Tomohiro Seki

Bio: Tomohiro Seki is an academic researcher from Hokkaido University. The author has contributed to research in topics: Perylene & Isocyanide. The author has an hindex of 29, co-authored 84 publications receiving 3150 citations. Previous affiliations of Tomohiro Seki include Shizuoka University & Max Planck Society.

Design amphiphilic dipolar π-systems for stimuli-responsive luminescent materials using metastable states

Abstract: Some π-conjugated molecules exhibit tunable luminescence—a property that is useful for the next generation of optical devices. Yagai et al. propose a strategy to design these materials on a molecular level, which tailors the emission colour via structural changes in response to mechanical stimuli.

Mechanical stimulation and solid seeding trigger single-crystal-to-single-crystal molecular domino transformations

Abstract: Numerous studies have focused on the mechanical control of solid structures and phase changes in molecular crystals. However, the molecular-level understanding of how macroscopic forces affect the molecules in a solid remains incomplete. Here we report that a small mechanical stimulus or solid seeding can trigger a single-crystal-to-single-crystal transformation from a kinetically isolated polymorph of phenyl(phenyl isocyanide)gold(I) exhibiting blue photoluminescence to a thermodynamically stable polymorph exhibiting yellow emission without the need for heating or solvent. The phase transformation initiates at the location of the mechanical stimulation or seed crystal, extends to adjacent crystals, and can be readily monitored visually by the accompanying photoluminescent colour change from blue to yellow. The transformation was characterized using single crystal X-ray analysis. Our results suggest that the transformation proceeds through self-replication, causing the complex to behave as 'molecular dominoes'.

A Screening Approach for the Discovery of Mechanochromic Gold(I) Isocyanide Complexes with Crystal-to-Crystal Phase Transitions.

Abstract: Mechanoinduced phase transitions of emissive organic crystalline materials have received much attention. Although a variety of such luminescent mechanochromic compounds have been reported, it is challenging to develop mechanochromic compounds with crystal-to-crystal phase transitions in which precise structural information about molecular arrangements can be obtained. Here, we report a screening approach to explore mechanochromic compounds exhibiting a crystal-to-crystal phase transition. We prepared 48 para-substituted (R1) phenyl[para-substituted (R2) phenyl isocyanide]gold(I) complexes designated R1–R2 (six R1 and eight R2 substituents) and then performed three-step screening experiments. The first screening step was selection of emissive complexes under UV light, which gave 37 emissive R1–R2 complexes. The second screening step involved evaluation of the mechanochromic properties by emission spectroscopy. Twenty-eight complexes were found to be mechanochromic. The third screening step involved prepara...

Controlling Mechano‐ and Seeding‐Triggered Single‐Crystal‐to‐Single‐Crystal Phase Transition: Molecular Domino with a Disconnection of Aurophilic Bonds

Abstract: Green and blue polymorphs: A single-crystal-to-single-crystal (SCSC) phase transition of phenyl(3,5-dimethylphenyl isocyanide)gold(I) was triggered by mechanical picking or solid seeding and propagated spontaneously with a domino-like mechanism. As a result, one phase with intense green emission was transformed to another phase with weaker blue emission.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

J-aggregates: from serendipitous discovery to supramolecular engineering of functional dye materials.

Abstract: J-aggregates are of significant interest for organic materials conceived by supramolecular approaches. Their discovery in the 1930s represents one of the most important milestones in dye chemistry as well as the germination of supramolecular chemistry. The intriguing optical properties of J-aggregates (in particular, very narrow red-shifted absorption bands with respect to those of the monomer and their ability to delocalize and migrate excitons) as well as their prospect for applications have motivated scientists to become involved in this field, and numerous contributions have been published. This Review provides an overview on the J-aggregates of a broad variety of dyes (including cyanines, porphyrins, phthalocyanines, and perylene bisimides) created by using supramolecular construction principles, and discusses their optical and photophysical properties as well as their potential applications. Thus, this Review is intended to be of interest to the supramolecular, photochemistry, and materials science communities.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg