A Diarylethene with Two Nitronyl Nitroxides: Photoswitching of Intramolecular Magnetic Interaction

A diarylethene having two nitronyl nitroxides, 1,2-bis[6-(1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolin-2-yl)-2-methyl-1-benzothiophen-3-yl]hexafluorocyclopentene (2a), was synthesized in an attempt to control the intramolecular magnetic interaction by photoirradiation. The photochemical conversions from open-ring isomer 2a to closed-ring isomer 2b and from 2b to 2a were both almost 100%. Magnetic measurement revealed the antiferromagnetic interaction between two nitronyl nitroxides remarkably increased from 2J/kB = −2.2 K to 2J/kB = −11.6 K when the diarylethene spin coupler was switched from the open-ring isomer 2a to the closed-ring isomer 2b. ESR measurements were also carried out for both 2a and 2b in benzene solutions at room temperature and in MTHF solid solutions at cryogenic temperature. Both ESR and magnetic measurement indicated that the intramolecular interaction was switched by the photochromic spin coupler

Evaluation of the β Value of the Phenylene Unit by Probing Exchange Interaction between Two Nitroxides

Oligophenylene molecular rods with bicyclo[2.2.2]octane having two nitronyl nitroxide radicals were synthesized to investigate the decay constant of p-phenylene. By the measurement and simulation of the ESR spectra of the biradicals with different rod length, it was found that the exchange interaction was decreased with the decay constant β of 0.51 ± 0.01 Å−1. This result indicates that the spin−spin exchange interaction between neutral radicals has a decay constant similar to the molecular conductance

A Diarylethene with Two Nitronyl Nitroxides: Photoswitching of Intramolecular Magnetic Interaction

A diarylethene having two nitronyl nitroxides, 1,2-bis[6-(1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolin-2-yl)-2-methyl-1-benzothiophen-3-yl]hexafluorocyclopentene (2a), was synthesized in an attempt to control the intramolecular magnetic interaction by photoirradiation. The photochemical conversions from open-ring isomer 2a to closed-ring isomer 2b and from 2b to 2a were both almost 100%. Magnetic measurement revealed the antiferromagnetic interaction between two nitronyl nitroxides remarkably increased from 2J/kB = −2.2 K to 2J/kB = −11.6 K when the diarylethene spin coupler was switched from the open-ring isomer 2a to the closed-ring isomer 2b. ESR measurements were also carried out for both 2a and 2b in benzene solutions at room temperature and in MTHF solid solutions at cryogenic temperature. Both ESR and magnetic measurement indicated that the intramolecular interaction was switched by the photochromic spin coupler

A Diarylethene with Two Nitronyl Nitroxides: Photoswitching of Intramolecular Magnetic Interaction

A diarylethene having two nitronyl nitroxides, 1,2-bis[6-(1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolin-2-yl)-2-methyl-1-benzothiophen-3-yl]hexafluorocyclopentene (2a), was synthesized in an attempt to control the intramolecular magnetic interaction by photoirradiation. The photochemical conversions from open-ring isomer 2a to closed-ring isomer 2b and from 2b to 2a were both almost 100%. Magnetic measurement revealed the antiferromagnetic interaction between two nitronyl nitroxides remarkably increased from 2J/kB = −2.2 K to 2J/kB = −11.6 K when the diarylethene spin coupler was switched from the open-ring isomer 2a to the closed-ring isomer 2b. ESR measurements were also carried out for both 2a and 2b in benzene solutions at room temperature and in MTHF solid solutions at cryogenic temperature. Both ESR and magnetic measurement indicated that the intramolecular interaction was switched by the photochromic spin coupler

Structural Colored Balloons Responsive to pH Change

Structural colored balloons (SCBs) composed of poly­(4-vinylpyridine-<i>co</i>-styrene) (P4VP-PS) exhibited a pH-controlled structural color change in the presence and absence of <i>p</i>-toluenesulfonic acid. The diameter of the SCBs increased and decreased under acidic and neutral conditions, respectively. The different colors exhibited at different pH values supposedly resulted from a change in the shell thickness not only due to the change in the diameter of the SCBs but also due to the uptake of <i>p</i>-toluenesulfonic acid to the pyridyl side chain of P4VP-PS

Structural Colored Balloon Composed of Temperature-Responsive Polymers Showing LCST Behavior

Structural colored balloons (SCBs) consisting of polymer thin film developed structural color by thin-layer interference on the shell. Thermoresponsive SCBs were prepared with poly­(diethylene glycol monomethyl ether methacrylate)-co-poly­(N-phenylacrylamide), which shows lower critical solution temperature (LCST) behavior. When cooling gelatin aqueous solution in which osmotic pressure was not operated, only hydration of the copolymer progressed due to LCST transition. The optical path length of the SCB increased due to swelling by water and subsequently decreased due to dissolution. The structural color changed according to the change in optical path length. In cold pure water, in addition to the hydration, osmotic pressure was operated to induce an influx of the outer solvent and the resulting diameter change also affected the shell thickness. The structural color change was analyzed to reveal that the dissolution of the polymer had significant effect on the developed structural color

Structural Colored Balloon Composed of Temperature-Responsive Polymers Showing LCST Behavior

Structural colored balloons (SCBs) consisting of polymer thin film developed structural color by thin-layer interference on the shell. Thermoresponsive SCBs were prepared with poly­(diethylene glycol monomethyl ether methacrylate)-co-poly­(N-phenylacrylamide), which shows lower critical solution temperature (LCST) behavior. When cooling gelatin aqueous solution in which osmotic pressure was not operated, only hydration of the copolymer progressed due to LCST transition. The optical path length of the SCB increased due to swelling by water and subsequently decreased due to dissolution. The structural color changed according to the change in optical path length. In cold pure water, in addition to the hydration, osmotic pressure was operated to induce an influx of the outer solvent and the resulting diameter change also affected the shell thickness. The structural color change was analyzed to reveal that the dissolution of the polymer had significant effect on the developed structural color

Structural Colored Balloon Composed of Temperature-Responsive Polymers Showing LCST Behavior

Structural colored balloons (SCBs) consisting of polymer thin film developed structural color by thin-layer interference on the shell. Thermoresponsive SCBs were prepared with poly­(diethylene glycol monomethyl ether methacrylate)-co-poly­(N-phenylacrylamide), which shows lower critical solution temperature (LCST) behavior. When cooling gelatin aqueous solution in which osmotic pressure was not operated, only hydration of the copolymer progressed due to LCST transition. The optical path length of the SCB increased due to swelling by water and subsequently decreased due to dissolution. The structural color changed according to the change in optical path length. In cold pure water, in addition to the hydration, osmotic pressure was operated to induce an influx of the outer solvent and the resulting diameter change also affected the shell thickness. The structural color change was analyzed to reveal that the dissolution of the polymer had significant effect on the developed structural color

Structural Colored Balloon Composed of Temperature-Responsive Polymers Showing LCST Behavior

Structural colored balloons (SCBs) consisting of polymer thin film developed structural color by thin-layer interference on the shell. Thermoresponsive SCBs were prepared with poly­(diethylene glycol monomethyl ether methacrylate)-co-poly­(N-phenylacrylamide), which shows lower critical solution temperature (LCST) behavior. When cooling gelatin aqueous solution in which osmotic pressure was not operated, only hydration of the copolymer progressed due to LCST transition. The optical path length of the SCB increased due to swelling by water and subsequently decreased due to dissolution. The structural color changed according to the change in optical path length. In cold pure water, in addition to the hydration, osmotic pressure was operated to induce an influx of the outer solvent and the resulting diameter change also affected the shell thickness. The structural color change was analyzed to reveal that the dissolution of the polymer had significant effect on the developed structural color

Evaluation of the β Value of the Phenylene Ethynylene Unit by Probing the Exchange Interaction between Two Nitronyl Nitroxides

A series of nitronyl nitroxide radicals having different lengths of phenylene ethynylene molecular wire were synthesized to investigate the decay constant of p-phenylene ethynylene. By the measurement and simulation of the ESR spectra of the biradicals, it was found that the exchange interaction decreased with a decay constant (β) of 0.39 Å–1 as the length of the molecule increased. This result indicates that the spin–spin exchange interaction between neutral radicals has a decay constant similar to that of the molecular conductance. This value of the decay constant indicates that a hopping mechanism does not take place in the measurement of the exchange interaction between neutral radicals even when the molecular wire has enough length to show hopping conduction of electrons