5 years ago

Silver(I) Clusters with Carba-closo-dodecaboranylethynyl Ligands: Synthesis, Structure, and Phosphorescence

Silver(I) Clusters with Carba-closo-dodecaboranylethynyl Ligands: Synthesis, Structure, and Phosphorescence
Natalia Wolf, Andreas Steffen, Rebecca Renner, Michael Hailmann, Maik Finze, Benjamin Hupp
Salts of anionic silver(I) clusters with the carba-closo-dodecaboranylethynyl ligand were obtained from {Ag2(12-C≡C-closo-1-CB11H11)}n, selected pyridines, and [Et4N]Cl or [Ph4P]Br. Salts of octahedral silver(I) clusters [Et4N]2[Ag6(12-C≡C-closo-1-CB11H11)4(4-X-C5H5N)x] were formed with pyridine (X=H, x=8), 4-methylpyridine (X=Me, x=8), and 4-cyanopyridine (X=CN, x=10). In contrast, 3,5-lutidine (3,5-Me2Py) did not result in salts of dianionic clusters, even in the presence of excess of [Et4N]Cl or [Ph4P]Br; instead salts of monoanionic AgI7 clusters, [Et4N][Ag7(12-C≡C-closo-1-CB11H11)4(3,5-Me2Py)9] and [Ph4P][Ag7(12-C≡C-closo-1-CB11H11)4(3,5-Me2Py)13] were obtained. The AgI7 cluster is pentagonal bipyramidal in the former, but is an edge-capped octahedron in the latter. The 4-methylpyridine and 3,5-lutidine complexes show green phosphorescence at room temperature. Although argentophilic interactions give rise to sufficient spin–orbit coupling for intersystem crossing S1Tn and moderate-to-high radiative rate constants, time-resolved measurements indicate that the quantum yields are greatly influenced by the pyridine ligands, which mainly determine the non-radiative rate constants. In addition, the crystal structures of [Ag16(12-C≡C-closo-1-CB11H11)8(Py)9.25(CH3CN)2(CH2Cl2)0.75]⋅CH2Cl2, [Ag8(12-C≡C-closo-1-CB11H11)4(Py)12], [Ag10(12-C≡C-closo-1-CB11H11)4(4-MePy)10Br2], [Ag7(12-C≡C-closo-1-CB11H11)3(4-tBuPy)11Cl]⋅(4-tBuPy), and [Ag9(12-C≡C-closo-1-CB11H11)4(3,5-Me2Py)11Cl] were elucidated. The silver lining: Neutral, monoanionic, and dianionic silver(I) clusters stabilized by carba-closo-dodecaboranylethynyl and pyridine ligands were obtained with organic cations (see figure). Selected clusters were studied by photoluminescence spectroscopy and found to be room-temperature phosphorescent. The quantum yields were strongly influenced by the pyridine ligands.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201702515

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