S = 1/2 tetracene monoradical cation/anion: ion-based one-dimensional antiferromagnetic chains†
Abstract
The monoradical cation 1˙+ and anion 1˙− based on tetracene were generated by one-electron oxidation and one-electron reduction of the bulky tetracene (1), respectively, which contain the largest π-fused skeletons reported to date. For monoradical species, 1˙+ and 1˙−, EPR spectra and DFT calculation results indicate the spin density delocalized over the whole molecules. Notably, in the solid state, 1˙+ and 1˙−, respectively, pack into (1˙+)n and (1˙−-K-crown)n, characterized by single-crystal X-ray diffraction studies. The intermolecular interactions of 1˙+ and 1˙− are, respectively, through van der Waals forces and exchange couplings supported by metal ions. The monoradical cation polymer (1˙+)n was the first example based on PAHs. The EPR spectra at 90 K of 1˙+ and 1˙− all show forbidden transitions (Δms = ±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.
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