Ken-ichi Yamashita

Lanthanum β-Tetracyanoporphyrin Double-Decker Complexes: Four-Electron Reduction and Slow Ligand Rotation Porphyrin double-decker complexes undergo multiple redox processes that significantly alter their structural and electronic properties, although most studies have focused on oxidation processes. Studi...

Lanthanum β-Tetracyanoporphyrin Double-Decker Complexes: Four-Electron Reduction and Slow Ligand Rotation | ChemRxiv - doi.org/10.26434/che...

Synthesis and Characterization of (R)‐ and (S)‐1,1′‐Bi‐2‐Naphtholato Coordinated Gallium(III) Porphyrins and Their Chiroptical Properties Gallium porphyrins bearing chiral bi-2-naphtholato ligands are synthesized and characterized. Single-crystal X-ray diffraction and various spectroscopic analyses confirmed their structures. Circular ...

Excited to share our new paper in Eur. J. Inorg. Chem.! 🎉
Proud to collaborate with an amazing international team on this research!

chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/... （Open Access）

Cover Feature: Effect of Chalcogen Interaction on the Structure of Methine‐Bridged Trichalcogenophenes The Cover Feature illustrates the stabilizing chalcogen interactions between sulfur atoms in ZZ-methine-bridged trithiophene by using the metaphor of a chamber ensemble. The intramolecular S···S chal...

Thrilled to announce our trichalcogenophene research is the Cover Feature of #ChemEurJ! The beautiful cover by Rio's cousin uses a chamber ensemble metaphor to illustrate the harmonious S···S chalcogen interactions that stabilize our ZZ-trithiophene.
doi.org/10.1002/chem...

We've already discovered fascinating photoluminescence behaviors and unique isomerization dynamics, plus synthesized larger molecular architectures. These insights enable designing materials with controlled stereochemistry and enhanced properties. Excited to share more soon!

Personally, I'm most excited about successfully reproducing the solution-phase geometric isomer ratios using GOAT conformer search (recently introduced in ORCA 6.0) combined with CENSO. This problem had puzzled us for a long time, and solving it significantly expanded our computational toolkit.

Trichalcogenophenes have three geometric isomers, but trithiophene and trifuran show dramatically different stability patterns. We discovered this stems from intramolecular S···S interactions between adjacent thiophene rings using interaction analysis (NCI, AIM, etc.) mastered for this study.

Effect of Chalcogen Interaction on the Structure of Methine‐Bridged Trichalcogenophenes The stereochemistry of methine-bridged trichalcogenophenes was elucidated through comprehensive structural analyses. Trithiophene showed a strong preference for the ZZ configuration, whereas its trif...

Delighted to announce our new research published in #ChemEurJ —selected as a Hot Paper!
This marks an important milestone as my first publication outside porphyrinoid chemistry. Together with Rio (PhD student), we've pioneered new insights into methine-bridged poly/oligothiophenes.
(Open Access)

Honored this work appears in AsianJOC's Special Collection for Prof. Masahiko Iyoda. We shared Tokyo Metropolitan University - I was an assistant prof. while he was a professor in a different lab in the same department. We're also alumni of the same high school, though from different generations! 🎓✨

We found that steric bulk of meso-substituents determines their tilt angle relative to the isophlorin macrocycle, critically controlling antiaromaticity strength. Bulkier substituents preserve stronger antiaromaticity!
Computational evaluation was achieved with Haruna's collaboration 👥

Tuning Antiaromaticity Through Meso‐Substituent Orientation in Core‐Modified Isophlorins The antiaromaticity of dithiadioxaisophlorins is controlled by the steric bulkiness of meso-substituents through their tilt angle relative to the macrocycle. Bulkier substituents maintain larger angl....

When Maika synthesized thienyl-substituted isophlorins for another purpose, she noticed they showed weaker antiaromaticity than others. This sparked our investigation into the relationship between substituents and antiaromaticity using both synthesis and computation.
DOI: 10.1002/ajoc.202500372 (OA)

Our Name and Logo

Starting today, my affiliation's English name changed:
Osaka University → The University of Osaka
(Japanese name remains unchanged:　大阪大学)
www.osaka-u.ac.jp/en/guide/Our...

Effect of Chalcogen Interaction on the Structure of Methine-Bridged Trichalcogenophenes

Authors: Rio Nishimura, Ken-ichi Yamashita
DOI: 10.26434/chemrxiv-2025-2s0pv

Tuning Antiaromaticity through meso-Substituent Orientation in Core-Modified Isophlorins

Authors: Maika Isoda, Haruna Sugimura, Yusuke Honda, Ken-ichi Yamashita
DOI: 10.26434/chemrxiv-2025-nrvzb

The package claims "Japanese home style noodles" but interestingly, this cheese yakisoba isn't sold in Japan. While Maruchan is indeed a major instant noodle brand, cheese-topped yakisoba isn't something you'd typically find in Japan. I'm quite curious about how it actually tastes!

Front Cover: 20π Antiaromatic Isophlorins without Metallation or Core Modification (Eur. J. Org. Chem. 46/2022) The Front Cover shows a calligraphy drawing of the structure of the antiaromatic isophlorin synthesized for the first time with this study. Peripheral substituents and negative charge are omitted for....

2/2 The free base that led to our latest complex. The work made the Cover: hand-drawn using traditional Japanese calligraphy! The side texts in archaic Hiragana are so old-style that even most Japanese readers find them challenging to read!

See paper link in cover page: doi.org/10.1002/ejoc...

Facile Redox‐Induced Aromatic–Antiaromatic Interconversion of a β‐Tetracyano‐21,23‐Dithiaporphyrin under Ambient Conditions Facile redox-induced aromatic–antiaromatic interconversion was accomplished with β-tetracyano-21,23-dithiaporphyrin. The introduced cyano groups not only increased the reduction potentials of the por....

1/2 The origin story! This was my first paper on antiaromatic compounds, where we designed and synthesized the original antiaromatic system. A key milestone that led to our recent discoveries.

doi.org/10.1002/chem...

Synthesis and Characterization of an Air‐Stable Tin(IV) β‐Tetracyanoisophlorin Complex: Enhanced Antiaromaticity through Metal Complexation. The synthesis and characterization of a novel air-stable Sn(IV) β-tetracyanoisophlorin complex is described. The complex was obtained by reducing the corresponding Sn(IV) β-tetracyanoporphyrin with h...

Exciting new paper on an antiaromatic β-tetracyanoisophlorin! The Sn(IV) complex exhibits enhanced antiaromaticity compared to free base. Crystal structure revealed a surprising dianionic complex with axial anions, not the expected neutral complex.

doi.org/10.1002/ajoc... (Open Access)

Efficient Synthesis of Arylenedioxy‐Bridged Porphyrin Dimers through Catalyst‐Free Nucleophilic Aromatic Substitution Rigid bridges: A series of porphyrin dimers bridged by one or two arylenedioxy linkers was successfully synthesized in high yields by catalyst-free nucleophilic aromatic substitution. The orientation...

This unusual guest binding stems from the host's rigidity. We discussed the synthesis and structure in our earlier paper (doi.org/10.1002/cplu...) - where we also put special emphasis on developing the synthetic methodology.

Outstanding Enhancement in the Axial Coordination Ability of the Highly Rigid Cofacial Cyclic Metalloporphyrin Dimer The unusual axial coordination on CuII and NiII ions in the cofacial cyclic porphyrin dimer was induced by its remarkably high structural rigidity without the assistance of electron-withdrawing subst...

Sharing our previous work on metalloporphyrin hosts! While Zn porphyrins are conventionally chosen for axial coordination, we demonstrated successful binding with Ni and Cu porphyrins - metals typically known for their weak axial coordination ability.
doi.org/10.1002/ajoc...

Surprised by the sudden follower growth - found out I'm in the Supramol Chem starter kit! Grateful and amazed to see so many supramolecular chemists here on Bluesky.

Front Cover: Stable Antiaromatic [16]Triphyrin(2.1.1) with Core Modification: Synthesis Using a 16π Electrocyclic Reaction (Chem. Eur. J. 69/2024) The Front Cover shows trioxa[16]triphyrin(2.1.1), a novel 16π antiaromatic contracted porphyrinoid that has been synthesized and characterized. The synthesis involves the oxidation of dihydrotrioxatr...

Thrilled to share that our recent paper on antiaromatic triphyrin synthesis was selected as the Front Cover of Chemistry - A European Journal! Check out our art featuring the key 16π electrocyclization.
chemistry-europe.onlinelibrary.wiley.com/doi/full/10....

We've discovered other similar cyclization reactions and look forward to reporting them soon! During mechanism studies, this was my first experience using xtb/CREST/CENSO for conformational searching. Currently using this approach extensively with results coming soon!

Stable Antiaromatic [16]Triphyrin(2.1.1) with Core Modification: Synthesis Using a 16π Electrocyclic Reaction The first stable antiaromatic trioxa[16]triphyrin(2.1.1) was synthesized and characterized using a core modification strategy. The synthesis involves a key intermediate, dihydrotrioxatriphyrin(2.1.1)...

Hello Bluesky! Excited to share that one of my research interests is antiaromaticity. We recently published our work on the synthesis of antiaromatic triphyrin via a serendipitously discovered 16π electrocyclization.
doi.org/10.1002/chem... (Open Access)