Light Activation and Photophysics of a Structurally Constrained Nickel(II)-Bipyridine Aryl Halide Complex

0583883 - ÚOCHB 2025 RIV US eng J - Journal Article
Bím, Daniel - Luedecke, K. M. - Cagan, D. A. - Hadt, R. G.
Light Activation and Photophysics of a Structurally Constrained Nickel(II)-Bipyridine Aryl Halide Complex.
Inorganic Chemistry. Roč. 63, č. 9 (2024), s. 4120-4131. ISSN 0020-1669. E-ISSN 1520-510X
EU Projects: European Commission(XE) 883987 - PhotoRedOx
Research Infrastructure: e-INFRA CZ II - 90254
Institutional support: RVO:61388963
Keywords : excited-state * photoredox catalysis * oxidative addition
OECD category: Inorganic and nuclear chemistry
Impact factor: 4.6, year: 2022
Method of publishing: Limited access
https://doi.org/10.1021/acs.inorgchem.3c03822

Transition-metal photoredox catalysis has transformed organic synthesis by harnessing light to construct complex molecules. Nickel(II)-bipyridine (bpy) aryl halide complexes are a significant class of cross-coupling catalysts that can be activated via direct light excitation. This study investigates the effects of molecular structure on the photophysics of these catalysts by considering an underexplored, structurally constrained Ni(II)-bpy aryl halide complex in which the aryl and bpy ligands are covalently tethered alongside traditional unconstrained complexes. Intriguingly, the tethered complex is photochemically stable but features a reversible Ni(II)-C(aryl)><- [Ni(I)<middle dot><middle dot><middle dot>C(aryl)(center dot)] equilibrium upon direct photoexcitation. When an electrophile is introduced during photoirradiation, we demonstrate a preference for photodissociation over recombination, rendering the parent Ni(II) complex a stable source of a reactive Ni(I) intermediate. Here, we characterize the reversible photochemical behavior of the tethered complex by kinetic analyses, quantum chemical calculations, and ultrafast transient absorption spectroscopy. Comparison to the previously characterized Ni(II)-bpy aryl halide complex indicates that the structural constraints considered here dramatically influence the excited state relaxation pathway and provide insight into the characteristics of excited-state Ni(II)-C bond homolysis and aryl radical reassociation dynamics. This study enriches the understanding of molecular structure effects in photoredox catalysis and offers new possibilities for designing customized photoactive catalysts for precise organic synthesis.
Permanent Link: https://hdl.handle.net/11104/0351874