Geometrical Evolution and Formation of the Photoproduct in the Cycloreversion Reaction of a Diarylethene Derivative Probed by Vibrational Spectroscopy

The geometrical evolution of the reactant and formation of the photoproduct in the cycloreversion reaction of a diarylethene derivative were probed using time-resolved absorption spectroscopies in the visible to near-infrared and mid-infrared regions. The time-domain vibrational data in the visible region show that the initially formed Franck-Condon state is geometrically relaxed into the minimum in the excited state potential energy surface, concomitantly with the low-frequency coherent vibrations. Theoretical calculations indicate that the nuclear displacement in this coherent vibration is nearly parallel to that in the geometrical relaxation. Time-resolved mid-infrared spectroscopy directly detected the formation of the open-ring isomer with the same time constant as the decrease of the closed-ring isomer in the excited state minimum. This observation reveals that no detectable intermediate, in which the population is accumulated, is present between the excited closed-ring isomer and the open-ring isomer in the ground state.     

Thiazolidinediones with thyroid hormone receptor agonistic activity.

Several thiazolidinedione derivatives (3-7) were designed and synthesized as candidate thyromimetic drugs. Among them, the dihydrogenated compounds, such as 5-2-[[4-(3-tert-butyl-4-hydroxyphenyl)oxy-3,5-diiodophenyl] ethyl]-2,4-thiazolidinedione (6b) and its 3-isopropyl analog (7b), exhibited potent thyroid hormone receptor alpha 1 (TR alpha 1) activation activity.     

A Kinetically Stabilized Nitrogen-Doped Triangulene Cation: Stable and NIR Fluorescent Diradical Cation with Triplet Ground State

A kinetically-stabilized nitrogen-doped triangulene cation derivative has been synthesized and isolated as the stable diradical with a triplet ground state that exhibits near-infrared emission. As was the case for a triangulene derivative we previously synthesized, the triplet ground state with a large singlet-triplet energy gap was experimentally confirmed by magnetic measurements. In contrast to the triangulene derivative, the nitrogen-doped triangulene cation derivative is highly stable even in solution under air and exhibits near-infrared absorption and emission because the alternancy symmetry of triangulene is broken by the nitrogen cation. Breaking the alternancy symmetry of triplet alternant hydrocarbon diradicals by a nitrogen cation would therefore be an effective strategy to create stable diradicals possessing magnetic properties similar to the parent hydrocarbons but with different electrochemical and photophysical properties.     

Object Transportation System Mimicking the Cilia of Paramecium aurelia Making Use of the Light‐Controllable Crystal Bending Behavior of a Photochromic Diarylethene

The design of an object transportation system exploiting the bending behavior of surface‐assembled diarylethene crystals is reported. A photoactuated smart surface based on this system can transport polystyrene beads to a desired area depending on the direction of the incident light. Two main challenges were addressed to accomplish directional motion along a surface: first, the preparation of crystals whose bending behavior depends on the direction of incident light; second, the preparation of a film on which these photochromic crystal plates are aligned. Nuclei generation and nuclear growth engineering were achieved by using a roughness‐controlled dotted microstructured substrate. This system demonstrates how to achieve a mechanical function as shown by remote‐controlled motion along a surface.     

3-D measurement of 2-D jet by 3-D 3-C SPIV

Journal of Visualization - The stereo PIV, commonly known as the SPIV, is capable of measuring all the three velocity components in a two-dimensional measurement plane and thus classified as 2-D...     

Fluorescent supramolecular polymers of barbiturate dyes with thiophene-cored twisted π-systems

Because supramolecular polymerization of emissive π-conjugated molecules depends strongly on π–π stacking interaction, the formation of well-defined one-dimensional nanostructures often results in a decrease or only a small increase of emission efficiency. This is also true for our barbiturate-based supramolecular polymers wherein hydrogen-bonded rosettes of barbiturates stack quasi-one-dimensionally through π–π stacking interaction. Herein we report supramolecular polymerization-induced emission of two regioisomeric 2,3-diphenylthiophene derivatives functionalized with barbituric acid and tri(dodecyloxy)benzyl wedge units. In CHCl₃, both compounds are molecularly dissolved and accordingly poorly emissive due to a torsion-induced non-radiative decay. In methylcyclohexane-rich conditions, these barbiturates self-assemble to form crystalline nanofibers and exhibit strongly enhanced emission through supramolecular polymerization driven by hydrogen-bonding. Our structural analysis suggests that the barbiturates form a tape-like hydrogen-bonding motif, which is rationalized by considering that the twisted geometries of 2,3-diphenylthiophene cores prevend the competing rosettes from stacking into columnar supramolecular polymers. We also found that a small difference in the molecular polarity originating from the substitutional position of the thiophene core influences interchain association of the supramolecular polymers, affording different luminescent soft materials, gel and nanosheet.

Two barbiturate dyes with regioisomeric thiophene-cored twisted π-systems show strongly enhanced emission through supramolecular polymerization. The supramolecular polymers thus formed exhibit distinct emission colors and degree of agglomeration.     

1,2,3-Tri(9-anthryl)benzene: Photophysical Properties and Solid-State Intermolecular Interactions of Radially Arranged,Congested Aromatic π-Planes**

We report the Negishi coupling based synthesis of 1,2,3-tri(9-anthryl)benzene derivatives containing three radially arranged anthracenes in a π-cluster. In the crystalline state of the unsubstituted derivative, intermolecular π–π and CH–π interactions between the anthracene units drive the formation of the two-dimensional packing structure. Owing to though-space π-conjugation between anthracene units, the substances have unique electronic properties. The excited-state dynamic behavior occurring between the three anthracene moieties, such as exciton localization/delocalization, was elucidated by means of transient absorption measurements and quantum chemical calculations. Interestingly, even though the three anthracenes are closely oriented with approximately 3.0 Å between their C-9 positions, exciton localization on two anthracene units is energetically favorable because of the flexible nature of the radially arranged aromatic rings.     

Molecular crystalline capsules that release their contents by light

Here, we present single crystalline capsules of a photoresponsive molecule produced by simple recrystallization from organic solutions without direct human processing. During the crystal growth process, a movie was taken of the capsule taking in the organic solution. The capsules responded rapidly (<1 s) to the UV light stimuli and released the captured solution or solute. In principle, they can take in any substance dissolved in organic solvents, and their size can be controlled. Moreover, the capsule can be broken by multi-photon excitation using a near-infrared laser within the biological window. Furthermore, because the molecular packing in the crystal is unidirectional, the response can be controlled by the polarization of the light. This study shows the new potential of photoresponsive molecules.

A novel diarylethene formed “crystalline capsules” containing liquid inclusions, and chemicals trapped in the capsules were released by photoinduced breaking. Operations by multiphoton and linear polarized light were demonstrated.