From Model Compounds to Extended π-Conjugated Systems: Synthesis and Properties of Dithieno[3,2-b:2′,3′-d]phospholes

• Published in: Chemistry : a European journal 2005-08, Vol.11 (16), p.4687-4699
• Main Authors: Baumgartner, Thomas, Bergmans, Werner, Kárpáti, Tamás, Neumann, Toni, Nieger, Martin, Nyulászi, László
• Format: Article
• Language: English
• Subjects: density functional calculations; luminescence; molecular electronics; optical properties; phosphorus heterocycles
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200500152

To explore their suitability for applications in molecular optoelectronics and as sensory materials, novel dithieno[3,2‐b:2′,3′‐d]phospholes have been synthesized and their reactivity and properties investigated. An efficient two‐step synthesis allowed for a modular assembly of differently functionalized compounds. The dithieno[3,2‐b:2′,3′‐d]phosphole system exhibits extraordinary optoelectronic properties with respect to wavelength, intensity, and tunability. Owing to the nucleophilic nature of the central phosphorus atom, its significant electronic influence on the conjugated π system can be altered selectively by chemically facile modifications such as oxidation or complexation with Lewis acids or transition metals. All the dithienophosphole species presented show very strong blue photoluminescence with excellent quantum yield efficiencies supporting their potential utility as blue‐light emitting components in organic light emitting diodes (OLEDs). Furthermore, depending on the electronic nature of the phosphorus center, the materials exhibit distinctive optoelectronic properties suggesting that the dithieno[3,2‐b:2′,3′‐d]phosphole system may be useful as sensory material. Theoretical calculations, including time‐dependent DFT methods, revealed the excellent predictability of the structures and optoelectronic properties of the functionalized dithienophospholes allowing the design of future dithieno[3,2‐b:2′,3′‐d]phosphole‐based materials to be ”stream‐lined”. By using tin‐functionalized dithienophosphole monomers, a strategy, which involves Stille coupling, towards extended π‐conjugated materials with significantly redshifted optoelectronic properties is also presented. Blue light—easily tunable: Incorporation of a phosphorus bridge into a bithienyl moiety gives access to a novel, strong blue‐luminescent system; its optoelectronic properties can be selectively manipulated by simple chemical modifications in several different ways (see figure). Owing to the rigid nature of the dithienophosphole structure, the results of the functionalization can be predicted conveniently by means of TD‐DFT calculations.