Annulated 1,3,4‐Azadiphospholides: Heterocycles with Widely Tunable Optical Properties

Phosphorus heterocycles find applications in the synthesis of π‐conjugated compounds and as precursors for optoelectronic materials such as organic light‐emitting diodes (OLEDs), electronic switches, and transistors. A high‐yield, one‐pot synthesis of anionic annulated 1,3,4‐azadiphospholides from Na(OCP) and 2‐chloropyridines is presented. The synthesis proceeds without the use of transition metals and tolerates a wide range of substrates. Cyano‐substituted compounds are especially deeply colored and have absorption maxima which range from λmax=525 to 596 nm. The optical properties are dominated by the spatial separation of an electron acceptor and donor unit within one molecule (push–pull chromophore). The anionic 1,3,4‐azadiphospholides are silylated to neutral siloxy compounds with a strong blue‐shifted absorption. This reaction can be reversed by addition of fluoride ions, which allows fluoride ions to be detected in optically low concentrations. Farbenspiel: Eine ergiebige Eintopfsynthese von benzanellierten 1,3,4‐Azadiphospholiden wurde entwickelt. Diese neuen Heterocyclen haben einstellbare optische Eigenschaften, die eine Verwendung als chemische Fluoridsensoren ermöglichen.