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

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.