Magnetic Multistability in an Anion‐Radical Pimer

Stable Crystalline Nanohoop Radical and Its Self-Association Promoted by van der Waals Interactions

A stable nanohoop radical (OR3) combining the structures of cycloparaphenylene and an olympicenyl radical is synthesized and isolated in the crystalline state. X-ray crystallographic analysis reveals that OR3 forms a unique head-to-tail dimer that further aggregates into a one-dimensional chain in the solid state. Variable-temperature NMR and concentration-dependent absorption measurements indicate that the π-dimer is not formed in solution. An energy decomposition analysis indicates that van der Waals interactions are the driving force for the self-association process, in contrast with other olympicenyl derivatives that favor π-dimerization. The physical properties in solution phase have been studied, and the stable cationic species obtained by one-electron chemical oxidation. This study offers a new molecular design to modulate the self-association of organic radicals for overcoming the spin-Peierls transition, and to prepare novel nanohoop compounds with spin-related properties.

Charge-Segregated Stacking Structure with Anisotropic Electric Conductivity in NIR-Absorbing and Emitting Positively Charged π-Electronic Systems

Squarylium-based π-electronic cation with an augmented dipole was synthesized by methylation of zwitterionic squarylium. The cation formed various ion pairs in combination with anions, and the ion pairs exhibited distinct photophysical properties in the dispersed state, ascribed to the formation of J- and H-aggregates. The ion pairs provided solid-state assemblies based on cation stacking. It is noteworthy that complete segregation of cations and anions was observed in a pseudo-polymorph of the ion pair with pentacyanocyclopentadienide as a π-electronic anion. In the crystalline state, the ion pairs exhibited photophysical properties and electric conductivity derived from cation stacking. In particular, the charge-segregated ion-pairing assembly induces an electric conductive pathway along the stacking axis. The charge-segregated mode and fascinating properties were derived from the reduced electrostatic repulsion between adjacent π-electronic cations via dipole-dipole interactions.

Indeno[2,1-a]fluorene-11,12-dione radical anions:synthesis,characterization and property

The one-electron reduction reactions of indeno[2,1-a]fluorene-11,12-dione ( IF ) with various alkali metals bring about the radical anion salts. The different structures and properties are characterized by single crystal X-ray diffraction, electron paramagnetic resonance (EPR) spectroscopy, superconducting quantum interference device (SQUID) measurements and physical property measurement system (PPMS). IF •- K + (18-c-6) is regarded as a one-dimensional magnetic chain through C-H-C interaction. Theoretical calculations and magnetic results prove that [ IF •- K + (15-c-5)] 2 is a dimer with an open-shell ground state. IF •- Na + (15-c-5) and IF •- K + (cryptand) are monoradical anion salts. IF 2 •- Li + possesses unique π-stack structure with an interplanar separation less than 3.46 Å, making it a semiconductor ( δ RT = 1.9 Χ 10 -4 S•cm -1 ). This work gives a wealth of insights into multifunctional radical anions, and makes the design and development of different functional radicals attractive.