Open for Bismuth: Main Group Metal-to-Ligand Charge Transfer

Abstract

The synthesis, characterization, and photophysical properties of 4and 6-coordinate Bi 3+ coordination complexes are reported. Bi(bzq) 3 ( 1) and [Bi(bzq) 2 ]Br (2) (bzq = benzo[h]quinoline) are synthesized by reaction of 9-Libzq with BiCl 3 and BiBr 3 , respectively. Absorption spectroscopy, electrochemistry, and DFT studies suggest that 1 has 42% Bi 6s character in its highest-occupied molecular orbital (HOMO) as a result of six σ* interactions with the bzq ligands. Excitation of 1 at 450 nm results in a broad emission feature at 520 nm, which is rationalized as a metal-to-ligand charge transfer (MLCT) and phosphorescent emission resulting from bismuth-mediated intersystem crossing (ISC) to a triplet excited state. This excited state revealed a 35 μs lifetime and was quenched in the presence of oxygen. These results demonstrate that useful optoelectronic properties of Bi 3+ can be accessed through hypercoordination with covalent organobismuth interactions that mimic the electronic structure of lead perovskites.

Luminescent First-Row Transition Metal Complexes

“…On the one hand, this includes comparatively abundant second- and third-row transition metals (for example Zr, , Mo, ,,, or W ,,,, ) or f-elements (for example Ce , ). On the other hand, molecular complexes of abundant main group elements are now attracting increasing attention as luminophores and provide additional insight into how nonradiative relaxation can be tamed. − At the same time, further developments of precious metal-based complexes (for example, Ru, ,, Rh, , Re, − Ir, − or Pt − ) have significantly advanced the field of inorganic photophysics and photochemistry. Regardless of whether complexes of d-, f-, or main group elements are considered, the interplay between synthetic, spectroscopic, and computational work seems crucial for the development of new designer luminophores.…”

Harnessing Bismuth Coordination Chemistry to Achieve Bright, Long-Lived Organic Phosphorescence

“…Bi-based materials, in particular, are an attractive target for materials design. The global availability (i.e., low cost) and relatively low toxicity of Bi compared to other heavy elements, coupled with its unique lone-pair electron effects, flexible coordination geometries, and potential for structural regulation of the photophysical properties, are highly desirable. − Bi 3+ exhibits a closed-shell electron configuration like the d 10 metal ions, with the general electron configuration of n d 10 ( n + 1)­s 2 , making it amenable for achieving ligand-based emission in hybrid systems. − Indeed, the incorporation of heavy elements into π-conjugated materials is known to enhance the probability of accessing the triplet state of organic emitters, and hence phosphorescence, by increasing the rate of intersystem crossing (ISC). − The development of stable, long-lived phosphorescent emitters utilizing Bi may thus provide new design strategies for luminescent materials, with applications in light-emitting diodes and bioimaging. , Additionally, the broadband emission of Bi-based materials, coupled with the linelike emission of metals such as the Ln ions, provides further opportunities for dual emission, the possibility of color tuning, and/or white-light emission. − …”

Zinc-Based Metal–Organic Framework with MLCT Properties as an Efficient Electrochemiluminescence Probe for Trace Detection of Trenbolone

“…The metal–organic framework (MOF) is a porous material with special topological and designable pore structures, which is widely used in ECL sensing analysis. − As traditional ECL emitters, polycyclic aromatic hydrocarbons (PAHs) and their derivatives have received great attention due to their high quantum yield and good optoelectronic characteristics. , However, they will induce an aggregation-induced quenching (ACQ) effect, resulting in limited ECL efficiency. − Encouragingly, PAHs and their derivatives as ligands can eliminate the ACQ effect caused by π–π stacking through their coordination in the MOF. At the same time, the designed MOF has the metal-to-ligand charge-transfer (MLCT) peculiarity, which can transfer the energy of metal ions from their outermost molecular orbital to the lowest unoccupied molecular orbital (LUMO) of ligands, thus achieving stable and efficient luminescence. , Among PAH derivatives, 3,4,9,10-perylene tetracarboxylic (PTC) can be used as an ideal ligand for the assembly of a luminescent MOF due to the high specific surface area, excellent conductivity, and stable ECL properties of persulfate (S 2 O 8 2– ). − …”

“…At the same time, the designed MOF has the metal-to-ligand charge-transfer (MLCT) peculiarity, which can transfer the energy of metal ions from their outermost molecular orbital to the lowest unoccupied molecular orbital (LUMO) of ligands, thus achieving stable and efficient luminescence. 23,24 Among PAH derivatives, 3,4,9,10-perylene tetracarboxylic (PTC) can be used as an ideal ligand for the assembly of a luminescent MOF due to the high specific surface area, excellent conductivity, and stable ECL properties of persulfate (S 2 O 8…”