The University of Tokyo · Materials Science
Professor Koki Ikemoto's research lab specializes in the design, synthesis, and structural characterization of novel carbon-based nanomaterials and functional molecular architectures. The lab focuses on creating well-defined, discrete molecular systems such as phenylene-based nanocups, nitrogen-doped carbon nanotubes, and aromatic macrocycles, using innovative strategies like geodesic frameworks and single-crystal X-ray crystallography. A key strength lies in combining synthetic precision with in situ structural analysis—particularly through X-ray crystallography in porous coordination networks—to elucidate reaction mechanisms and control molecular reactivity at the atomic level. The ultimate goal is to develop advanced organic materials for optoelectronic applications, including high-efficiency single-layer organic light-emitting devices and selective catalytic transformations.
Figures are computed from collected data and may differ slightly.
A phenylene multiring with a corannulenoidal skeleton was synthesized. Geodesic constraints over 20 phenylene panels resulted in its nanometer-sized, bowl-shaped molecular structure, which was unequivocally revealed by crystallographic analysis. The crystal structure also showed the presence of a bowl-in-bowl dimeric assembly, which was driven by entropic factors in solution.
Pd-mediated aromatic bromination is intriguing to synthetic and organometallic chemists due to both its synthetic utility and, more importantly, a proposed mechanism involving an uncommon Pd(IV)/Pd(II) catalytic cycle. Here, we report an X-ray snapshot observation of a Pd reaction center during a Pd-mediated aromatic bromination in a single crystal of a porous coordination network crystalline scaffold. Upon treatment of a single crystal with N-bromosuccinimide, sequential X-ray snapshots reveale
Nitrogen-doped carbon nanotubes have attracted attention in various fields, but lack of congeners with discrete molecular structures has hampered developments based on in-depth, chemical understandings. In this study, a nanotube molecule doped periodically with multiple nitrogen atoms has been synthesized by combining eight 2,4,6-trisubstituted pyridine units with thirty-two 1,3,5-trisubstituted benzene units. A synthetic strategy involving geodesic phenine frameworks is sufficiently versatile t
In the pore of a porous coordination network, Diels-Alder reactants, a diene and a dienophile, are recognized by donor-acceptor and multiple H-bond interactions, respectively, and fixed at ideal positions for the reaction. Heating the crystals promoted the Diels-Alder reactions with enhanced reactivity and controlled regioselectivity as clearly monitored by in situ X-ray crystallography.
A method for the modular synthesis of aromatic hydrocarbon macrocycles has been developed for base materials in single-layer organic light-emitting devices. The method with Ir-catalyzed direct C-H borylation and Suzuki-Miyaura coupling was concise and scalable, which allowed for a gram-scale preparation of aromatic hydrocarbon macrocycles that have bulky substituents at the periphery. The new arylated hydrocarbon macrocycles enabled a quantitative electro-optical conversion in organic light-emit
Organozinc addition reactions were carried out on an aldehyde within a porous coordination network (see picture) in a single-crystal-to-single-crystal fashion, and the product structure was unambiguously determined by X-ray diffraction. Moreover, a one-pot two-step reaction in a single crystal furnished an ester from an aldehyde without the network losing crystallinity.
A saddle-shaped macromolecule has been synthesized. The molecule was designed as a geodesic saddle with 1,3,5-trisubstituted benzene (named phenine) as the fundamental unit. The phenines were woven into a polygonal framework that was composed of 168 sp<sup>2</sup> -hybridized carbon atoms. The saddle-shaped structure with unique symmetry showed atypical conformational changes. The biaryl linkages in this molecule had a small energy barrier for rotation, and these structural fluctuations resulted
Complexation of C<sub>60</sub> at a conical region of a nanometer-sized geodesic phenylene bowl has been demonstrated. Proton NMR spectroscopy showed formation of a 1:1 complex that was driven by entropy gains for the assembly. Crystallographic analyses revealed its unique ball-in-bowl structure, and the presence of smoothly curved surfaces was unveiled at their interfaces.
"How do we decide the stoichiometry of host-guest complexes?" This question has long been answered by the Job plot since its first report in 1928. However, as the Job plot was claimed to be misleading in 2016, the question became an open question again and called for renewed investigations. An information-theoretic approach, called Akaike's information criterion, is introduced in this study to select the best model of host-guest complexes, which can rank the models with weight of evidence. A few
Abstract The planar trigonal structure of 1,3,5-trisubstituted benzene, named phenine, has been adopted as basic units of polygonal networks to shape nanometer-sized curved organic π-molecules. The phenine design allows for concise syntheses of large carbonaceous molecules reaching 4 kDa by stitching geodesic lines with aryl coupling reactions. In this Account, the development of the defective nanocarbon molecules, i.e., geodesic phenine frameworks, is summarized to overview unique structural/el
Abstract A phenylene multiring with a corannulenoidal skeleton was synthesized. Geodesic constraints over 20 phenylene panels resulted in its nanometer‐sized, bowl‐shaped molecular structure, which was unequivocally revealed by crystallographic analysis. The crystal structure also showed the presence of a bowl‐in‐bowl dimeric assembly, which was driven by entropic factors in solution.
A saddle-shaped nanocarbon molecule was synthesized, which revealed the existence of negative Gauss curvatures on a >3-nm molecular structure possessing 192 π-electrons. The synthesis was facilitated by a protocol developed with Design-of-Experiments optimizations and machine-learning predictions, and spectroscopy and crystallography were used to reveal the saddle-shaped structure of the molecule. Solution-phase analyses showed the presence of dimeric assembly, and crystallographic analyses reve
[n]Cyclo-para-phenylene congeners of n = 12, 16, 20 with n/2 nitrogen atoms were synthesized via Pt-mediated one-pot macrocyclization reactions. The reaction allowed diversification of participatin...
A concise method for the synthesis of [n]cyclo-1,3-pyrenylenes has been developed. A Ni-mediated macrocyclization was found effective for the one-pot macrocyclization of the corresponding dibromide...
A method for the synthesis of metal-doped aromatic macrocycles has been developed. The method, i.e., metal-templated oligomeric macrocyclization via coupling, adopts Ni as the template and assembles five pyridine units via a Ni-mediated coupling reaction to form aryl-aryl linkages. A pentameric oligopyridyl macrocycle was selectively obtained in good yield, and the reaction was also applicable to a gram-scale synthesis. The pentameric oligopyridyl macrocycle captured d<sup>8</sup>-Ni(II) at the
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