Unique Phosphorus-Based Avenues for the Tuning of Functional Materials

CONSPECTUS: Recent ground-breaking advances in synthetic chemistry have transformed main-group molecules from simple laboratory curiosities into powerful materials for a range of applications in all realms of life. Electron-accepting or-deficient materials, in particular, have been the focus of development since their generally limited availability and stability have been major hurdles in establishing new practical applications. In addition to the general requirements for the design of these materials, a deeper understanding of their inherent electronics and molecular interactions is a requirement for the successful expansion of their utility. Previously, the incorporation of electron-deficient main-group elements, such as boron, into a conjugated organic framework was considered to be an effective route toward the synthesis of high-performing electron-accepting materials. However, challenging conditions such as the need for bulky substituents for kinetic stabilization, air-free and moisture-sensitive synthesis, and restricted storage abilities have led to the investigation of other elements across the periodic table to be used in a similar vein. Lately, heavier main-group elements such as Si, Ge, P, As, Sb, Bi, S, Se, and Te have also proven to be advantageous for electron-accepting materials as they exhibit polarizable molecular orbitals that are easily accessible to electrons or nucleophiles. This has laid the foundation for materials chemistry research on a variety of applications, including optoelectronic devices such as OLEDs, organic photovoltaics, energy storage such as in batteries and capacitors, fluorescent sensors with both biological and physiological applications, organocatalysis and synthesis, and many more. Among the main-group-element-based materials, organophosphorus species are privileged as their frontier orbitals are easily altered by chemical modification or/and structural and geometrical manipulations at the phosphorus center itself, without the need for kinetic stabilization, or through electronic modification of the conjugated system. The five-membered phosphorus-based heterocycle, phosphole, is a particularly interesting motif in this context, and extensive studies on the corresponding materials have uncovered the rich fundamentals of the Sigma*-pi* interaction that imparts intriguing accepting properties while sustaining morphological and physiological stability for utilization in real-life scenarios. Moreover, beyond the Sigma*-pi* interaction in phospholes that is key to many of their acceptor properties as a material, the use of phosphorus also gives rise to easily accessible, low-lying antibonding orbitals. They pave the way for Lewis acid phosphorus species that, despite being considered to be electron-rich species in general, open up several possibilities for intriguing chemical reactivity through hypervalency. Herein, we representatively discuss some recent advancements through the various approaches that leverage the unique structures and electronics of organophosphorus species toward the design of materials with outstanding electronic, chemical, and structural properties and reactivities for the functional material world.

Automated summary

Recent advances in synthetic chemistry have led to the transformation of main-group molecules into powerful materials with a wide range of applications. Electron-deficient materials have been particularly targeted due to their limited availability and stability. Understanding their electronic and molecular interactions is crucial to expand their utility. Incorporating electron-deficient main-group elements, such as boron, into organic frameworks was considered effective, but challenging conditions have led to the exploration of other elements. Heavy main-group elements like Si, Ge, P, As, Sb, Bi, S, Se, and Te are advantageous for electron-accepting materials. Organophosphorus species, especially phosphole, have unique properties and are extensively studied in materials chemistry research. They have outstanding electronic, chemical, and structural properties, making them suitable for various applications.