1. Comparison of 4d- and 4f-Metal Chemistry through Spectroscopic Analysis of 1,10-Phenanthroline Coordination Compounds in Solution and Embedded Polystyrene Beads
- Author
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Rodney A. Tigaa, Stephen Kuehn, Jorge H. S. K. Monteiro, Novruz G. Akhmedov, Changle Jiang, Faith E. Kidd, Joseph D. Barton, Ciersten S. Rose, Katherine Y. Franklin, Sheridan F. Herron, Franki N. Hatfield, Kaleigh G. Baisden, Abagale K. Ramsay, and Samuel K. Appiah
- Abstract
The chemistry of 4d and 4f metals was investigated at the undergraduate level in an effort to incorporate f-element chemistry in the curriculum. This was accomplished through microwave-assisted synthesis of 1,10-phenanthroline (phen) coordination compounds [Eu(phen)(subscript 3)](PF[subscript 6])[subscript 3] and [Ru(phen)(subscript 3)](PF[subscript 6])[subscript 2], and embedding the coordination compounds in polystyrene (PS) beads. Through a combination of 1-D/2-D spectroscopic techniques, the metal-phen coordination compounds in solution and in the solid state were probed. It was validated that the strong interaction between the phen ligand and Ru[superscript 2+] is due to the diffuse nature of the 4d orbitals. The interaction resulted in a low energy MLCT band, which provides opportunities for excitation at lower energies using 4d metals. In contrast, the phen ligand and core Eu[superscript 3+] 4f orbitals exhibited a weak interaction. This was supported by variable-temperature NMR (VT-NMR) measurements, which revealed relatively well-separated proton resonances with minimal differences in chemical shifts for the phen ligand at 25°C and the [Eu(phen)(subscript 3)](PF[subscript 6])[subscript 3] compound at -42°C, indicating a weak Eu-N interaction. The weak interaction resulted in the formation of an aqua-containing complex in solution evidenced by emission lifetime measurements. Despite the weak interaction, selective excitation (via ligand [pi]-[pi]* versus direct f-f) of the Eu[superscript 3+] compound allowed for color tuning, leading to the generation of a cool white light. Electron probe microanalysis (EPMA) of the metal-embedded PS beads indicated relatively monodispersed distribution of the metal complexes in the polymer.
- Published
- 2023
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