Binuclear Gold(I) Complexes for Visible Light Photocatalysis
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Solution Overview
Problem
Current photoredox catalysis using d6 transition metal compounds like iridium(III) and ruthenium(II) is limited to outer-sphere electron transfer, unable to catalyze reactions requiring substrate binding or radical trapping, and gold(I) complexes like [Au2(μ-dppm)2] require high-energy UV light for photocatalysis, restricting their application in organic reactions.
Innovation Solution
Development of gold(I) complexes that absorb near-UV and visible light, enabling photocatalysis through substrate binding and radical trapping, with structures optimized for improved light absorption and reactivity in the visible spectral region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If d6 transition metal compounds (iridium(III) and ruthenium(II)) are used as photocatalysts, then photocatalysis under mild reaction conditions is achieved, but the catalysts are limited to outer-sphere electron transfer and cannot catalyze reactions requiring substrate binding or radical trapping
Solution Approach 1:
The patent changes the electronic configuration parameter from d6 to d10 by selecting gold(I) metals, which fundamentally alters the coordination geometry from octahedral to linear. This parameter change enables the catalyst to perform both outer-sphere electron transfer and inner-sphere substrate binding reactions, resolving the contradiction between mild reaction conditions and reaction versatility.
2Adaptability or versatility
If gold(I) complex [Au2(μ-dppm)2] is used as photocatalyst, then substrate binding and radical trapping are enabled, but high-energy UV light (365 nm) is required which poses difficulty in large scale synthesis
Solution Approach 1:
The patent modifies the ligand parameters (using N-heterocyclic carbene ligands with specific substituents) to alter the electronic structure and HOMO-LUMO gap of the gold(I) complex. This enables the complex to absorb lower energy visible light (400-450 nm) instead of high-energy UV light, while maintaining substrate binding capability through the linear coordination geometry enabled by d10 configuration.
3Illumination intensity
If gold(I) complex with high absorption coefficient is designed, then light absorption efficiency is improved, but the complex requires high-energy UV light which limits substrate scope
Solution Approach 1:
The patent changes the ligand substitution parameters (introducing electron-donating or electron-withdrawing groups at specific positions on the N-heterocyclic carbene ligands) to tune the HOMO-LUMO gap. This parameter optimization achieves high absorption coefficients in the visible region (400-450 nm) while maintaining the linear coordination geometry necessary for substrate binding, thus improving both light absorption efficiency and substrate scope simultaneously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These gold(I) complexes exhibit higher photocatalytic activity compared to traditional catalysts, allowing for efficient catalysis of reactions such as homocoupling, alkylation, cyclization, and C—H bond cleavage under mild conditions, with yields superior to existing catalysts like [Au2(μ-dppm)2], [Ru(bpy)3], and [fac-Ir(ppy)3].
Implementation Method 1
These gold (I) complexes can absorb light in the near-UV and/or visible regions
Implementation Method 2
Gold (I) complexes that can absorb light in the near-UV and/or visible regions and methods of making and using thereof are described. These gold (I) complexes have photochemical reactivities that allow them to catalyze photoredox reactions under near-UV and/or visible light.
Data Source
AI summary
Gold (I) complexes that can absorb light in the near-UV and/or visible regions and methods of making and using thereof are described. These gold (I) complexes have photochemical reactivities, such as strong absorption of near-UV and/or visible light, quenching rate constants ≥3.5×105 s−1, etc., that allow them to catalyze photoredox reactions, such as homocoupling of organic halides (e.g. alkyl halides and aryl halides), alkylation of 2-phenyl-1,2,3,4-tetrahydroisoquinoline, cyclization of indoles, reductive dehalogenation of aryl halides, and/or C—H bonds cleavage, under near-UV and/or visible light. The product of a photo-induced organic reaction catalyzed by the gold (I) complexes described herein can have a yield that is higher than the yield of the same product formed from the same reaction under the same reaction conditions, using the same loading or a higher loading of [Au2(μ-dppm)2](Cl)2, [Ru(bpy)3](Cl)2, and/or [fac-Ir(ppy)3] compared to the loading of the one or more gold (I) complex(es).