The Special Issue on “Photoresponsive Molecular Crystals” is a collection of four original resear... more The Special Issue on “Photoresponsive Molecular Crystals” is a collection of four original research articles dedicated to theoretical and experimental research works providing new insights and experimental findings in the field of photoresponsive crystals [...]
Four fluorinated derivatives of 9-anthracene carboxylic acid (9AC), a molecule that shows a rever... more Four fluorinated derivatives of 9-anthracene carboxylic acid (9AC), a molecule that shows a reversible photomechanical response in its crystal form, have been synthesized and characterized. The spectroscopic properties and crystal structures of 4-fluoro-9anthracene carboxylic acid (4F-9AC), 2-fluoro-9-anthracene carboxylic acid (2F-9AC), 10-fluoro-9-anthracene carboxylic acid (10F-9AC), and 2,6-difluoro-9-anthracene carboxylic acid (2,6DF-9AC) are all very similar to those of 9AC. However, their photomechanical properties vary widely. 405 nm light was used to induce [4 + 4] photodimerization and a mechanical response in crystalline microneedles and ribbons. Both the photodimer dissociation rate and the mechanical recovery varied by more than an order of magnitude, with 4F-9AC exhibiting the most rapid recovery time, on the order of 30 s. Nanoindentation measurements show that this crystal has a slightly reduced elastic modulus and a significantly reduced hardness, making it less brittle than the 9AC crystal. Large 4F-9AC crystals remain intact after irradiation, without fragmenting, while microneedles can undergo more than 100 mechanical bending cycles. Given the similarity of the crystal packing in all five molecules, the improved photomechanical properties must arise from subtle changes in intermolecular interactions or possibly differences in disorder. These results demonstrate that it is possible to significantly improve the properties of photomechanical materials through small modifications of the molecular structure.
A surface plasmon resonance (SPR) imaging system, combined with a microwell gold chip for on-chip... more A surface plasmon resonance (SPR) imaging system, combined with a microwell gold chip for on-chip cell cultivation, was used to monitor protein-protein interactions. In particular, we developed an on-chip microscale cell cultivation system that integrates cell culture and on-chip analysis of protein-protein interactions on a single microwell chip in a time-and labor-saving manner. To assess the performance of this system in the analysis of protein-protein interactions, we conducted a series of protein-protein interaction analyses by measuring the binding of the yeast GAL4 dimerization domain (GAL4DD) to the GAL11 protein (GAL11P). Our system was found to enable the simple and rapid analysis of protein-protein interactions, requiring no special cell culturing equipment or recombinant protein expression prior to the immobilization of the purified proteins onto the chip. Our results demonstrate that the combination of an on-chip cell cultivation system and an SPR imaging system can be a useful tool to study protein-protein interactions without the need for timeconsuming and labor-intensive protein preparation steps as well as fluorescent or other labeling of the interactants.
Anthracene derivatives with a 1,3-butadiene group attached to the 9-position can undergo reversib... more Anthracene derivatives with a 1,3-butadiene group attached to the 9-position can undergo reversible E ↔ Z (trans ↔ cis) photoisomerization reactions, providing a route to new photomechanical materials.
A combined experimental/computational analysis of photomechanical anthracene derivatives reveals ... more A combined experimental/computational analysis of photomechanical anthracene derivatives reveals their kinetic behavior is not simply related to the monomer-photodimer energetics.
Crystalline (E)-4-fluoro-cinnamaldehyde malononitrile undergoes a [2+2] photocycloaddition, leadi... more Crystalline (E)-4-fluoro-cinnamaldehyde malononitrile undergoes a [2+2] photocycloaddition, leading to a robust photomechanical response and improved force generation by nanowire ceramic composites.
Fluorescent switches based on spirocyclic zwitterionic Meisenheimer (SZMC) complexes are stimuli-... more Fluorescent switches based on spirocyclic zwitterionic Meisenheimer (SZMC) complexes are stimuli-responsive organic molecules with application in a variety of areas. To expand their functionality, novel switching mechanisms are herein reported for these systems: (a) acid- and redox-triggered formation of an additional protonation state with distinct optical properties, and (b) solvent-induced fluorescence modulation. We demonstrate that these new features, which enable both multistimuli and multistate operation of SZMC switches, can be exploited in the preparation of smart organic materials: wide-range pH optical probes, electrochromic and electrofluorochromic films, and polymer-based fluorescent detectors of organic liquids.
Angewandte Chemie (International ed. in English), Jan 11, 2018
A surfactant-assisted seeded-growth method is used to form single-crystal platelets composed of 9... more A surfactant-assisted seeded-growth method is used to form single-crystal platelets composed of 9-methylanthracene with two different internal molecular orientations. The more stable form exhibits a photoinduced twisting, as observed previously for 9-methylanthracene microribbons grown by the floating drop method. However, the newly discovered elongated hexagonal platelets undergo a photoinduced rolling-up and unrolling. The ability of the rolled-up cylindrical shape to trap superparamagnetic nanoparticles enables it to be carried along in a magnetic field gradient. The new photoinduced shape change, made possible by a novel surfactant-assisted crystal growth method, opens up the possibility of using light to modulate the crystal translational motion.
Langmuir : the ACS journal of surfaces and colloids, Jan 22, 2017
Dimethyl-2(3-anthracen-9-yl)allylidene)malonate (DMAAM) is a divinylanthracene derivative that ph... more Dimethyl-2(3-anthracen-9-yl)allylidene)malonate (DMAAM) is a divinylanthracene derivative that photoisomerizes between its (E) and (Z) conformations. Crystalline nanowires composed of this molecule undergo a rapid coiling motion when exposed to visible light. In this paper, a variety of experimental techniques are used to investigate the mechanism of this transformation, including powder X-ray diffraction, polarized light microscopy, 1H-NMR and absorption spectroscopy. The results show that the presence of a surfactant like cetyltrimethylammonium bromide (CTAB) accelerates the photochemical reaction rate by at least a factor of 10 within the nanowire and is required to observe the photoinduced coiling. The accelerated reaction facilitates the transition to an amorphous phase composed of reactant and photoproduct, which leads to the rapid, large-scale shape changes that the nanowires undergo. Disruption of the highly packed crystal structure by photoisomerization also enhances the di...
Stable zwitterionic spirocyclic Meisenheimer compounds were synthesized using a one-step reaction... more Stable zwitterionic spirocyclic Meisenheimer compounds were synthesized using a one-step reaction between picric acid and diisopropyl (ZW1) or dicyclohexyl (ZW3) carbodiimide. A solution of these compounds displays intense orange fluorescence upon UV or visible light excitation, which can be quenched or "turned-off" by adding a mole equivalent amount of F- or CN- ions in acetonitrile. Fluorescence is not quenched in the presence of other ions such as Cl-, Br-, I-, NO₂-, NO₃-, or H₂PO₄-. These compounds can therefore be utilized as practical colorimetric and fluorescent probes for monitoring the presence of F- or CN- anions.
Ultraviolet light exposure causes highly branched microcrystals of 4-fluoroanthracene-9-carboxyli... more Ultraviolet light exposure causes highly branched microcrystals of 4-fluoroanthracene-9-carboxylic acid to reversibly deform and manipulate objects on a surface.
Photomechanical molecular crystals can undergo a variety of light-induced motions, including expa... more Photomechanical molecular crystals can undergo a variety of light-induced motions, including expansion, bending, twisting, and jumping. The use of more complex crystal shapes may provide ways to turn these motions into useful work. To generate such shapes, pH-driven reprecipitation has been used to grow branched microcrystals of the anthracene derivative 4-fluoroanthracenecarboxylic acid. When these microcrystals are illuminated with light of λ=405 nm, an intermolecular [4+4] photodimerization reaction drives twisting and bending of the individual branches. These deformations drive a rotation of the overall crystal that can be repeated over multiple exposures to light. The magnitude and direction of this rotation vary because of differences in the crystal shape, but a typical branched crystal undergoes a 50° net rotation after 25 consecutive irradiations for 1 s. The ability of these crystals to undergo ratchet-like rotation is attributed to their chiral shape.
The Special Issue on “Photoresponsive Molecular Crystals” is a collection of four original resear... more The Special Issue on “Photoresponsive Molecular Crystals” is a collection of four original research articles dedicated to theoretical and experimental research works providing new insights and experimental findings in the field of photoresponsive crystals [...]
Four fluorinated derivatives of 9-anthracene carboxylic acid (9AC), a molecule that shows a rever... more Four fluorinated derivatives of 9-anthracene carboxylic acid (9AC), a molecule that shows a reversible photomechanical response in its crystal form, have been synthesized and characterized. The spectroscopic properties and crystal structures of 4-fluoro-9anthracene carboxylic acid (4F-9AC), 2-fluoro-9-anthracene carboxylic acid (2F-9AC), 10-fluoro-9-anthracene carboxylic acid (10F-9AC), and 2,6-difluoro-9-anthracene carboxylic acid (2,6DF-9AC) are all very similar to those of 9AC. However, their photomechanical properties vary widely. 405 nm light was used to induce [4 + 4] photodimerization and a mechanical response in crystalline microneedles and ribbons. Both the photodimer dissociation rate and the mechanical recovery varied by more than an order of magnitude, with 4F-9AC exhibiting the most rapid recovery time, on the order of 30 s. Nanoindentation measurements show that this crystal has a slightly reduced elastic modulus and a significantly reduced hardness, making it less brittle than the 9AC crystal. Large 4F-9AC crystals remain intact after irradiation, without fragmenting, while microneedles can undergo more than 100 mechanical bending cycles. Given the similarity of the crystal packing in all five molecules, the improved photomechanical properties must arise from subtle changes in intermolecular interactions or possibly differences in disorder. These results demonstrate that it is possible to significantly improve the properties of photomechanical materials through small modifications of the molecular structure.
A surface plasmon resonance (SPR) imaging system, combined with a microwell gold chip for on-chip... more A surface plasmon resonance (SPR) imaging system, combined with a microwell gold chip for on-chip cell cultivation, was used to monitor protein-protein interactions. In particular, we developed an on-chip microscale cell cultivation system that integrates cell culture and on-chip analysis of protein-protein interactions on a single microwell chip in a time-and labor-saving manner. To assess the performance of this system in the analysis of protein-protein interactions, we conducted a series of protein-protein interaction analyses by measuring the binding of the yeast GAL4 dimerization domain (GAL4DD) to the GAL11 protein (GAL11P). Our system was found to enable the simple and rapid analysis of protein-protein interactions, requiring no special cell culturing equipment or recombinant protein expression prior to the immobilization of the purified proteins onto the chip. Our results demonstrate that the combination of an on-chip cell cultivation system and an SPR imaging system can be a useful tool to study protein-protein interactions without the need for timeconsuming and labor-intensive protein preparation steps as well as fluorescent or other labeling of the interactants.
Anthracene derivatives with a 1,3-butadiene group attached to the 9-position can undergo reversib... more Anthracene derivatives with a 1,3-butadiene group attached to the 9-position can undergo reversible E ↔ Z (trans ↔ cis) photoisomerization reactions, providing a route to new photomechanical materials.
A combined experimental/computational analysis of photomechanical anthracene derivatives reveals ... more A combined experimental/computational analysis of photomechanical anthracene derivatives reveals their kinetic behavior is not simply related to the monomer-photodimer energetics.
Crystalline (E)-4-fluoro-cinnamaldehyde malononitrile undergoes a [2+2] photocycloaddition, leadi... more Crystalline (E)-4-fluoro-cinnamaldehyde malononitrile undergoes a [2+2] photocycloaddition, leading to a robust photomechanical response and improved force generation by nanowire ceramic composites.
Fluorescent switches based on spirocyclic zwitterionic Meisenheimer (SZMC) complexes are stimuli-... more Fluorescent switches based on spirocyclic zwitterionic Meisenheimer (SZMC) complexes are stimuli-responsive organic molecules with application in a variety of areas. To expand their functionality, novel switching mechanisms are herein reported for these systems: (a) acid- and redox-triggered formation of an additional protonation state with distinct optical properties, and (b) solvent-induced fluorescence modulation. We demonstrate that these new features, which enable both multistimuli and multistate operation of SZMC switches, can be exploited in the preparation of smart organic materials: wide-range pH optical probes, electrochromic and electrofluorochromic films, and polymer-based fluorescent detectors of organic liquids.
Angewandte Chemie (International ed. in English), Jan 11, 2018
A surfactant-assisted seeded-growth method is used to form single-crystal platelets composed of 9... more A surfactant-assisted seeded-growth method is used to form single-crystal platelets composed of 9-methylanthracene with two different internal molecular orientations. The more stable form exhibits a photoinduced twisting, as observed previously for 9-methylanthracene microribbons grown by the floating drop method. However, the newly discovered elongated hexagonal platelets undergo a photoinduced rolling-up and unrolling. The ability of the rolled-up cylindrical shape to trap superparamagnetic nanoparticles enables it to be carried along in a magnetic field gradient. The new photoinduced shape change, made possible by a novel surfactant-assisted crystal growth method, opens up the possibility of using light to modulate the crystal translational motion.
Langmuir : the ACS journal of surfaces and colloids, Jan 22, 2017
Dimethyl-2(3-anthracen-9-yl)allylidene)malonate (DMAAM) is a divinylanthracene derivative that ph... more Dimethyl-2(3-anthracen-9-yl)allylidene)malonate (DMAAM) is a divinylanthracene derivative that photoisomerizes between its (E) and (Z) conformations. Crystalline nanowires composed of this molecule undergo a rapid coiling motion when exposed to visible light. In this paper, a variety of experimental techniques are used to investigate the mechanism of this transformation, including powder X-ray diffraction, polarized light microscopy, 1H-NMR and absorption spectroscopy. The results show that the presence of a surfactant like cetyltrimethylammonium bromide (CTAB) accelerates the photochemical reaction rate by at least a factor of 10 within the nanowire and is required to observe the photoinduced coiling. The accelerated reaction facilitates the transition to an amorphous phase composed of reactant and photoproduct, which leads to the rapid, large-scale shape changes that the nanowires undergo. Disruption of the highly packed crystal structure by photoisomerization also enhances the di...
Stable zwitterionic spirocyclic Meisenheimer compounds were synthesized using a one-step reaction... more Stable zwitterionic spirocyclic Meisenheimer compounds were synthesized using a one-step reaction between picric acid and diisopropyl (ZW1) or dicyclohexyl (ZW3) carbodiimide. A solution of these compounds displays intense orange fluorescence upon UV or visible light excitation, which can be quenched or "turned-off" by adding a mole equivalent amount of F- or CN- ions in acetonitrile. Fluorescence is not quenched in the presence of other ions such as Cl-, Br-, I-, NO₂-, NO₃-, or H₂PO₄-. These compounds can therefore be utilized as practical colorimetric and fluorescent probes for monitoring the presence of F- or CN- anions.
Ultraviolet light exposure causes highly branched microcrystals of 4-fluoroanthracene-9-carboxyli... more Ultraviolet light exposure causes highly branched microcrystals of 4-fluoroanthracene-9-carboxylic acid to reversibly deform and manipulate objects on a surface.
Photomechanical molecular crystals can undergo a variety of light-induced motions, including expa... more Photomechanical molecular crystals can undergo a variety of light-induced motions, including expansion, bending, twisting, and jumping. The use of more complex crystal shapes may provide ways to turn these motions into useful work. To generate such shapes, pH-driven reprecipitation has been used to grow branched microcrystals of the anthracene derivative 4-fluoroanthracenecarboxylic acid. When these microcrystals are illuminated with light of λ=405 nm, an intermolecular [4+4] photodimerization reaction drives twisting and bending of the individual branches. These deformations drive a rotation of the overall crystal that can be repeated over multiple exposures to light. The magnitude and direction of this rotation vary because of differences in the crystal shape, but a typical branched crystal undergoes a 50° net rotation after 25 consecutive irradiations for 1 s. The ability of these crystals to undergo ratchet-like rotation is attributed to their chiral shape.
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