Reversible Laser-Induced Bending of Pseudorotaxane Crystals

This study investigated the dynamic photoresponse of pseudorotaxane crystals with azobenzene and ferrocenyl groups in the axle component. X-ray crystallography showed pseudorotaxanes with a methylazobenzene group and a dibromophenylene ring in the cyclic component to exhibit twisting of the <i>trans</i>-azobenzene groups at torsion angles of 17° and 38°, respectively. Repeated alternating laser irradiation of the crystals at 360 and 445 nm produced bending of 20–30° in opposite directions, with no evidence of decay. Under 445 nm irradiation, bending took place within 0.3 s. A crystal of nonsubstituted pseudorotaxane showed bending of only 2° under 360 nm irradiation due to multiple π–π interactions between the planar <i>trans</i>-azobenzene groups. The pseudorotaxane crystals have two chromophores, bent rapidly and reversibly on irradiation at rates depending on the molecular structure

Reversible Laser-Induced Bending of Pseudorotaxane Crystals

This study investigated the dynamic photoresponse of pseudorotaxane crystals with azobenzene and ferrocenyl groups in the axle component. X-ray crystallography showed pseudorotaxanes with a methylazobenzene group and a dibromophenylene ring in the cyclic component to exhibit twisting of the <i>trans</i>-azobenzene groups at torsion angles of 17° and 38°, respectively. Repeated alternating laser irradiation of the crystals at 360 and 445 nm produced bending of 20–30° in opposite directions, with no evidence of decay. Under 445 nm irradiation, bending took place within 0.3 s. A crystal of nonsubstituted pseudorotaxane showed bending of only 2° under 360 nm irradiation due to multiple π–π interactions between the planar <i>trans</i>-azobenzene groups. The pseudorotaxane crystals have two chromophores, bent rapidly and reversibly on irradiation at rates depending on the molecular structure

Thermally-Induced Phase Transition of Pseudorotaxane Crystals: Changes in Conformation and Interaction of the Molecules and Optical Properties of the Crystals

This paper presents a pseudorotaxane that acts as a thermally driven molecular switch in the single-crystal state. Crystals of the cationic pseudorotaxane consisting of dibenzo[24]­crown-8 (DB24C8) and <i>N</i>-(xylylammonium)-methylferrocene as the cyclic and axle component molecules, respectively, undergo crystalline-phase transition at 128 °C with heating and 116 °C with cooling, according to differential-scanning-calorimetry measurements. X-ray crystallographic analyses revealed that the phase transition was accompanied by rotation of the 4-methylphenyl group of the axle component molecule and a simultaneous shift in the position of the PF₆^– counteranion. Crystalline phase transition changes the conformation and position of the DB24C8 molecule relative to the ammonium cation partially; the interaction between the cyclic component and the PF₆^– anion in the crystal changes to a greater extent. Moreover, there are changes in the vibration angle (θ) and birefringence (Δ<i>n</i>) on the (001) face of the crystal transitionally; θ is rotated by +12°, and Δ<i>n</i> is decreased from 0.070 to 0.059 upon heating across the phase transition temperature. The phase transition and accompanying change in the optical properties of the crystal occur reversibly and repeatedly upon heating and cooling processes. The switching rotation of the aromatic plane of the molecule induces a change in the optical anisotropy of the crystal, which is regarded as a demonstration of a new type of optical crystal. Partial replacement of the PF₆^– anion with the bulkier AsF₆^– anion forms crystals with similar crystallographic parameters. An increase in the AsF₆^– content decreases the reversible-phase-transition temperature gradually down to 99 °C (<i>T</i>_end) and 68 °C (<i>T</i>_exo) ([AsF₆^–]:[PF₆^–] = 0.4:0.6)

Thermally-Induced Phase Transition of Pseudorotaxane Crystals: Changes in Conformation and Interaction of the Molecules and Optical Properties of the Crystals

This paper presents a pseudorotaxane that acts as a thermally driven molecular switch in the single-crystal state. Crystals of the cationic pseudorotaxane consisting of dibenzo[24]­crown-8 (DB24C8) and <i>N</i>-(xylylammonium)-methylferrocene as the cyclic and axle component molecules, respectively, undergo crystalline-phase transition at 128 °C with heating and 116 °C with cooling, according to differential-scanning-calorimetry measurements. X-ray crystallographic analyses revealed that the phase transition was accompanied by rotation of the 4-methylphenyl group of the axle component molecule and a simultaneous shift in the position of the PF₆^– counteranion. Crystalline phase transition changes the conformation and position of the DB24C8 molecule relative to the ammonium cation partially; the interaction between the cyclic component and the PF₆^– anion in the crystal changes to a greater extent. Moreover, there are changes in the vibration angle (θ) and birefringence (Δ<i>n</i>) on the (001) face of the crystal transitionally; θ is rotated by +12°, and Δ<i>n</i> is decreased from 0.070 to 0.059 upon heating across the phase transition temperature. The phase transition and accompanying change in the optical properties of the crystal occur reversibly and repeatedly upon heating and cooling processes. The switching rotation of the aromatic plane of the molecule induces a change in the optical anisotropy of the crystal, which is regarded as a demonstration of a new type of optical crystal. Partial replacement of the PF₆^– anion with the bulkier AsF₆^– anion forms crystals with similar crystallographic parameters. An increase in the AsF₆^– content decreases the reversible-phase-transition temperature gradually down to 99 °C (<i>T</i>_end) and 68 °C (<i>T</i>_exo) ([AsF₆^–]:[PF₆^–] = 0.4:0.6)

Thermally-Induced Phase Transition of Pseudorotaxane Crystals: Changes in Conformation and Interaction of the Molecules and Optical Properties of the Crystals

This paper presents a pseudorotaxane that acts as a thermally driven molecular switch in the single-crystal state. Crystals of the cationic pseudorotaxane consisting of dibenzo[24]­crown-8 (DB24C8) and <i>N</i>-(xylylammonium)-methylferrocene as the cyclic and axle component molecules, respectively, undergo crystalline-phase transition at 128 °C with heating and 116 °C with cooling, according to differential-scanning-calorimetry measurements. X-ray crystallographic analyses revealed that the phase transition was accompanied by rotation of the 4-methylphenyl group of the axle component molecule and a simultaneous shift in the position of the PF₆^– counteranion. Crystalline phase transition changes the conformation and position of the DB24C8 molecule relative to the ammonium cation partially; the interaction between the cyclic component and the PF₆^– anion in the crystal changes to a greater extent. Moreover, there are changes in the vibration angle (θ) and birefringence (Δ<i>n</i>) on the (001) face of the crystal transitionally; θ is rotated by +12°, and Δ<i>n</i> is decreased from 0.070 to 0.059 upon heating across the phase transition temperature. The phase transition and accompanying change in the optical properties of the crystal occur reversibly and repeatedly upon heating and cooling processes. The switching rotation of the aromatic plane of the molecule induces a change in the optical anisotropy of the crystal, which is regarded as a demonstration of a new type of optical crystal. Partial replacement of the PF₆^– anion with the bulkier AsF₆^– anion forms crystals with similar crystallographic parameters. An increase in the AsF₆^– content decreases the reversible-phase-transition temperature gradually down to 99 °C (<i>T</i>_end) and 68 °C (<i>T</i>_exo) ([AsF₆^–]:[PF₆^–] = 0.4:0.6)

Thermally-Induced Phase Transition of Pseudorotaxane Crystals: Changes in Conformation and Interaction of the Molecules and Optical Properties of the Crystals

This paper presents a pseudorotaxane that acts as a thermally driven molecular switch in the single-crystal state. Crystals of the cationic pseudorotaxane consisting of dibenzo[24]­crown-8 (DB24C8) and <i>N</i>-(xylylammonium)-methylferrocene as the cyclic and axle component molecules, respectively, undergo crystalline-phase transition at 128 °C with heating and 116 °C with cooling, according to differential-scanning-calorimetry measurements. X-ray crystallographic analyses revealed that the phase transition was accompanied by rotation of the 4-methylphenyl group of the axle component molecule and a simultaneous shift in the position of the PF₆^– counteranion. Crystalline phase transition changes the conformation and position of the DB24C8 molecule relative to the ammonium cation partially; the interaction between the cyclic component and the PF₆^– anion in the crystal changes to a greater extent. Moreover, there are changes in the vibration angle (θ) and birefringence (Δ<i>n</i>) on the (001) face of the crystal transitionally; θ is rotated by +12°, and Δ<i>n</i> is decreased from 0.070 to 0.059 upon heating across the phase transition temperature. The phase transition and accompanying change in the optical properties of the crystal occur reversibly and repeatedly upon heating and cooling processes. The switching rotation of the aromatic plane of the molecule induces a change in the optical anisotropy of the crystal, which is regarded as a demonstration of a new type of optical crystal. Partial replacement of the PF₆^– anion with the bulkier AsF₆^– anion forms crystals with similar crystallographic parameters. An increase in the AsF₆^– content decreases the reversible-phase-transition temperature gradually down to 99 °C (<i>T</i>_end) and 68 °C (<i>T</i>_exo) ([AsF₆^–]:[PF₆^–] = 0.4:0.6)

Francis Hamilton, Leny, [Stirling], to Sir James Edward Smith

Thanks for "Flora Anglica". Making strong progress with "Hortus Malabaricus". Has given commentary on the first volume of the "Herbarium Amboinense" to the Wernerian Society in Edinburgh but doubtful whether it will appear. [William Jackson] Hooker is to compile detailed observations that are suited for neither commentaries and publish them in the Edinburgh Philosophical Journal. Complains that Venlenat, [Augustin Pyramus] de Candolle, [Carl Sigismund] Kunth "and other Goths are overwhelming us with new orders", which he believes [Robert] Brown may be "aiding and abetting", and that they do not understand the difference between an order and a genus as established by Linnaeus