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：Nature Communications  

Polarized electron spins in photoexcited triplet states enable dynamic nuclear polarization (DNP) to enhance magnetic resonance imaging (MRI) sensitivity. For a practical nuclear polarization of 10%, single crystals must be precisely oriented in a magnetic field to generate narrow electron spin resonance lines, which is not appropriate for actual medical applications. Here, substituted fullerenes as triplet polarizing agents enable ¹H polarizations above 10%, even for random molecular orientations. While they have not been used as polarizing agents for triplet-DNP because of electron spin relaxation via pseudo-rotation, we overcome this by chemical modification of two sites on C<inf>60</inf> fullerenes. Symmetry considerations reveal fullerenes that avoided pseudo-rotations. Di-substituted fullerenes are ideal polarizing agents with sharp linewidths and long relaxation times that enabled 14.2% ¹H polarization in randomly oriented orientations. Optimized polarizing agents represent a promising approach for ultra-sensitive MRI medical diagnostics without the need for DNP under cryogenic temperatures and severe orientation control.

DOI： 10.1038/s41467-025-66211-y

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：Journal of the American Chemical Society  

Light-driven spin hyperpolarization of organic molecules is a crucial technique for spin-based applications such as quantum information science (QIS) and dynamic nuclear polarization (DNP). Synthetic chemistry provides the design of spins with atomic precision and enables the scale-up of individual spins to hierarchical structures. The high designability and extended pore structure of metal-organic frameworks (MOFs) can control interactions between spins and guest molecules. However, the effective design of polarizing radical electron spins by photoexcitation in MOFs has been unexplored. Here, we show that it is possible to effectively hyperpolarize radical electron spins by harvesting mobile excitons in MOFs. As a proof of concept, we introduce 4-carboxy TEMPO molecules as electron spins into MOF-525, which contains an array of porphyrin chromophores, and demonstrate that this light-harvesting MOF system generates a spin-polarized excited quartet state and doublet ground state even by doping a small amount of electron spins. The current material design leads to the creation of highly spin-polarized nanospaces that can be used for quantum sensing and DNP by efficiently generating high-spin polarization in MOFs doped with small amounts of electron spins to prevent spin relaxation.

DOI： 10.1021/jacs.4c14916

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 Science  

Dynamic nuclear polarization (DNP) significantly improves the sensitivity of magnetic resonance imaging, and its most important medical application is cancer diagnosis via hyperpolarized ¹³C-labeled pyruvate. Unlike cryogenic DNP, triplet-DNP uses photoexcited triplet electrons under mild conditions. However, triplet-DNP of pyruvate has not been observed because of incompatibility of the hydrophobic polarizing agent with hydrophilic pyruvate. This work demonstrates that supramolecular complexation with β-cyclodextrin can disperse 4,4′-(pentacene-6,13-diyl)dibenzoate (NaPDBA), a pentacene derivative with hydrophilic substituents, even in the presence of high sodium pyruvate concentrations. The polarization of photoexcited triplet electron spins in NaPDBA was transferred to the ¹³C spins of sodium pyruvate via triplet-DNP of ¹H spins in water and ¹H-to-¹³C cross-polarization. This provides an important step toward the widespread use of ultra-sensitive MRI for cancer diagnosis.

DOI： 10.1039/d3sc04123a

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：Chemical Science  

Anion-responsive dipyrrolyldiketone and phenalenyl units covalently linked by a spiroboronium unit form π-electronic cations with orthogonally arranged π-systems. Conformations of the anion-binding unit are dependent on the coexisting counteranions in the solution and solid states. Orthogonally arranged π-electronic cations afford solid-state ion-pairing assemblies via double ⁱπ–ⁱπ interactions at the dipyrrolyldiketone anion complex and the phenalenyl units. Transient absorption spectra revealed electron transfer from anion-binding π-units to orthogonally arranged π-electronic cations, which could be modulated by the coexisting counteranions. Orthogonally arranged π-electronic cations exhibit pressure-responsive photophysical properties.

DOI： 10.1039/d6sc05424b

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：Chemistry A European Journal  

Artificial chemosensors have evolved from simple host–guest systems to sophisticated functional platforms for bioanalysis, chiral discrimination, diagnostics, and imaging. However, their sensitivity remains limited when the signal output directly follows intrinsic binding equilibria. One promising strategy for overcoming this constraint is the integration of allosteric signal amplification and molecular recognition. In this review, we provide an overview of the recent advances in polymer chemosensors that operate through supramolecular allosteric signal-amplification sensing (SASS), in which an initial recognition event is propagated through a polymer framework to amplify output signals. Representative examples of homotropic and heterotropic allosteric systems are discussed, highlighting how polymer-mediated conformational or aggregation changes enhance sensitivity toward challenging analytes such as anions, amino acids, saccharides, and other biologically relevant molecules. We also highlight the emerging concept of a dynamic allosteric effector, in which the effector itself is no longer fixed but rather continuously tunable through supramolecular polymerization. This new design principle links assembly state, molecular recognition, and signal amplification within a single adaptive framework. Collectively, these advances establish polymer-based allosteric systems as a versatile foundation for next-generation ultrahigh-sensitivity chemosensors and adaptive supramolecular materials.

DOI： 10.1002/chem.71624

Web of Science

Scopus

PubMed

This book explores hydrostatic pressure chemistry and its applications in smart/functional molecular, supramolecular, and biological systems. Hydrostatic pressure is a fundamental and widespread stimulus that uniquely influences various biological, chemical, and physical phenomena. Recently, the scientific community has shown considerable interest in controlling reactions and rates through hydrostatic pressure. This volume provides a comprehensive historical overview of hydrostatic pressure studies, from early research topics to contemporary mechanochemistry and mechanobiology. It is aimed at both theoretical and experimental chemists specializing in supramolecular and (bio)macromolecular chemistry, mechanoscience, material science, and engineering. Readers will gain a thorough understanding of the longstanding mysteries within mechanoscience and related fields.

DOI： 10.1007/978-981-95-7461-2

Scopus

担当区分：筆頭著者   記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）   出版者・発行元：光化学協会  

<p>Hydrostatic pressure, an isotropic mechanical stimulus, directly modulates molecular volume relating to solvation and so on, thereby enabling precise control of ground and excited state structures and reactivity. This review highlights recent advances in pressure-mediated photochemistry, with particular focus on mechanistic connections between thermodynamics and optical properties/functions. As a representative example, recent studies have demonstrated that the chiroptical properties can be modulated by hydrostatic pressure, through the cooperative effects of solvent environment and molecular flexibility. Fluorescence-based pressure chemosensors are also presented, including surface-immobilized probes and ratiometric sensors developed through the polymer design. Furthermore, pressure modulation of photoreactions is examined, covering reversible photochromism, pressure-induced intramolecular photocyclodimerization, and the control of singlet fission kinetics. Molecular design guidelines that integrate conformational flexibility with controlled solvation are important for enhancing pressure sensitivity, to enable the development of pressure-responsive chromophores for incorporating into mechanoresponsive devices and biological sensors.</p>

DOI： 10.60391/koukagaku.56.3_150

CiNii Research