Use of the Pd-promoted Extended One Pot (EOP) Synthetic Protocol for the Modular Construction of Poly-(arylene ethynylene) co-polymers [-Ar-CºC-Ar’-CºC-]n, Opto- and Electro-Responsive Materials for Advanced Technology

We report on the use of our novel multistep/ one-pot/Pd-promoted synthetic strategy, named extended one-pot (EOP), for the preparation of polymeric conjugated systems characterized by a backbone composed of regularly alternating alkyne and arylene moieties of type [-Cequivalent toC-A-Cequivalent toC-B-](n). The "A" unit (or module) is in charge of impressing mechanical strength, chemical stability and processability to the polymer, while different "B" units (or modules) have been selected to obtain polymers with different functional properties. With this "modular approach" concept, a series of co-poly(arylene ethynylene)s, of general formula [-Ar-Cequivalent toC-Ar'-Cequivalent toC-](n) [Ar = 2,5-bis(octyloxy)benzene; Ar' = 1,10-phenanthroline, hydroquinone, pyridine, tetrafluorobenzene, dithiophene, benzene, and anthracene] potentially useful for the fabrication of sensory, electroactive and light-emitting materials, have been formed. Investigations of the photophysical properties of these materials, both in solution and in the solid state, have demonstrated a large degree of variation of properties depending on the nature of Ar' and the extension of the conjugation in the polymeric backbone. This EOP synthetic protocol, with its multiple and sequential one-pot Pd-catalyzed processes, is characterized by a very low catalyst charge loading, a consistent cut-down of reaction times, ease of operation and cost with respect to conventional procedures to obtain ethynylated polymers. Moreover, although it is based on the Pd-catalyzed coupling of organostannanes and aromatic halides (Stille reaction), the EOP synthetic route optimizes and reduces the use of tin, because during the multi-step one-pot process, tin intermediates are in situ formed by complete reconversion of tin by-products generated in the course of the transformation. In addition, after formation and isolation of polymeric materials, tin-containing products are recovered and reused to form new reagents for the delivery of the alkyne moiety into the polymer backbone.[...]