Sinha N, Wenger OS. Photoactive Metal-to-Ligand Charge Transfer Excited States in 3d
6 Complexes with Cr
0, Mn
I, Fe
II, and Co
III.
J Am Chem Soc 2023;
145:4903-4920. [PMID:
36808978 PMCID:
PMC9999427 DOI:
10.1021/jacs.2c13432]
[Citation(s) in RCA: 40] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Many coordination complexes and organometallic compounds with the 4d6 and 5d6 valence electron configurations have outstanding photophysical and photochemical properties, which stem from metal-to-ligand charge transfer (MLCT) excited states. This substance class makes extensive use of the most precious and least abundant metal elements, and consequently there has been a long-standing interest in first-row transition metal compounds with photoactive MLCT states. Semiprecious copper(I) with its completely filled 3d subshell is a relatively straightforward and well explored case, but in 3d6 complexes the partially filled d-orbitals lead to energetically low-lying metal-centered (MC) states that can cause undesirably fast MLCT excited state deactivation. Herein, we discuss recent advances made with isoelectronic Cr0, MnI, FeII, and CoIII compounds, for which long-lived MLCT states have become accessible over the past five years. Furthermore, we discuss possible future developments in the search for new first-row transition metal complexes with partially filled 3d subshells and photoactive MLCT states for next-generation applications in photophysics and photochemistry.
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