担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Communications  

A water-soluble donor–acceptor–donor triad, Dend-MCM, was developed as a ratiometric chemosensor for hydrostatic pressure. In water, the emission intensity from the locally excited state increased, whereas that from the charge-transfer state decreased owing to stronger solvation effects under high-pressure conditions. These findings enable pressure sensing in polar environments.

DOI： 10.1039/d5cc06674c

Web of Science

Scopus

PubMed

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Communications  

Aggregation-induced emission triggered by external stimuli plays an important role in smart materials. Herein, we report the serendipitous discovery that 3Star-Ph-Ph, a soft tripod, forms pressure-induced assemblies with distinctly amplified fluorescence owing to restricted molecular motions within these assemblies.

DOI： 10.1039/d5cc05838d

Web of Science

Scopus

PubMed

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Communications  

Herein, we report the unprecedented discovery of 1 that possesses dynamically tunable chiroptical properties under hydrostatic pressure. Upon hydrostatic pressurization, the g factor inverts from negative to positive. These chiroptical switches are based on pressure-induced conformational change governed by the interplay between macrocyclic flexibility and solvent polarity.

DOI： 10.1039/d5cc05443e

Web of Science

Scopus

PubMed

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Proceedings of the National Academy of Sciences of the United States of America  

Triplet dynamic nuclear polarization (triplet-DNP) is a technique that can obtain high nuclear polarization under moderate conditions. However, in order to obtain practically useful polarization, large single crystals doped with a polarizing agent must be strictly oriented with respect to the magnetic field to sharpen the electron spin resonance (ESR) spectra, which is a fatal problem that prevents its application to truly useful biomolecular targets. Instead of this conventional physical approach of controlling crystal orientation, here, we propose a chemical approach, i.e., molecular design of polarizing agents; pentacene molecules, the most typical triplet-DNP polarizing agent, are modified so as to make the triplet electron distribution wider and more isotropic without loss of the triplet polarization. The thiophene-modified pentacene exhibits a sharper and stronger ESR spectrum than the parent pentacene, and state-of-the-art quantum chemical calculations revealed that the direction of the spin polarization is altered by the modification with thiophene moieties and the size of D and E parameters are reduced from parent pentacene due to the partial delocalization of spin densities on the thiophene moieties. The triplet-DNP with the new polarizing agent successfully exceeds the previous highest ¹H polarization of glassy materials by a factor of 5. This demonstrates the feasibility of a polarizing agent that can surpass pentacene, the best polarizing agent for more than 30 y since triplet-DNP was first reported, in the unoriented state. This work provides a pathway toward practically useful high nuclear polarization of various biomolecules by triplet-DNP.

DOI： 10.1073/pnas.2307926120

Web of Science

Scopus

PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Physical Chemistry Letters  

The photoexcited triplet state of dyes can generate highly polarized electron spins for sensing and dynamic nuclear polarization. However, while triplets exhibit long spin-lattice relaxation times (T1) on the microsecond scale in solids, the polarization quickly relaxes on the nanosecond scale in solution due to the rotational motion of chromophores. Here, we report that the immobilization of dye molecules on a solid surface allows molecular contact with a liquid while maintaining high polarization and long T1 as in a solid. By adsorbing anionic porphyrins on cationic mesoporous silica gel, porphyrin triplets exhibit high polarization and long T1 at the solid-liquid interface of silica and toluene. Furthermore, porphyrin triplets on the solid surface can exchange spin polarization with TEMPO radicals in solution. This simple and versatile method using the solid-liquid interface will open the door for utilizing the photoinduced triplet spin polarization in solution, which has been mainly limited to the solid-state.

DOI： 10.1021/acs.jpclett.3c00627

Web of Science

Scopus

PubMed

記述言語：英語   出版者・発行元：Springer  

Singlet fission (SF), converting a singlet excited state into a spin-correlated triplet-pair state, is an effective way to generate a spin quintet state in organic materials. Although its application to photovoltaics as an exciton multiplier has been extensively studied, the use of its unique spin degree of freedom has been largely unexplored. Here, we demonstrate that the spin polarization of the quintet multiexcitons generated by SF improves the sensitivity of magnetic resonance of water molecules through dynamic nuclear polarization (DNP). We form supramolecular assemblies of a few pentacene chromophores and use SF-born quintet spins to achieve DNP of water-glycerol, the most basic biological matrix, as evidenced by the dependence of nuclear polarization enhancement on magnetic field and microwave power. Our demonstration opens a use of SF as a polarized spin generator in bio-quantum technology.

DOI： 10.1038/s41467-023-36698-4

Web of Science

Scopus

PubMed

CiNii Research

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Physical Chemistry B  

Dynamic electron polarization (DEP), induced by quenching of photoexcited species by stable radicals, can hyperpolarize electron spins in solution at room temperature. Recently, development of technologies based on electron spin polarization such as dynamic nuclear polarization (DNP) has been progressing, where it is important to design molecules that achieve long-lasting DEP in addition to high DEP. Hybridization by linking dyes and radicals is a promising approach for efficient DEP, but strong interactions between neighboring dyes and radicals often result in the rapid decay of DEP. In this study, we introduce a flexible linker into the hybrid system of porphyrin and TEMPO to achieve both efficient DEP and long-lasting DEP. The structural flexibility of the linker switches the interaction between the radical and the triplet, which promotes the DEP process by bringing the radical and the triplet into close proximity, while avoiding abrupt relaxation due to strong interactions. As a result, the new hybridized system exhibits a larger DEP than the unlinked system, while at the same time achieving a DEP lasting more than 10 μs.

DOI： 10.1021/acs.jpcb.2c07936

Web of Science

Scopus

PubMed