A multifunctional pseudo-[6]oxocarbon molecule innate to six accessible oxidation states

Summary

Multi-electron redox behavior is common for inorganic compounds but exceptionally rare for organic molecules. Herein, the synthesis and full characterization of a simple organic molecule carrying the formula benzo[1,2-c:3,4-c′:5,6-c″]tris([1,2,5]thiadiazole) 2,2,5,5,8,8-hexaoxide, abbreviated as tripak, are presented. Tripak constitutes a derivative of the thermodynamically unstable [6]oxocarbon C₆O₆, where all C=O groups are transformed into three dioxothiadiazole units, leaving a C₆ ring in the center. The electron-withdrawing dioxothiadiazoles allow for a peerless uptake of six electrons by tripak in five consecutive reduction steps, and five of the six possible valence forms were fully investigated. Remarkably, the number of stored electrons elicits different types of aromaticity, ranging from non-aromatic to Hückel to Baird, and multifunctionality. Tripak⁰ features strong anion-π binding of halides. Tripak¹⁻ and tripak³⁻ represent radicals, and the former is innate to qubit properties. Tripak²⁻ is a blue dye with red fluorescence, and tripak⁴⁻ emerges as a diradicaloid with a nearly zero singlet-triplet gap.