Microsecond Photoluminescence and Photoreactivity of a Metal-Centered Excited State in a Hexacarbene-Co(III) Complex

Simon Kaufhold; Nils W Rosemann; Pavel Chábera; Linnea Lindh; Iria Bolaño Losada; Jens Uhlig; Torbjörn Pascher; Daniel Strand; Kenneth Wärnmark; Arkady Yartsev; Petter Persson

doi:10.1021/jacs.0c12151

Microsecond Photoluminescence and Photoreactivity of a Metal-Centered Excited State in a Hexacarbene-Co(III) Complex

J Am Chem Soc. 2021 Jan 27;143(3):1307-1312. doi: 10.1021/jacs.0c12151. Epub 2021 Jan 15.

Authors

Simon Kaufhold^{1

2}, Nils W Rosemann^{1

2}, Pavel Chábera², Linnea Lindh^{2

3}, Iria Bolaño Losada³, Jens Uhlig², Torbjörn Pascher⁴, Daniel Strand¹, Kenneth Wärnmark¹, Arkady Yartsev², Petter Persson³

Affiliations

¹ Center for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden.
² Division of Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden.
³ Division of Theoretical Chemistry, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden.
⁴ Pascher Instruments AB, Stora Råby Byaväg 24, S-22480 Lund, Sweden.

Abstract

The photofunctionality of the cobalt-hexacarbene complex [Co(III)(PhB(MeIm)₃)₂]⁺ (PhB(MeIm)₃ = tris(3-methylimidazolin-2-ylidene)(phenyl)borate) has been investigated by time-resolved optical spectroscopy. The complex displays a weak (Φ ∼ 10^-4) but remarkably long-lived (τ ∼ 1 μs) orange photoluminescence at 690 nm in solution at room temperature following excitation with wavelengths shorter than 350 nm. The strongly red-shifted emission is assigned from the spectroscopic evidence and quantum chemical calculations as a rare case of luminescence from a metal-centered state in a 3d⁶ complex. Singlet oxygen quenching supports the assignment of the emitting state as a triplet metal-centered state and underlines its capability of driving excitation energy transfer processes.