Iminoborane units add inorganic flavor to polymers

Chemists in Germany have reported a novel inorganic–organic hybrid polymer that can be regarded as an amino borane analog of poly(p-phenylene vinylene), a semiconducting polymer commonly used in light-emitting diodes, field-effect transistors, solar cells, and other optoelectronic devices (Angew. Chem. Int. Ed. 2017, DOI: 10.1002/anie.201612476). Researchers are increasingly taking advantage of the technique of substituting selected C=C units in conjugated organic frameworks with structurally equivalent B=N units to create materials with new properties and functions. Because π-electron conjugation is often disrupted when substituting B=N for C=C, Holger Helten and coworkers of RWTH Aachen University became curious whether they could create a BN analog of poly(p-phenylene vinylene) and whether the polymer’s π-conjugation would persist. The researchers prepared the BN analog, poly(p-phenylene iminoborane), by a polycondensation reaction of boron- and silylamine-disubstituted benzenes. The team’s photophysical studies on the polymer and a series of oligomers provided evidence of π-conjugation across the B=N linkages, although it is less pronounced than for all-carbon poly(p-phenylene vinylene). The Aachen researchers are now further exploring the concept of BN doping of conjugated polymers with an eye toward developing new organic electronics applications.