Nobuhiro Yanai

We show that structural changes of a guest molecule can trigger structural transformations of a crystalline host framework. Azobenzene was introduced into a flexible porous coordination polymer (PCP), and cis/trans isomerizations of the guest azobenzene by light or heat successfully induced structural transformations of the host PCP in a reversible fashion. This guest-to-host structural transmission resulted in drastic changes in the gas adsorption property of the host-guest composite, displayin

Photon upconversion based on triplet-triplet annihilation (TTA-UC) has attracted much interest because of its possible applications to renewable energy production and biological fields. In particular, the UC of near-infrared (NIR) light to visible (vis) light is imperative to overcome the Shockley-Queisser limit of single-junction photovoltaic cells, and the efficiency of photocatalytic hydrogen production from water can also be improved with the aid of vis-to-ultraviolet (UV) UC. However, both

A cyanide-bridged bimetallic ferromagnet, [Ni(dipn)]2[Ni(dipn)(H2O)][Fe(CN)6]2·11H2O (dipn = N,N-di(3-aminopropyl)amine) providing a 3-D microporous framework, shows reversible ferromagnet/paramagnet conversion associated with a gaseous water-induced crystal-to-amorphous-like phase transformation

Monodisperse polyhedral metal-organic framework (MOF) particles up to 5 μm in size, large enough to enable in situ optical imaging of particle orientation, were synthesized by the strategy of simultaneous addition of two capping ligands with different binding strength during crystallization. Upon dispersing them in ethylene glycol and applying AC electric field, the particles facets link to form linear chains. We observe well-regulated crystal orientation not only for rhombic dodecahedra all of

A redox sandwich: Oxidative and intercalative polymerization of pyrrole was conducted within the nanoslits of a layered open coordination framework containing redox-active sites. The resulting polypyrrole, which can be isolated from the host framework, exists as stacked sheet polymer objects, the orientation and morphology of which are directly related to those of the original coordination-polymer template. Detailed facts of importance to specialist readers are published as ”Supporting Informati

MOFs get attraction: Supraparticle self-assembly of a colloidal metal–organic framework (MOF) is achieved through simple capillary and van der Waals attractions. When suspensions of MOF particles are allowed to evaporate, hexagonal packings with controlled crystal orientation result (see scheme). The self-assembly can be visualized at the single-particle level. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not

Ultraviolet (UV, λ<400 nm) light is essential for various photochemical reactions, but its intensity in the solar spectrum is very low, and light sources that artificially generate high-energy UV light are inefficient and environmentally unfriendly. A solution to this problem is photon upconversion (UC) from visible (vis, λ>400 nm) light to UV light. Among several mechanisms, UC based on triplet-triplet annihilation (TTA-UC) in particular has made remarkable progress in recent years. The develop

Aggregation-induced photon upconversion (iPUC) based on control of the triplet energy landscape is demonstrated for the first time. When a triplet state of a cyano-substituted 1,4-distyrylbenzene derivative is sensitized in solution, no upconverted emission based on triplet-triplet annihilation (TTA) was observed. In stark contrast, crystalline solids obtained by drying the solution revealed clear upconverted emission. Theoretical studies unveiled an underlying switching mechanism: the excited t

Several energy-demanding photoreactions require harsh UV light from inefficient light sources. The conversion of low-energy visible light to high-energy singlet states via triplet-triplet annihilation upconversion (TTA-UC) could offer a solution for driving such reactions under mild conditions. We present the first annihilator with an emission maximum in the UVB region that, combined with an organic sensitizer, is suitable for blue-to-UVB upconversion. The annihilator singlet was successfully em

It is pivotal to achieve efficient triplet-triplet annihilation based photon upconversion (TTA-UC) in the solid-state for enhancing potentials of renewable energy production devices. However, the UC efficiency of solid materials is largely limited by low fluorescence quantum yields that originate from the aggregation of TTA-UC chromophores and also by severe back energy transfer from the acceptor singlet state to the singlet state of the triplet donor in the condensed state. In this work, to ove

Conversion of near-infrared photons to visible light in rubrene based systems is made 20x more efficient when mixed with 0.5% wt DBP. This is not because singlet fission in rubrene is supressed, but because of reduced triplet losses.

Upconverting near-infrared (NIR) light (λ > 700 nm) to violet light (λ < 450 nm) based on triplet-triplet annihilation (TTA) is achieved for the first time by developing a silyl-substituted anthracene violet emitter and its sensitization by an osmium complex showing a singlet-to-triplet (S-T) absorption in the NIR range.