Near-White Light Emission from Lead(II) Metal–Organic Frameworks

Abstract

Reaction of bpy (bpy = 4,4'-bipyridine) with Pb(OAc)·3HO in DMF (DMF = dimethylformamide) afforded a metal-organic framework (MOF), [Pb(μ-bpy)(μ-OCCH)(μ-OCCH)]·HO (1). Reaction of bpy with Pb(OCCF) in a methanol and chloroform mixture furnished another MOF, [Pb(μ-bpy)(μ-OCCF)]·/CHCl (2). However, the reaction of bpy with Pb(OAc)·3HO in the presence of trifluoroacetic acid in a similar reaction condition yielded a hydrogen-bonded zwitter-ionic complex of Pb(II), [Pb(bpy-H)(OCCF)] (3). All compounds have been characterized by single crystal X-ray crystallography, FT-IR, and H NMR spectroscopies. Compound 1 forms four heptacoordinated Pb(II) joined by (OCCH)-O- linkages, resulting in a 3D noninterpenetrated MOF net with a four-connected uninodal sra (SrAl) topology. However, in 2, tetra-connected Pb(OCCF) cluster units are linked further through eight bpy ligands to furnish a doubly interpenetrated MOF with a new topology but having the very similar connectivity of 1, whereas 3 forms a zigzag hydrogen-bonded chain structure. The variation of carboxylate anions, pH of the reaction medium, and the ratio of the reactants profoundly affected the final topological structure of the compounds synthesized. The solid-state photoluminescence of 1-3 was investigated at room temperature. Interestingly 1, 2, and 3 achieved close to white light emission when excited at 329, 376, and 330 nm, respectively. The systematic understanding of the photophysical properties of analogous Pb-based compounds may open new perspectives for developing single-phase white-light-emitting materials using Pb(II) based MOFs.

Intrinsic White‐Light‐Emitting Metal–Organic Frameworks with Structurally Deformable Secondary Building Units

“…However, the high demand for RE elements has led to a dramatic 49‐fold price increase from 2001 to 2011 . Other white‐light‐emitting MOFs either exhibit ligand‐based luminescence or are based on metal‐to‐ligand/ligand‐to‐metal charge transfer (MLCT/LMCT) or a combination of both . Among them, very few emit broadband white‐light emission spanning the entire visible spectrum with high color‐rendering index (CRI) …”

Intrinsic White‐Light‐Emitting Metal–Organic Frameworks with Structurally Deformable Secondary Building Units

“…[27] Other white-lightemitting MOFs either exhibit ligand-based luminescence or are based on metal-to-ligand/ligand-to-metal charge transfer (MLCT/LMCT) or acombination of both. [28,29] Among them, very few emit broadband white-light emission spanning the entire visible spectrum with high color-rendering index (CRI). [30] Herein, we describe the incorporation of structurally deformable lead halide units,w hich are often observed in organolead halide perovskites,i nto MOFs.…”

5,5′‐(1,4‐Dioxo‐1,2,3,4‐tetrahydrophthalazine‐6,7‐diyl)bis(oxy)diisophthalate‐Based Coordination Polymers and their TNP Sensing Ability

“…Due to the molecular close packing, and the occurrence of inter(intra)molecular excited‐state proton transfer (IESPT), most acylhydrazidate‐based coordination polymers do not emit light. However, we note that in these limited photoluminescence acylhydrazidate‐based coordination polymers, most contain the heavy‐metal centers as Pb 2+ . Even though they also exhibit a close packing network structure, they still emit light.…”