Highly Emissive Cyclometalated Rhenium Metallacycles: Structure−Luminescence Relationship

Abstract

We report on a series of new self-assembled cyclometalated dirhenium(I) metallacyclic complexes via an unprecedented rhenium-mediated C-H bond activation and the relationship between their structures and luminescence properties.

A Luminescent Rhenium(I) Metallacycle with Oxygen and Nitrogen Donor Atoms: Photophysical and Theoretical Studies

“…The product is air‐ and moisture‐stable and is soluble in polar organic solvents. A recent review on Re I metallacycles15 has revealed that all dinuclear Re I complexes are bridged through O , O ‐,11b N , N ‐8 or N , C ‐donor atoms 8. In fact, multinuclear Re I assemblies with asymmetric coordination environments are rare 15,16…”

“…Because of the large spin–orbit coupling (SOC) and hence efficient intersystem crossing (ISC) shown by the Re I metal centre, structureless and broad phosphorescent emission from the lowest‐energy triplet excited state is most often observed 7. Such a deactivation route from the triplet metal‐to‐ligand charge‐transfer ( 3 MLCT) state is also attributed to 1) a radiative lifetime in the nanosecond range, 2) a prominent rigidochromism and 3) emission quenching by dioxygen 7,8…”

“…Notable examples of highly phosphorescent Re I metallacycles include N,C‐donor‐containing Re I metallacyclophanes ( λ max = 370 nm; Φ em up to at least 0.48) exhibiting 3 MLCT emission that is relatively long‐lived ( τ > 4.13 μs) 8. Surprisingly, an analogous N , N ‐donor assembly shows weak ns‐range inter‐ligand 3 π–π* emission ( τ = 0.18 ns) with a negligible contribution from the 3 MLCT states ( λ max = 372 nm, Φ em = 0.01) 8. Thus, we asked the question: is it possible to prepare a Re I metallacycle with simultaneous multiple emissive excited states that are thermally inaccessible from d π –d σ * excited states and show efficient luminescence?…”

Self‐Assembly of Oxamidato‐Chelated ReI‐ and MnI‐Based Flexible Dinuclear Horse‐Stirrup‐Like Metallacycles

“…[15,[27][28][29][30][31] For the construction of such dirhenium metallacycles, bis(chelating) organic clips are usually utilized in combination with flexible dipyridyl linkers. [27,30] Owing to their efficacy in different fields such as luminescent sensors, imaging, and photocatalytic CO 2 reduction, Re I -based complexes continue to attract considerable interest for various modern applications. [32][33][34][35] Although the supramolecular chemistry of rhenium has evolved tremendously, the true potential of its congener manganese remains unrealized.…”

Neutral discrete metal–organic cyclic architectures: Opportunities for structural features and properties in confined spaces

“…Lu and co-workers [180] initiated the synthesis of a family of cyclometalated rhenium metallacycles, in which cyclometalating ligands have a beneficial effect on luminescence yields. A facile onepot synthesis of the dinuclear rhenium(I)-cyclometalated com-…”