S=1/2 tetracene monoradical cation/anion: ion-based one-dimensional antiferromagnetic chains

The monoradical cation 1(center dot+) and anion 1(center dot-) based on tetracene were generated by one-electron oxidation and one-electron reduction of the bulky tetracene (1), respectively, which contain the largest pi-fused skeletons reported to date. For monoradical species, 1(center dot+) and 1(center dot-), EPR spectra and DFT calculation results indicate the spin density delocalized over the whole molecules. Notably, in the solid state, 1(center dot+) and 1(center dot-), respectively, pack into (1(center dot+))(n) and (1(center dot-)-K-crown)(n), characterized by single-crystal X-ray diffraction studies. The intermolecular interactions of 1(center dot+) and 1(center dot-) are, respectively, through van der Waals forces and exchange couplings supported by metal ions. The monoradical cation polymer (1(center dot+))(n) was the first example based on PAHs. The EPR spectra at 90 K of 1(center dot+) and 1(center dot-) all show forbidden transitions (Delta m(s) = +/- 2), indicating the existence of electronic coupling between the neighboring radicals, with respective 2J = -6.54 K and 2J = -0.22 K characterized by SQUID measurements.

Automated summary

The monoradical cation 1(center dot+) and anion 1(center dot-) based on tetracene were generated by oxidation and reduction, respectively. These species have the largest pi-fused skeletons reported to date. In the solid state, they form crystalline structures with intermolecular interactions supported by van der Waals forces and metal ions. EPR and DFT calculations confirm the delocalization of spin density over the whole molecules.