Next Generation Phosphorescent Tellurophene Monomers and Polymers
Preparatory and Physical Chemistry of Polymers
Final Report Abstract
In this research project a series of monomeric and dimeric extended π-conjugated Te-heterocycles have been synthesized by sequential alkyne insertion to yield zirconacycle precursors and final Zr/Te transmetallation. Additionally, it was shown that the implementation of two functional groups within one tellurophene unit can in principle be used as a building block for homo polytellurophenes with low molecular weight. However, protodeboronation remain a major challenge in the formation of such polymers. All newly synthesized tellurophenes display phosphorescence in solution and/or in the solid state. Besides observed crystallization induced emission and vapochromism in selected compounds, a key finding is the systematic bathochromic shift in the emission color in deoxygenated THF solutions of the dimeric tellurophenes from green to deep-red with added arene units (e.g. from a benzo to pyrenyl based backbone). In addition, the high molar absorptivities of the larger telluroacenes give rise to brighter emission. Time-dependant density functional theory computations not only determined that the origin of the phosphorescence is stemming from participation of the Te atoms in the excitation processes, but also proved to be a valuable tool in forecasting phoshorescence energies of larger telluroacenes. The computations show that the emission maximum can be shifted towards the near IR region by further extending the π-conjugated backbone, but care has to taken by the relative arrangement of the fused acene units. The synthetic approach used within this study is not limited to tellurophenes, but can also be extended to other p-block elements to obtain electron-rich (e.g. P, S, Se and Te) or electrondeficient (e.g. B) heteroacenes, showing the generality of the synthesis. The overall low quantum yields remain a challenge for the design of efficient OLED fabrications on tellurophene basis and future work will concentrate to develop dimeric tellurophene units with short alkyl or alkenyl linkers to obtain tellurophene moieties with a locked rotation along the linker to yield enhanced phosphorescence. In a separate project, the bonding scenario in a series of low oxidation state Ge species linked by an electron donating anionic N-heterocyclic olefin (MeIPrCH–) have been investigated. All investigated compounds contain the general structural feature of a Ge2C2 core, which revealed weakly repulsive Ge-Ge interactions despite short Ge-Ge distances. In contrast, the computationally modelled cyclic Ge(I) dimer showed a rare ‘bent’ Ge-Ge σ- bond. Furthermore, it was shown that the anionic N-heterocyclic olefin ligand can easily migrate to form various intermediates with final 1,2-migration.
Publications
- (2019) A Modular Approach to Phosphorescent π-Extended Heteroacenes. Inorganic chemistry 58 (19) 13323–13336
Hupf, Emanuel; Tsuchiya, Yuki; Moffat, Wayne; Xu, Letian; Hirai, Masato; Zhou, Yuqiao; Ferguson, Michael J.; McDonald, Robert; Murai, Toshiaki; He, Gang; Rivard, Eric
(See online at https://doi.org/10.1021/acs.inorgchem.9b02213) - “Aerobic Solid State Red Phosphorescence from Benzobismole Monomers and Patternable Self-Assembled Block Copolymers” Angew. Chem. Int. Ed. 2018, 57, 14841-14846
Parke, S. M.; Hupf, E.; Matharu, G. K.; de Aguiar, I.; Xu, L.; Yu, H.; Boone, M. P.; de Souza, G. L. C.; McDonald, R.; Ferguson, M. J.; He, G.; Brown, A.; Rivard, E.
(See online at https://doi.org/10.1002/anie.201809357) - “Understanding the Origin of Phosphorescence in Bismoles: A Synthetic and Computational Study” Inorg. Chem. 2018, 57, 7536-7549
Parke, S. M.; Narreto, M. A. B.; Hupf, E.; McDonald, R.; Ferguson, M. J.; Hegmann, F. A.; Rivard, E.
(See online at https://doi.org/10.1021/acs.inorgchem.8b00149) - “Linking Low-coordinate Ge(II) Centers via Bridging Anionic N-Heterocyclic Olefin Ligands” Inorg. Chem. 2019
Hupf, E.; Kaiser, F.; Lummis, Paul A.; Roy, M. M. D.; McDonald, R.; Ferguson, M. J.; Kühn, F. E.; Rivard, E.
(See online at https://doi.org/10.1021/acs.inorgchem.9b01449)
