Condensed Phenoxazine Dimer and Its Radical Cation

Synthesis and Properties of Cyclic π-Conjugated Molecules and Their Dication and Monoradical Cation

We synthesized cyclic π-conjugated molecules by double Friedel-Crafts reaction of amino group-substituted 1,2-bis(2-phenylethynyl)benzene with Meldrum's acid derivative. The structures of the cyclic π-conjugated molecules were determined by single-crystal X-ray structure analysis. The oxidation of the dimethylamino group-substituted π-conjugated molecule with NOBF4 gave a closed-shell dication that is stable at >210 °C. The monoradical cation of the di(4-methoxyphenyl)amino group-substituted π-conjugated molecule is stable in dichloromethane solution (half-life of nearly 15 days) and shows near-infrared absorption.

Planar Tetraindolodipleiadiene via Zirconium-Promoted Intramolecular Indolyl C4-H Homocoupling

A novel N-rimmed PAH molecule containing a dipleiadiene core (TIDP) was designed and synthesized from indole, wherein a ZrCl₄-promoted intramolecular C4-H homocoupling reaction of the indole moieties was the key approach. TIDP exhibited a nearly full planar structure and antiaromaticity of the two embedded heptagonal rings. The extremely stable radical cation TIDP^•+·PF₆^- was isolated quantitatively by oxidation with AgPF₆.

S,C,C- and O,C,C-Bridged Triarylamines and Their Persistent Radical Cations

This work reports the synthesis, crystal structures, and electronic properties of structurally constrained S,C,C- and O,C,C-bridged triarylamine derivatives and their persistent radical cations. O,C,C-Bridged triphenylamines and a dinaphthylphenylamine were obtained through a straightforward synthetic protocol. Similar to a previously reported S,C,C-bridged triphenylamine, the O,C,C-bridged triarylamines were easily oxidized to afford the corresponding radical cations, which were obtained as hexachloroantimonate salts. X-ray crystallographic analyses showed almost planar structures for these O,C,C-bridged triarylamine radical cations, which represent new members of the family of planar triarylamine radical cations without substituents on the aryl rings. Detailed investigations of the electronic properties of the S,C,C- and O,C,C-bridged triarylamine radical cations demonstrated that the spin and positive charge are sufficiently delocalized over the planar triarylamine scaffolds. The results provide the following insights into the effects of the bridging unit (sulfur vs oxygen) and the dibenzo-annulation on the spin delocalization in the bridged triarylamine radical cations: (1) An effective decrease of the spin density on the nitrogen atom is observed for the sulfur bridge relative to the oxygen bridge; and (2) a moderate decrease of the spin density on the oxygen atom rather than the nitrogen atom is induced by the dibenzo-annulation.