Synthesis of Main Group Compounds and Materials with Novel Structures and Optoelectronic Properties

Case Western Reserve University, Cleveland OH

Investigators

Abstract

With the support of the Chemical Synthesis program of the Division of Chemistry, Professor John Protasiewicz and his students at the Department of Chemistry at Case Western Reserve University are preparing compounds with P=C-containing extended pi-electron systems. The inclusion of P=C units permits the optical and electronic properties of the material to be tuned in order to maximize the behavior of the material. A motivation for these studies is a need for economical means to manufacture highly efficient lighting and displays. Methods that utilize inexpensive and abundant elements and ones that minimize the formation of wasteful and toxic byproducts are especially attractive. This project envisions the preparation of low cost/lightweight/processable plastics and materials related to light emitting technology. Examples, include polymers, molecular electronics, light emitting diodes, photovoltaics, and flexible electronics. The students trained and educated as part of this research program are being prepared to enter tomorrow's skilled workforce in industry and education. In addition to the technical broader impacts related to advanced manufacturing, Professor Protasiewicz will co-organize and run programs directed at raising awareness of mental health issues among graduate students and faculty. Reactive main group systems will be synthesized and their photophysical properties interrogated to advance and create new paradigms in main group photophysical chemistry. This work explores several interconnected research threads, inspired from previous studies on luminescent 1,3-benzoxaphospholes and 1,3-benzazaphospholes. A new class of photoluminescent compounds (phospha-azulenes) bearing P=C bonds will be prepared to display fluorescence from the S2 (not S1) excited state, thus breaking Kasha's rule. Anti-Kasha compounds are rare and have desirable photophysical properties. Unconventional hydrogen bonding between N-heterocyclic carbenes and fluorescent secondary amines will be exploited to develop the supramolecular chemistry of dicarbenes that can undergo hydrogen bonding to a fluorophores containing two NH functional groups, which will offer new opportunities to develop materials that could act as turn-on fluorescent sensors for select applications. Previous studies also uncovered an unusual reaction that converts ortho-phosphinophenol to benzodioxaphosphole. This process involves removing 6 hydrogen atoms and making new PP and PO bonds. This process will be extended to other types of bonds and and attempts will be made to make the process catalytic. The metal-free systems to be developed in this research move away from previously reported strategies based on expensive and/or toxic transition metals and concentrates on elements that are less toxic and more earth abundant. Combined, these efforts aim to advance and showcase the advantages that main group elements can offer to the greater field of optoelectronic and structural materials. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.