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Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of Phosphorus(I)
Published on: November 22, 2016
Pi-conjugated phosphasilenes stabilized by fused-ring bulky groups.
Baolin Li1, Tsukasa Matsuo, Daisuke Hashizume
1Functional Elemento-Organic Chemistry Unit, RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Journal of the American Chemical Society
|September 1, 2009
Summary
New phosphasilenes featuring aryl groups on silicon were synthesized. The unique structure, stabilized by octaethyl-s-hydrindacen-4-yl (Eind) groups, enables extended pi-conjugation, confirmed by DFT calculations and spectroscopy.
Area of Science:
- Organosilicon Chemistry
- Materials Science
- Computational Chemistry
Background:
- Pi-conjugated systems are crucial for organic electronics and materials science.
- Phosphasilenes, compounds containing a silicon-phosphorus double bond, offer unique electronic properties.
- Stabilization of reactive species is key to their synthesis and application.
Purpose of the Study:
- To synthesize novel pi-conjugated phosphasilenes with diverse aryl substituents.
- To investigate the structural, electronic, and optical properties of these compounds.
- To explore the role of the octaethyl-s-hydrindacen-4-yl (Eind) group in stabilizing the phosphasilene framework.
Main Methods:
- Synthesis of phosphasilenes utilizing the 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (Eind) ligand.
- X-ray structural analysis to determine molecular geometry and pi-framework planarity.
- UV-Vis spectroscopy to observe pi-pi* absorptions and assess conjugation length.
- Density Functional Theory (DFT) calculations to analyze frontier molecular orbitals and conjugation pathways.
- Electrochemical measurements to characterize redox properties.
Main Results:
- Successful synthesis of phosphasilenes with various aryl groups on silicon, stabilized by the Eind moiety.
- X-ray analysis revealed a highly coplanar pi-framework, with perpendicularly oriented Eind groups providing steric protection.
- Strong pi-pi* absorptions indicated extended pi-conjugation across the molecular skeleton.
- DFT calculations confirmed significant conjugation between the silicon-phosphorus (Si-P) 3p(pi) and carbon pi-electron systems in the Lowest Unoccupied Molecular Orbital (LUMO).
Conclusions:
- The Eind group effectively stabilizes pi-conjugated phosphasilenes, enabling the formation of planar structures.
- Extended pi-conjugation is achieved, leading to characteristic optical absorption properties.
- The electronic structure demonstrates significant interaction between silicon-phosphorus and carbon pi-systems, relevant for optoelectronic applications.
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