 2.06‐2.53. All three rigid rods easily formed Langmuir‐Blodgett monolayers (LBMs) on the water‐air interfaces, with the area per molecule equal to 55–59 Å2/molecule, suggesting tight intermolecular packing. The thickness of all three films reached ∼19 Å after transfer to a gold (111) surface, meaning that individual molecules are tilted maximally 38° from the axis perpendicular to the surface. The structure of one of these films on a gold (111) surface was visualized by AFM. These geometrically unique molecules represent promising platforms with a wide scope of applicability in the supramolecular architecture.

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Section: Introductionmentioning

confidence: 99%

“…We are particularly interested in triptycene‐based stands, since these versatile systems are easily available in multigram quantities, are highly robust, allow numerous chemical modifications, and can be easily adjusted to various surfaces [25–28,31–33] …”

Section: Introductionmentioning

confidence: 99%

Triptycene‐Based Molecular Rods for Langmuir‐Blodgett Monolayers

et al. 2022

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“…In pursuit of this balance, a range of different strategies have been developed to accommodate the conformational changes associated with photoswitching under confinement . These strategies include diluting densely packed monolayers of photoswitches with shorter molecules, , decorating photoswitches with spacer groups, , and confining them on curved substrates, within porous solids, , within the spaces between aggregated nanoparticles, or within the cavities of flexible coordination cages . To compare the behaviors of photoswitchable molecules within different confined environments, we have organized this Account according to the type of photoswitch, roughly in order of increasing demand for conformational freedom.…”

Section: Introductionmentioning

confidence: 99%

Molecular Photoswitching in Confined Spaces

2020

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Conspectus In nature, light is harvested by photoactive proteins to drive a range of biological processes, including photosynthesis, phototaxis, vision, and ultimately life. Bacteriorhodopsin, for example, is a protein embedded within archaeal cell membranes that binds the chromophore retinal within its hydrophobic pocket. Exposure to light triggers regioselective photoisomerization of the confined retinal, which in turn initiates a cascade of conformational changes within the protein, triggering proton flux against the concentration gradient, providing the microorganisms with the energy to live. We are inspired by these functions in nature to harness light energy using synthetic photoswitches under confinement. Like retinal, synthetic photoswitches require some degree of conformational flexibility to isomerize. In nature, the conformational change associated with retinal isomerization is accommodated by the structural flexibility of the opsin host, yet it results in steric communication between the chromophore and the protein. Similarly, we strive to design systems wherein isomerization of confined photoswitches results in steric communication between a photoswitch and its confining environment. To achieve this aim, a balance must be struck between molecular crowding and conformational freedom under confinement: too much crowding prevents switching, whereas too much freedom resembles switching of isolated molecules in solution, preventing communication. In this Account, we discuss five classes of synthetic light-switchable compoundsdiarylethenes, anthracenes, azobenzenes, spiropyrans, and donor–acceptor Stenhouse adductscomparing their behaviors under confinement and in solution. The environments employed to confine these photoswitches are diverse, ranging from planar surfaces to nanosized cavities within coordination cages, nanoporous frameworks, and nanoparticle aggregates. The trends that emerge are primarily dependent on the nature of the photoswitch and not on the material used for confinement. In general, we find that photoswitches requiring less conformational freedom for switching are, as expected, more straightforward to isomerize reversibly under confinement. Because these compounds undergo only small structural changes upon isomerization, however, switching does not propagate into communication with their environment. Conversely, photoswitches that require more conformational freedom are more challenging to switch under confinement but also can influence system-wide behavior. Although we are primarily interested in the effects of geometric constraints on photoswitching under confinement, additional effects inevitably emerge when a compound is removed from solution and placed within a new, more crowded environment. For instance, we have found that compounds that convert to zwitterionic isomers upon light irradiation often experience stabilization of these forms under confinement. This effect results from the mutual stabilization of zwitterions that are brought into close proximity on surfaces or with...

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“…The chemistry of bicyclo[1.1.1]pentanes (BCPs) has been experiencing a huge boom in recent years, as clearly demonstrated by numerous articles and reviews. − Much effort has been directed into the development of modern synthetic techniques that allow incorporation of these cages into complex systems using various cross-coupling reactions on the bridgehead carbon atoms. − Such 1,3-disubstituted BCPs thus not only appeared as the biologically active substances − but also became important players in the field of supramolecular chemistry. − …”

Section: Introductionmentioning

confidence: 99%

Polyhalogenated Bicyclo[1.1.1]pentane-1,3-dicarboxylic Acids

Rončević

Dračínský

et al. 2021

J. Org. Chem.

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Herein we report the highly selective radical chlorination of 2,2-difluorobicyclo[1.1.1]pentane-1,3-dicarboxylic acid. Together with radical hydrodechlorination by TMS3SiH, four new bicyclo[1.1.1]pentane cages carrying two fluorine and one to three chlorine atoms in bridge positions have been obtained. The exact positions of all halogen atoms have been confirmed by X-ray diffraction. The acidity constants (pK a) for all new derivatives have been determined by capillary electrophoresis, and these experimental values show excellent agreement with pK as predicted by DFT methods. Extensive DFT calculations have been used to rationalize the selective formation of four out of nine possible F2Cl1–4 isomers of bridge-halogenated bicyclo[1.1.1]pentanes and to obtain relative strain energies for all possible isomers.

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Regular Two-Dimensional Arrays of Surface-Mounted Molecular Switches: Switching Monitored by UV–vis and NMR Spectroscopy

Cited by 17 publications

References 41 publications

Triptycene‐Based Molecular Rods for Langmuir‐Blodgett Monolayers

Triptycene‐Based Molecular Rods for Langmuir‐Blodgett Monolayers

Molecular Photoswitching in Confined Spaces

Polyhalogenated Bicyclo[1.1.1]pentane-1,3-dicarboxylic Acids

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