Emissive Ln(III)-Hg(II)/Pb(II) Coordination Polymers with Heteropolymeric 1-D Structures Synthesized Mechanochemically Using a Hard-Soft Acid-Base Mismatch Strategy

The mechanochemical synthesis of a family of heterobimetallic Ln(III)-M(II) coordination polymers of the form [Ln(OAc)2(OH2)3](MBr3)]·xH2O (Ln = Eu, Tb, 50:50 Eu/Tb; LnHg: M = Hg, x = 1; LnPb: M = Pb, x = 0) is described. They are formed via the anion-exchange reaction between lanthanide(III) bromide and metal(II) acetate salts and driven by a mismatch in hard-soft acid-base character. The crystal structure of EuHg revealed a heteropolymeric 1-D structure, with cationic acetate-bridged and anionic bromide-bridged chains forming parallel arrays; IR, Raman, and photoluminescence spectroscopic data of LnPb strongly suggested similarity with the LnHg compounds. The analogous reaction with EuCl3·6H2O and Hg(OAc)2 forms an isostructural material, but substituting Pb(OAc)2 generates [Eu(OAc)2(OH2)3]Cl and PbCl2 instead of a mixed-metal product comparable to LnPb. An N,N-dimethylformamide (DMF) solvate [Eu(OAc)2(DMF)3](PbBr3)] (EuPb·DMF) was structurally characterized, showing the same heteropolymeric motif as EuHg and resembling an organic-inorganic lead-halide perovskite due the anionic chain of face-sharing bromoplumbate(II) octahedra. Photoluminescence properties of the compounds, including lifetime measurements and Tb(III)→Eu(III) energy transfer parameters for the LnM 50:50 Eu/Tb solid-solutions are described.

Synthesis, Crystal Structure, and Photoluminescent Properties of a Series of LnIII–CuI Heterometallic Coordination Polymers Based on Cu4I3 Clusters and Ln–ina Rod Units

A novel series of LnIII–CuI heterometallic coordination polymers (HCPs) {[Ln2Cu4I3(ina)7(DMA)2]n·nDMA, Ln = La (1), Ce (2), Pr (3) Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9) Ho (10), Er (11), Yb (12), Hina = isonicotinic acid, DMA = N,N-dimethylacetamide} were synthesised by a solvothermal reaction. The structures of compounds 1–12 were characterised by elemental analysis, FT-IR spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. Single crystal X-ray diffraction studies revealed that 1–12 are isomorphous and are 3D heterometallic coordination polymers based on inorganic Cu4I3 clusters and Ln2(ina)7(DMA) rod units. In addition, the luminescent properties of compounds 5–9 have been investigated in detail. All of them exhibited green light emission due to the synergistic effects of characteristic emissions of lanthanide ions and iodide-to-copper charge transfer.