Photophysical properties, X-ray structures, electrochemistry, and DFT computational chemistry of osmium complexes |
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Authors: | Brenden Carlson Bruce E. Eichinger John P. Bullock |
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Affiliation: | a Department of Chemistry, University of Washington, P.O. Box 351700, Seattle, WA 98195, United States b Chemistry Department, Bennington College, Bennington, VT 05201, United States c Department of Chemistry and Biochemistry, Seattle Pacific University, Seattle, WA 98119, United States |
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Abstract: | We report the synthesis of phosphorescent divalent osmium complexes of the form [Os(N-N)2(L-L) or Os(L-L)2(N-N)]2+ (PF6)2 where N-N is a derivative of 1,10-phenanthroline, and L-L is a diarsine or diphosphine ligand: 1,2-bis(dimethylphosphino)ethane, 1,2-bis(dicyclohexylphosphino)ethane, or 1,2-bis(dimethylarseno)benzene. X-ray structures have been determined, luminescent and electrochemical properties have been measured and DFT calculations have been performed on the complexes. The emission lifetime of complexes of structure Os(II)(L-L)2(N-N) are longer than the those of Os(II)(N-N)2(L-L). The DFT calculations show that there is significant mixing of the π−π∗ into the dπ−π∗ charge-transfer state for the complexes of the form Os(II)(L-L)2(N-N) resulting in a longer lived excited state. Through DFT calculations we were able to conclude that the HOMO of the complexes is a d orbital on the osmium while the LUMO is the b1(ψ) π∗ system of the phenanthroline. However, we found that the HOMO did not have the correct symmetry to enable strong charge transfer to the phenanthroline to be observed, and the strong MLCT transition observed in the spectra is the metal d HOMO(−1) to the b1 π∗ LUMO of the phenanthroline. |
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Keywords: | Osmium complexes Arsine Phosphine DFT calculations Electrochemistry X-ray crystal structures |
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