A solid-state effect responsible for an organic quintet state at room temperature and ambient pressure.

A stable organic diradicaloid with an intermolecular quintet at room temperature as a polycrystalline solid is studied. The conclusion is supported by the observation of the ΔMs = ±2 forbidden transition, electron spin resonance (ESR) simulations, and density functional theory (DFT) calculations. In addition, the molecule, as the active component of a device, is an outstanding near-infrared photodetector with detectivity over 10(11) cm Hz(1/2) W(-1) at 1200 nm.