A manganese(I) complex with a 190 ns metal-to-ligand charge transfer lifetime
Sandra Kronenberger1, Robert Naumann1, Christoph Förster1
1Department of Chemistry, Johannes Gutenberg University Mainz, Mainz, Germany.
Abstract:
Application of photoactive transition metal complexes in lighting, imaging, sensing, and photocatalysis is usually based on the triplet metal-to-ligand charge transfer (3MLCT) excited state of precious metal complexes with 4/5d6 valence electron configurations. These photocatalysts exhibit excited state lifetimes exceeding hundreds of nanoseconds. Simple 3d6 transition metal complexes containing abundant metals exhibit lifetimes below 1-2 nanoseconds, and they require multistep ligand syntheses mitigating large-scale implementation. We report that a commercially available bis(imidazolium) pyridine pro-ligand [H2pbmi]2+ and a manganese(II) salt yield the tetracarbene manganese(I) complex [Mn(pbmi)2]+. This complex phosphoresces at room temperature in fluid solution from a 3MLCT state with a lifetime of 190 ns. In combination with the reversible [Mn(pbmi)2]2+/+ process, this translates to an excited state capable of reducing benzophenone. Combination of manganese(I) with rigid carbene/pyridine ligands expands key strategies for photoactive 3d6 metal complexes of earth-abundant metals with 3MLCT lifetimes rivalling those of precious metals and providing a conceptual starting point for a sustainable photochemistry.
Related Concept Videos
02:51Metal-Ligand Bonds
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
01:19Complexation Equilibria: The Chelate Effect
01:09Complexation Equilibria: Factors Influencing Stability of Complexes
03:45Formation of Complex Ions
01:07Ladder Diagrams: Complexation Equilibria
The formation constant, K1, for the formation of Cd(NH3)2+ complex from cadmium and ammonia is 3.55 × 102. Log K1 (i.e. pNH3) is 2.55, and...
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...