One of the current challenges in the chemical industry is to find methods that facilitate the optimisation of catalysts capable of enabling the development of new chemical processes. Catalyst optimisation is usually based on trial-and-error testing, in which the properties of the catalyst are improved through a slow and routine process aimed at identifying the best combinations of ligand and metal, which are its basic components. Once the catalyst has been optimised, its properties are fixed and adapted to the specific requirements of a particular chemical process.
A highly interesting alternative to this method is to design a catalyst that contains a ligand whose properties can be modulated through the application of an external stimulus. These properties, known as "switchable", are much easier to modulate and therefore to adapt to the specific needs of each reaction. Over the past four years, the Organometallic Chemistry and Homogeneous Catalysis Group (QOMCAT) at the Universitat Jaume I has designed a series of multisensitive catalysts capable of adapting their properties through the application of electrochemical, light-based, chemical and supramolecular stimuli.
Adapting the properties of a catalyst through an external stimulus greatly simplifies the optimisation process and enables a single catalyst to be used to facilitate a wide range of chemical transformations. The QOMCAT group's strategy has been to synthesise ligands that combine naphthalene diimides (NDIs) with N-heterocyclic carbenes (NHCs). NDIs are organic compounds that are highly sensitive to multiple stimuli, such as electrochemical or light-based stimuli, and even to the addition of anions or supramolecular additives. NHC ligands, in turn, offer great coordination versatility and structural diversity, enabling the synthesis of a large variety of metal-based catalysts with remarkable geometric versatility.
The group's second line of research falls within what is known as supramolecular chemistry. Supramolecular chemistry is the branch of chemistry that studies supramolecular interactions—interactions between molecules—which helps us understand the biological world and establish the principles of nanotechnology. This line of research has led QOMCAT to obtain highly relevant results with significant impact and international recognition.
In 2022, the group obtained a new type of "mechanically interlocked molecule" (MIM), consisting of two interlocked acyclic molecules. This molecule, named clipane, introduces a new paradigm within the MIMs known to date (catenanes and rotaxanes), since the type of mechanical bond established between its components is highly novel. The results, featured in numerous science communication journals, including the prestigious journal Science, represent a further step forward in the design of molecular machines and open the door to the development of new materials with properties yet to be discovered.
QOMCAT has also studied dynamic systems in which a molecule confined within the cavity of a larger one undergoes controlled motion. Understanding the factors that determine the movement of the confined molecule (guest) within the molecule containing the cavity (host) is essential for designing systems in which such movements can be promoted in a targeted way and, therefore, used in the design of molecular machines.
In 2024, the group designed a "molecular shuttle" in which a molecule confined within the cavity of a nanometre-sized host exhibited translational motion whose speed could be controlled by temperature. This result represents a major breakthrough in the design of molecular machines and attracted considerable scientific attention. In the poll organised by C&EN News to select the most significant molecule of the year, the molecular shuttle ranked second, just after the cyclodextrin developed by Nobel laureate Sir Fraser Stoddart, and the same publication—one of the most prestigious chemistry outreach journals—also published an article about this achievement.
This research is part of project PID2021-127862NB-I00, funded by MICIU/AEI/10.13039/501100011033 and FEDER/EU under the 2021–2023 State Plan for Scientific, Technical and Innovation Research, as well as projects funded by the Generalitat Valenciana (CIPROM/2021/079), the Universitat Jaume I (UJI-B2020-01) and TED2021-130647B-I00.
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