Normal & Reversed Spin Mobility in a Diradical By Electron-Vibration Coupling
Abstract New insights on the mechanisms of spin relaxation and spin mobility in connection with the structural flexibility of π-conjugated radicals are fundamental solid-state issues in organic spintronics. Here, we describe a new azobenzene-based organic diradical with a dumbbell shape in the crystal and correlate its solid-state flexibility and its spin diradical structure. X-ray temperature-dependent studies were carried out showing two main effects on heating: i) modulation of the spin distribution and of the low-to-high spin magnetic transitions; and ii) “normal” quinoidal→aromatic transformation at low temperatures driven by the intramolecular rotational motions/mobility of the azobenzene core, and a “reversed” aromatic→quinoidal change at high temperatures activated by a bicycle pedal motion in the azobenzene unit amplified by anisotropic intermolecular interactions. Sequential versus simultaneous thermal excitation of the vibrational states associated to these motions reveal a unique and unprecedented spin-vibration mechanism.