Ternary SeRuCu clusters: Facile synthesis, electrochemistry, and UV/Vis absorption

•A series of face-capping and edge-bridging SeRu5 clusters that contain the CuX fragment.•A successive redox potential shift of the SeRu5-based clusters tuned by the incoming CuX fragment.•Ternary SeRuCu clusters exhibiting semiconducting behaviors with tunable energy gaps.

New ternary SeRuCu octahedral-based complexes, namely, CuX-capped SeRu5 clusters [SeRu5(CO)14(μ3-CuX)]2− (2a–2c; X = Cl, Br, I), bis-CuX-capped SeRu5 clusters [SeRu5(CO)14(μ3-CuX)2]2− (3a, 3b; X = Cl, Br), Cu4X2-bridged di-SeRu5 clusters [{SeRu5(CO)14}2(μ6-Cu4X2)]2− (4a, 4b; X = Cl, Br), and bis-CuX-incorporated Se2Ru4 clusters [Se2Ru4(CO)10(μ-CuX)2]2− (5a–5c; X = Cl, Br, I), were prepared from the reaction of the binary cluster [SeRu5(CO)14]2− (1) with CuX under appropriate conditions. Their solid-state packing formed cluster-based 1D-supramolecular chains, which were stabilized by CH⋯X/Y (X = halides; Y = O) H-bonding between CuX/COs of cluster anions and the CH moieties of the [PPh4]+ or [PPN]+ cations. In addition, electrochemical studies showed that the successive anodic shifts were found for 1–4b, tuned by the incoming CuBr fragments introduced into the parent SeRu5 cluster, supported by their decreasing HOMO levels and increasing ionization energies. Solid-state diffuse reflectance spectra showed these SeRuCu complexes exhibited semiconducting behaviors with the low and tunable energy gaps of 0.82–1.08 eV. Significantly, the solid-state absorptions of 2b and 4b were red-shifted compared with the corresponding Te analogues, which was explained by the larger numbers of the density of states (DOS) close to the HOMO for the selenide cases.

Graphical abstractThe structures and electronic properties of a new series of SeRuCu carbonyl clusters were studied by crystallographic, spectroscopic, electrochemical, and computational analyses.Figure optionsDownload full-size imageDownload as PowerPoint slide