PbI4Cu2(PPh3)4: A heterometallic iodide with unusual cis-divacant octahedral coordination sphere for lead: Synthesis, structure, red-infrared fluorescence and theoretical studies

A new heterometallic iodide, PbI4Cu2(PPh3)4, was synthesized by reactions of PbI2, CuI and triphenylphosphine (PPh3) in DMF solution. The single-crystal X-ray diffraction analyses show that Pb(II) center adopts an unusual cis  -divacant octahedral geometry. Crystal data: triclinic, space group P1¯, a=12.3455(2)Å, b=13.8673(1)Å, c=21.3421(1)Å, α=106.623(4)°α=106.623(4)°, β=103.478(6)°β=103.478(6)°, γ=93.574(5)°γ=93.574(5)°, V=3371.83(6)Å3 and Z=2Z=2. Density function theory (DFT) calculations and fragment orbital interaction analyses reveal the presence of a three-center four-electron (3c–4e) hypervalent bonding about lead; and the formation of the unusual cis-divacant [PbI4]2− octahedron is energetically favorable. The title yellow compound has an optical bandgap of 2.69 eV and shows remarkable red-infrared fluorescence emission at 732 nm with lifetime of 24 μs which is assigned as an iodine 5p-lead 6s to PPh3-lead 6p charge transfer (XM-LM-CT).

Graphical abstractA new heterometallic iodide, PbI4Cu2(PPh3)4, was synthesized by reactions of PbI2, CuI and triphenylphosphine (PPh3) in DMF solution. The single-crystal X-ray diffraction analyses show that Pb(II) center adopts an unusual cis-divacant octahedral geometry. DFT calculations and fragment orbital interaction analyses reveal the presence of a 3c-4e hypervalent bonding about lead; and the formation of the unusual cis-divacant [PbI4]2− octahedron is energetically favorable. The title yellow compound has an optical bandgap of 2.69 eV and shows remarkable red-infrared fluorescence emission.Figure optionsDownload full-size imageDownload as PowerPoint slide