The University of Osaka · Materials Science
Professor Norimitsu Tohnai's research lab specializes in supramolecular chemistry and solid-state photophysics, focusing on the design and control of molecular assemblies that exhibit tunable fluorescence properties. The lab explores how precise molecular arrangements—particularly π-stacked anthracene derivatives and hydrogen-bonded networks—govern excited-state behavior and luminescence in the solid state. By leveraging molecular recognition, crystal engineering, and stimuli-responsive frameworks, the lab develops functional materials with applications in optical sensing, smart materials, and luminescent devices. Key innovations include solvent-dependent fluorescence color tuning, water-responsive structural transformations, and rigid supramolecular architectures for fluorescence enhancement.
Figures are computed from collected data and may differ slightly.
The construction and precise control of the face-to-face π-stacked arrangements of anthracene fluorophores in the crystalline state led to a remarkable red shift in the fluorescence spectrum due to unprecedented excited oligomer formation. The arrangements were regulated by using organic salts including anthracene-1,5-disulfonic acid (1,5-ADS) and a variety of aliphatic amines. Because of the smaller number of hydrogen atoms at the edge positions and the steric effect of the sulfonate groups, 1,
A dramatic change of solid-state fluorescence properties triggered by molecular arrangements of anthracene moieties was obtained by using organic salts of ADS with primary amines, indicating that modification of the amines enables us to tune the properties.
Solid-state fluorescence enhancement was achieved by preparation of rigid packing that was afforded by disposition of benzylamine into tubulate spaces, serving as a powerful and useful strategy for the enhancement.
Luminescent jewels: Unusually shaped fluorescent supramolecular clusters assemble into one-dimensional π-stacked supramolecular beads to eventually crystallize with a wide range of solvent molecules (see picture). The included solvent molecules modulate the fluorescence colors of the inclusion crystals from blue to orange-yellow as is known for the colors of gemstones. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed,
Just add water: A cube-like hydrogen-bonding network in a fluorescent supramolecular cluster dynamically deforms upon the specific addition of a water molecule. The deformation is amplified through the conformational change of the cluster to result in the transformation of host frameworks. This transformation provides water-responsive guest-exclusion and fluorescent-modulation behaviors.
The supramolecular chirality of 1D ladder-type hydrogen-bond networks composed of primary ammonium carboxylates was determined based on topological considerations. Chirality in such networks is based on the absolute configuration of the primary ammonium cation, which arises from discrimination between the two oxygen atoms of the carboxylate anion. The configurations of the cations and anions generate topological diversity in the networks, which are classified into six subgroups. In the Cambridge
Potential nanoparticle precursors: Triphenylmethylamine (TritylNH2) and various sulfonic acids (RSO3H; R=phenyl in the space-filling representation) assemble into [4+4] ion-pair clusters in the solid state and in solution. The shapes and sizes of these clusters are controlled by the sulfonic acid substituents. Fabrication of the clusters is convenient and efficient, and this method may be used to synthesize organic nanoparticles. Supporting information for this article is available on the WWW un
A crystalline hydrogen-bonded framework with permanent porosity, built by rod-like struts and engineered to bear ultra-fast molecular rotors between two triple bonds, offers the possibility of controlling the rotational rates upon CO<sub>2</sub> adsorption. CO<sub>2</sub> enters the pores from the gas phase and reduces the rotational rates from the extremely fast regime of 10<sup>7</sup> Hz at 216 K to 10<sup>5</sup> Hz. The CO<sub>2</sub>-rotor interaction was evident from the <sup>2</sup>H NMR
Porous organic salts (POSs) are porous organic materials, in which various aromatic sulfonic acids and amines are regularly self-assembled by charge-assisted hydrogen bonding. POSs exhibit high solubility in highly polar solvents. Therefore, they are prepared via facile recrystallization and exhibit high recyclability. In this study, tetrahedral-structured tetrasulfonic acid and triphenylmethylamine (TPMA) were combined to construct POSs with rigid diamond networks called diamondoid porous organ
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