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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - BiMetaCat (Two Are Better Than One: Bimetallic Catalysts for the Conversion of Lignin-Derived Aryl-Ethers)

Teaser

Summary

Aromatic building blocks are essential for the production of pharmaceuticals, cosmetics and plastics but are mainly produced from finite fossil resources. Lignin, a complex biopolymer that is rich in aromatic rings, can serve as a renewable source for aromatic base chemicals. Significant advances towards the depolymerization of lignin now give access to a plethora of small aromatic compounds with a variety of valuable functional groups. However, current catalyst systems are unable to convert these compounds into aromatic building blocks without loss of these desirable functional groups. Hence, there is a need for the development of new catalysts that are capable of handling these oxygen-rich materials that are derived from biomass. Research towards new catalytic methodologies that allow valorization of highly oxygenated biomass-derived compounds is essential to decrease our dependence on fossil resources.

The objective of the proposed research was to design and synthesize new molecules that have two metal atoms in close proximity to each other, which can work together to make and break chemical bonds. The tunable nature of these molecules would allow to gain fundamental insights into what factors govern the activation of chemical bonds by two metal atoms. Specifically focusing on insights in the activation of the carbon oxygen bonds in lignin-derived aryl ethers could allow for the rational design of bimetallic catalysts for the conversion of lignin-derived compounds into valuable aromatic building blocks.

Work performed

\"In this project various routes toward novel molecules that can bind two metals in close proximity were investigated. This resulted in establishing reliable protocols that enable making these molecules on multigram scale. Subsequently, the binding of various metal atoms to these molecules was investigated, and it was found that two copper atoms can bind in close proximity to each other. The reactivity and electronic structure of these dicopper complexes was studied in great detail and it was found that both the metals and the ligands can work together to make and break chemical bonds, thereby mimicking a concept that is found in nature. In addition, it was found that these molecules can undergo subtle modifications by treating them with acid or base, and that these changes drastically affect the way the two copper atoms behave. Unfortunately, the dicopper complexes that were made thus far are unreactive towards lignin-derived compounds. Nonetheless, various important protocols, strategies and ideas were obtained during this project, which has laid the foundation for future research projects aimed at the use of bimetallic complexes for sustainable chemical conversions.

The following key results were discovered during the project:
- the establishment of four reliable synthetic routes towards tunable molecules that can bind two metal atoms in close proximity
- The synthesis and characterization of various complexes where two copper atoms are bound in close proximity
- The discovery of unprecedented chemical reactivity enabled by the molecular design of the dicopper complexes
- Valuable insights into which metal atoms can be bound in close proximity in the newly made molecules, and how certain parameters affect the reactivity of the corresponding dicopper complexes.

Dissemination:
The findings of the work performed in this project were very well received by the community working in this specific (and related) fields of research. The findings have been reported in two scientific publications (open access) in high-quality peer reviewed journals: \"\"Chemistry - A European Journal\"\" and \"\"Organometallics\"\". Moreover, these exciting and other unusual findings were communicated on LinkedIN, Twitter (@BroereDaniel) and www.broerelab.com. The findings of this project were also presented in poster presentations at two international conferences: CHAINS 2019, NL and at the 20th IUPAC International Symposium on Organometallic Chemistry Directed Towards Organic Synthesis, DE. Two oral presentations were also given at the international conferences: CHAINS 2019, NL and the 21st Netherlands\' Catalysis and Chemistry Conference Noordwijkerhout, NL. In addition, the work was presented as part of invited lectures at various Dutch universities and at national meetings (The Debye Chemistry day 2019 and NextGenChem 2019). Finally, a a professional short film (www.eye-openers.nl) was recently recorded wherein the research is explained in laymanâ€™s terms. The production of the video is currently ongoing.\"

Final results

\"We have developed new molecules that can bind two metal atoms in close proximity unlike any other previously reported system. Moreover, these systems were shown to make and break chemical bonds in an unprecedented way. Both these key findings have no direct socio-ecomonomic impact or wider societal implications thus far but present a key contribution to the field of \"\"bimetallic catalysis\"\" and its applications in the utilization of chemical building blocks derived from biomass waste. Further work is needed to investigate the potential in this regard.\"