A Tetrairon Dication Featuring Tetraethynylbenzene Bridging Ligand: A Molecular Prototype of Quantum Dot Cellular Automata

The unprecedented tetrairon dication [{Cp*(dppe)FeC≡C‐}4‐μ‐(1,2,4,5‐C6H2)](PF6)2 (1) was obtained through a sequence of three reactions from 1,2,4,5‐tetraethynylbenzene, Cp*(dppe)FeCl (Cp*=C5Me5, dppe=1,2‐bis(diphenylphosphino)‐ethane), KOtBu, and ferrocenium hexafluorophosphate. The cyclic voltammogram of the target molecule, isolated in 77 % yield, exhibits four well separated and reversible redox events showing that 1 is thermodynamically stable with respect to disproportionation (Kc>106). The tetranuclear dication 1 was characterized by XRD on single crystal, IR and NMR spectroscopies and Mössbauer spectrometry. The experimental data show that 1 behaves as a class II mixed‐valence complex with the positive charges preferentially disposed on antipodal positions. This new molecule can be regarded as a potential molecular prototype of quantum dot cellular automata. A novel tetranuclear iron dicationic complex has been synthesized and isolated as a hexafluorophosphate salt. The dicationic moiety constitutes a structured charge container able to encode binary information in the charge configuration. It constitutes a QCA cell. The IR data are characteristic of a class II mixed‐valence complex, while the physical properties are consistent with a localization of the positive charges on the antipodal positions to minimize coulomb repulsion and favor antiferromagnetic exchange coupling.