Experimental and Theoretical Characterization of 4π-Electron Möbius Aromatic System of a 1,2-Digermacyclobutadiene†

Tomohiro Sugahara; Daisuke Hashizume; Arturo Espinosa Ferao; Koichiro Masada; Norihiro Tokitoh; Takahiro Sasamori

doi:10.1002/anie.202413426

Experimental and Theoretical Characterization of 4π-Electron Möbius Aromatic System of a 1,2-Digermacyclobutadiene^†

Angew Chem Int Ed Engl. 2025 Jan 2;64(1):e202413426. doi: 10.1002/anie.202413426. Epub 2024 Oct 28.

Authors

Tomohiro Sugahara¹, Daisuke Hashizume², Arturo Espinosa Ferao³, Koichiro Masada⁴, Norihiro Tokitoh¹, Takahiro Sasamori⁴

Affiliations

¹ Institute for Chemical Research, Kyoto University Gokasho, Uji, Kyoto, 611-0011, Japan.
² RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
³ Departamento de Química Orgánica, Facultad de Química, Universidad de Murcia Campus de Espinardo, 30100, Murcia, Spain.
⁴ Division of Chemistry, Institute of Pure and Applied Sciences, and Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8571, Japan.

PMID: 39235154
DOI: 10.1002/anie.202413426

Abstract

We present the visualization of the experimental valence electron-density distribution (EDD) in the isolated 1,2-digermacyclobutadiene ring system, revealing the unique 4π electron-delocalization on the four-membered Ge₂C₂ ring. A remarkably high Möbius 4π-electron aromatic character in the Ge₂C₂ ring can be suggested from theoretical calculations, in sharp contrast to the significant antiaromaticity of the all-carbon cyclobutadiene ring.

Keywords: 1,2-Digermacyclobutadiene; Aromaticity; Heavier-Main-Group Elements; NICS; Valence-Electron-Density-Distribution Analysis.

Abstract

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