13 research outputs found
Multistate Photochromism of 1‑Phenylnaphthalene-Bridged Imidazole Dimer That Has Three Colorless Isomers and Two Colored Isomers
A new type of the bridged imidazole
dimer with a 1-phenylnaphthalene moiety that bridges two diphenylimidazole
units at the 2- and 2′-positions was synthesized and the photochemical
and thermochemical properties were investigated. This molecule shows
unique multistate photochromism, in which the stable colorless 1,2′-isomers
A and B photochemically isomerize to the colorless 2,2′-isomer
through the short-lived biradical with a half-life of 180 ns at 25
°C. The 2,2′-isomer thermally returns to the 1,2′-isomers
A and B through the colored isomer at elevated temperatures. The 1,2′-isomers
A and B, the 2,2′-isomer, and the colored isomer were isolated,
and their molecular structures were determined by X-ray crystallographic
analysis. These isomers are stable at room temperature and can be
almost fully converted to the 2,2′-isomer by light irradiation.
This study serves the useful strategy for the molecular design of
a new type of negative photochromic molecules applicable to switch
molecular properties by visible light irradiation
Multistate Photochromism of 1‑Phenylnaphthalene-Bridged Imidazole Dimer That Has Three Colorless Isomers and Two Colored Isomers
A new type of the bridged imidazole
dimer with a 1-phenylnaphthalene moiety that bridges two diphenylimidazole
units at the 2- and 2′-positions was synthesized and the photochemical
and thermochemical properties were investigated. This molecule shows
unique multistate photochromism, in which the stable colorless 1,2′-isomers
A and B photochemically isomerize to the colorless 2,2′-isomer
through the short-lived biradical with a half-life of 180 ns at 25
°C. The 2,2′-isomer thermally returns to the 1,2′-isomers
A and B through the colored isomer at elevated temperatures. The 1,2′-isomers
A and B, the 2,2′-isomer, and the colored isomer were isolated,
and their molecular structures were determined by X-ray crystallographic
analysis. These isomers are stable at room temperature and can be
almost fully converted to the 2,2′-isomer by light irradiation.
This study serves the useful strategy for the molecular design of
a new type of negative photochromic molecules applicable to switch
molecular properties by visible light irradiation
Multistate Photochromism of 1‑Phenylnaphthalene-Bridged Imidazole Dimer That Has Three Colorless Isomers and Two Colored Isomers
A new type of the bridged imidazole
dimer with a 1-phenylnaphthalene moiety that bridges two diphenylimidazole
units at the 2- and 2′-positions was synthesized and the photochemical
and thermochemical properties were investigated. This molecule shows
unique multistate photochromism, in which the stable colorless 1,2′-isomers
A and B photochemically isomerize to the colorless 2,2′-isomer
through the short-lived biradical with a half-life of 180 ns at 25
°C. The 2,2′-isomer thermally returns to the 1,2′-isomers
A and B through the colored isomer at elevated temperatures. The 1,2′-isomers
A and B, the 2,2′-isomer, and the colored isomer were isolated,
and their molecular structures were determined by X-ray crystallographic
analysis. These isomers are stable at room temperature and can be
almost fully converted to the 2,2′-isomer by light irradiation.
This study serves the useful strategy for the molecular design of
a new type of negative photochromic molecules applicable to switch
molecular properties by visible light irradiation
Multistate Photochromism of 1‑Phenylnaphthalene-Bridged Imidazole Dimer That Has Three Colorless Isomers and Two Colored Isomers
A new type of the bridged imidazole
dimer with a 1-phenylnaphthalene moiety that bridges two diphenylimidazole
units at the 2- and 2′-positions was synthesized and the photochemical
and thermochemical properties were investigated. This molecule shows
unique multistate photochromism, in which the stable colorless 1,2′-isomers
A and B photochemically isomerize to the colorless 2,2′-isomer
through the short-lived biradical with a half-life of 180 ns at 25
°C. The 2,2′-isomer thermally returns to the 1,2′-isomers
A and B through the colored isomer at elevated temperatures. The 1,2′-isomers
A and B, the 2,2′-isomer, and the colored isomer were isolated,
and their molecular structures were determined by X-ray crystallographic
analysis. These isomers are stable at room temperature and can be
almost fully converted to the 2,2′-isomer by light irradiation.
This study serves the useful strategy for the molecular design of
a new type of negative photochromic molecules applicable to switch
molecular properties by visible light irradiation
Multistate Photochromism of 1‑Phenylnaphthalene-Bridged Imidazole Dimer That Has Three Colorless Isomers and Two Colored Isomers
A new type of the bridged imidazole
dimer with a 1-phenylnaphthalene moiety that bridges two diphenylimidazole
units at the 2- and 2′-positions was synthesized and the photochemical
and thermochemical properties were investigated. This molecule shows
unique multistate photochromism, in which the stable colorless 1,2′-isomers
A and B photochemically isomerize to the colorless 2,2′-isomer
through the short-lived biradical with a half-life of 180 ns at 25
°C. The 2,2′-isomer thermally returns to the 1,2′-isomers
A and B through the colored isomer at elevated temperatures. The 1,2′-isomers
A and B, the 2,2′-isomer, and the colored isomer were isolated,
and their molecular structures were determined by X-ray crystallographic
analysis. These isomers are stable at room temperature and can be
almost fully converted to the 2,2′-isomer by light irradiation.
This study serves the useful strategy for the molecular design of
a new type of negative photochromic molecules applicable to switch
molecular properties by visible light irradiation
Remarkable Acceleration for Back-Reaction of a Fast Photochromic Molecule
We demonstrate that photochromism based on light-driven reversible C−N single bond cleavage can enable rapid coloration upon UV light irradiation and successive fast thermal back-reaction within tens of microseconds at room temperature. According to Marcus theory, the thermal back-reaction would be accelerated with increasing Δ<i>G</i><sup>0</sup>, which is closely linked to the decrease in Δ<i>G</i><sup>‡</sup>. We have considered that the Δ<i>G</i><sup>0</sup> of the thermal back-reaction could be enlarged by destabilizing the colored species and designed pseudogem-DPI-PI[2.2]PC, with a [2.2]paracyclophane moiety that couples diphenylimidazole and phenanthroimidazole groups. The present study demonstrates that controlling the stability of the biradical state is effective in accelerating the thermal back-reaction for the photochromic [2.2]paracyclophane-bridged imidazole dimer
Remarkable Acceleration for Back-Reaction of a Fast Photochromic Molecule
We demonstrate that photochromism based on light-driven reversible C−N single bond cleavage can enable rapid coloration upon UV light irradiation and successive fast thermal back-reaction within tens of microseconds at room temperature. According to Marcus theory, the thermal back-reaction would be accelerated with increasing Δ<i>G</i><sup>0</sup>, which is closely linked to the decrease in Δ<i>G</i><sup>‡</sup>. We have considered that the Δ<i>G</i><sup>0</sup> of the thermal back-reaction could be enlarged by destabilizing the colored species and designed pseudogem-DPI-PI[2.2]PC, with a [2.2]paracyclophane moiety that couples diphenylimidazole and phenanthroimidazole groups. The present study demonstrates that controlling the stability of the biradical state is effective in accelerating the thermal back-reaction for the photochromic [2.2]paracyclophane-bridged imidazole dimer
Unusual Negative Photochromism via a Short-Lived Imidazolyl Radical of 1,1′-Binaphthyl-Bridged Imidazole Dimer
We have synthesized a new photochromic
compound that exhibits unusual
negative photoÂchromism, in which the stable colored species
photoÂchemically converts into the metastable colorless species
via a short-lived radical. This compound has a 1,1′-biÂnaphthyl
moiety bridging the two diphenylÂimidÂazole units. Its photoÂchemical
properties were investigated by nanosecond laser flash photolysis.
The colored species isomerizes to the colorless species upon exposure
to visible light and thermally returns to the original colored species
within 20 min at room temperature. Moreover, the photodecoloration
reaction proceeds via a short-lived radical with a half-life of 9.4
μs in benzene at room temperature. Both the colored and colorless
species show the photoÂinduced homolytic bond cleavage reaction
of the C–N bond between the nitrogen atom of the imidÂazole
ring and the carbon atom of the 1-position of the 1,1′-biÂnaphthyl
moiety and that of the C–C bond between each of the carbon
atoms of the 2-position of the imidÂazole ring, respectively,
followed by their formation by rapid radical coupling
Unusual Negative Photochromism via a Short-Lived Imidazolyl Radical of 1,1′-Binaphthyl-Bridged Imidazole Dimer
We have synthesized a new photochromic
compound that exhibits unusual
negative photoÂchromism, in which the stable colored species
photoÂchemically converts into the metastable colorless species
via a short-lived radical. This compound has a 1,1′-biÂnaphthyl
moiety bridging the two diphenylÂimidÂazole units. Its photoÂchemical
properties were investigated by nanosecond laser flash photolysis.
The colored species isomerizes to the colorless species upon exposure
to visible light and thermally returns to the original colored species
within 20 min at room temperature. Moreover, the photodecoloration
reaction proceeds via a short-lived radical with a half-life of 9.4
μs in benzene at room temperature. Both the colored and colorless
species show the photoÂinduced homolytic bond cleavage reaction
of the C–N bond between the nitrogen atom of the imidÂazole
ring and the carbon atom of the 1-position of the 1,1′-biÂnaphthyl
moiety and that of the C–C bond between each of the carbon
atoms of the 2-position of the imidÂazole ring, respectively,
followed by their formation by rapid radical coupling
Unusual Negative Photochromism via a Short-Lived Imidazolyl Radical of 1,1′-Binaphthyl-Bridged Imidazole Dimer
We have synthesized a new photochromic
compound that exhibits unusual
negative photoÂchromism, in which the stable colored species
photoÂchemically converts into the metastable colorless species
via a short-lived radical. This compound has a 1,1′-biÂnaphthyl
moiety bridging the two diphenylÂimidÂazole units. Its photoÂchemical
properties were investigated by nanosecond laser flash photolysis.
The colored species isomerizes to the colorless species upon exposure
to visible light and thermally returns to the original colored species
within 20 min at room temperature. Moreover, the photodecoloration
reaction proceeds via a short-lived radical with a half-life of 9.4
μs in benzene at room temperature. Both the colored and colorless
species show the photoÂinduced homolytic bond cleavage reaction
of the C–N bond between the nitrogen atom of the imidÂazole
ring and the carbon atom of the 1-position of the 1,1′-biÂnaphthyl
moiety and that of the C–C bond between each of the carbon
atoms of the 2-position of the imidÂazole ring, respectively,
followed by their formation by rapid radical coupling