The benefit of switching to red light can be substantial, if you can still do your transformation with lower energy than you might be accustomed to in the near UV and blue region. And while we\u2019re not a fan of the consequences when things shift from Blue to Red, in photochemistry the results can be advantageous. Red light can offer deeper penetration in certain media (such as skin or some polymers) has a higher percentage in sunlight (if you\u2019re into the potential of that sort of thing), is safer and lower in energy. In several instances a switch to lower energy red light helped to eliminate unwanted photodegradation side products.<\/p>\n
In their present work \u201cSynthesis, Characterization, and Catalytic Activity of Ni(0) (DQ)dtbbpy, an Air-Stable, Bifunctional Red-Light-Sensitive Precatalyst<\/a>\u201d published recently in JACS<\/em>, Dong Xue and coworkers at Shaanxi Normal University bring nickel photocatalysis into the red, specifically nickel(0) catalysis. Nickel catalysts are quite familiar in photochemistry as numerous examples exist combining nickel and iridium catalysts with blue LEDs (see in any chemistry journal from 2016 to 2025) or on their own like one of our favorite papers by Miyake and coworkers<\/a> for cross coupling chemistry, usually with something purple (365 nm). But to find a nickel catalyst suitable for work in the red region, first the authors needed to make a new catalyst.<\/p>\n Figure 1:<\/strong> Synthesis of Ni(0)(DQ)dtbbpy<\/p>\n Nickel(0) catalysts are well known in thermal catalysis; however, to date a nickel(0) precatalyst has not been known for photocatalysis. And so, the authors first looked to make their new catalyst. Starting from Ni(COD)DQ with dtbbpy, the authors prepared Ni(0)(DQ)dtbbpy in one step in 84% yield (Figure 1). They fully characterized their new catalyst including UV spectroscopy, CV and X-Ray crystallization. The new catalyst is air stable for several days, demonstrates an absorption band at 565 nm and can undergo 1 or 2 electron processes.<\/p>\n This new Ni(0) complex catalyzes reactions that could not be performed with the original Ni(COD)DQ or other Ni(0) catalysts. The initial test reaction for Ni(0)(DQ)dtbbpy involved the C-O coupling of bromobenzene and n<\/em>-butanol. Utilizing toluene, red light and a base (DMTHPY) with some heating to 80 \u00b0C gave conversion at 75% (Figure 2). Switching out the nickel catalyst gave no reaction as did removing the base. Heating the catalyst to 85 \u00b0C in an oven for 4 hours prior to use gave no difference in reaction showing the stability of the catalyst, while storing the catalyst for 5 days in air showed minimal detrimental effects. However, lowering the temperature to 60 \u00b0C gave no reaction while the reaction without light but heating at 80 \u00b0C gave 10% conversion. The presence of air lowered the conversion to 58%.<\/p>\n Figure 2:<\/strong> Optimizing Reaction condition<\/p>\n The optimized condition was applied to various meta<\/em> and para<\/em> substituted aryl bromides including acetyl, cyano, halogen, tert<\/em>-butyl and trifluoromethyl groups and was extended to heterocyclic systems as well. The reaction was successful for a variety of alcohols and extended to C-N coupling with a variety of amines. Switching to red light afforded a few key advantages, mainly low dehalogenation of substrates, low absorption of light by other reagents and limited nickel black formation. Overall, this system afforded gram scale synthesis. Further mechanistic studies and DFT analysis investigated factors associated with the photochemical and thermal aspects of the catalytic cycle showing the role both play in this catalytic cycle.<\/p>\n This work further demonstrates that there is more to photochemical life than blue and purple. Finding the right combination of catalyst, wavelength and reaction media can find the ideal use for an application. At scale, consider the cost difference between a reaction with an expensive iridium catalyst and blue LEDs verses cheap nickel and potentially sunlight. Overall, a nice move in the direction of increasing the flexibility of Ni photochemistry. Now, lets work on that operating temperature for this system\u2026.<\/p>\n [\/et_pb_text][\/et_pb_column][\/et_pb_row][\/et_pb_section]<\/p>\n","protected":false},"excerpt":{"rendered":" Discover the power of red light in photochemistry! Explore recent advances in red LED-driven synthesis, from C-N coupling – protein labeling.<\/p>\n","protected":false},"author":7786,"featured_media":24763,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"on","_et_pb_old_content":"We are huge fans of what could be classified as \u201ccreative photocatalysts\u201d. One of our favorite papers over the past few years was this work that we wrote about here<\/a> using Hypericum flowers as an organic dye for C-C bond formation. A few dried flower petals, a base and an LED and you have a new photochemical reaction. So, if your paper can be described as using a \u201cFenton Boat photocatalyst\u201d, well you have our attention.\r\nIf you Google \u201cFenton Boats\u201d, you get links to a boat shop in Fenton, Michigan, but we\u2019ll argue that soon you will get this recent paper in Angewandte from Zhijun Chen and coworkers entitled, \u201cA Sustainable Wood-Based Iron Photocatalyst for Multiple Uses with Sunlight: Water Treatment and Radical Photopolymerization<\/a>\u201d\r\nWhat\u2019s a Fenton Boat? Stick around and we\u2019ll explain. And show you a video of a photocatalyst boat.\r\n\r\nEmbed tweet:\r\n A Sustainable Wood-Based Iron Photocatalyst for Multiple Uses with Sunlight: Water Treatment and Radical Photopolymerization (Zhijun Chen and co-workers) https:\/\/t.co\/ayHH23uBwY<\/a> pic.twitter.com\/m4a8kJ0jet<\/a><\/p>\u2014 Angewandte Chemie (@angew_chem) May 2, 2023<\/a><\/blockquote> ![\"red](\"https:\/\/hepatochem.com\/wp-content\/uploads\/2025\/03\/Figure-1-1024x344.jpg\")
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