An Unexpected “Step-Conjugated” Biphosphole via Unique P–P Bond Formation

Zisu Wang, Nayanthara Asok, Joshua Gaffen, Yael Gottlieb, Wenhua Bi, Chris Gendy, Roman Dobrovetsky*, Thomas Baumgartner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The synthesis of a π-conjugated organophosphorus species with bridging P–P unit is reported. Because of the pyramidal geometry of the phosphorus centers, the molecular scaffold provides intriguing electronic communication throughout the three-dimensional structure via π-σ-π conjugation in stepwise fashion. The dimeric species was serendipitously found to be accessible via a reaction of the corresponding P-amino-phosphole precursor through mediation with the hard Lewis acid BF3. We provide detailed mechanistic studies toward a suitable reaction mechanism that was also verified via computational means. Moreover, we elaborate the utility of the biphosphole via phosphorus functionalization that lends further proof for the step conjugation provided by the unique phosphorus-based molecular architecture. Fundamental chemistry lays the foundation for future innovation with considerable impact on next-generation technologies. Main-group chemistry in particular provides a unique angle with regard to structure and bonding, which makes it an intriguing state-of-the-art avenue for the development of readily accessible advanced materials with significantly value-added functionality, that is, optical and electronic properties. The need for innovative molecular architectures is particularly evident in the rapidly accelerating development of conjugated organic building blocks because their high utility for a variety of sustainable energy applications is now well established. Herein, we report a unique type of phosphorus-based “step-conjugated” building block via an unexpected reaction that we have elucidated mechanistically in our studies. Reaction of a P-amino-dithienophosphole with the hard Lewis acid, BF3, leads to a dimeric species via a P–P bond-forming reaction, as supported through systematic mechanistic studies. Because of the inherent pyramidal geometry of the phosphorus centers, the dimer shows extended step-like conjugation through the scaffold via π-σ-π conjugation, which makes it an intriguing new building block for organic hybrid materials.

Original languageEnglish
Pages (from-to)2628-2643
Number of pages16
JournalChem
Volume4
Issue number11
DOIs
StatePublished - 8 Nov 2018

Funding

FundersFunder number
Israeli Ministry of Science, Technology, and Space
Natural Sciences and Engineering Research Council of Canada
Canada Foundation for Innovation
Canada Research Chairs
Alberta Innovates

    Keywords

    • Lewis-acid-mediated coupling reaction
    • SDG7: Affordable and clean energy
    • biphosphole
    • conjugated materials
    • main-group chemistry

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