Activataion of Soft Molecules directed toward Intelligent Materials (Soft Molecular Activation (SMA))
Catalysts developed from soft iodine, graphene and metal complexes could transform smart material technologies
The very idea of materials that change their shape or function as required sparks the imagination. Smart materials are impressive artificial molecules, often inspired by naturally occurring chemicals, which have the potential to revolutionize design. They undergo changes that are reversible and repeatable, meaning they can function as molecular switches, valves and sensors. Other smart materials include shape-memory alloys that return to their original shape after bending, metal-bearing polymers that can switch from insulator to conductor and drug-delivery systems that slowly release pharmaceuticals where and when they are needed.
Researchers at the Soft Molecular Activation for Intelligent Materials program are leading investigations into catalysts made from soft molecules that could one day transform smart material design.
Lead researcher Takayoshi Arai says the program is focused on developing powerful catalysts to create novel smart materials using three catalyst types. “Firstly, soft halogen catalysts, predominantly using iodine, can be used to develop highly targeted medications,” he explains. “A second type is ‘soft -electron’ using carbon nanotubes and graphene, which would provide a unique reaction sphere for catalysis. The third type, ‘soft metal’ catalysts allow us to introduce soft elements such as gold and copper into target molecules.”
New catalyst design
Arai says one of the main goals is to create new asymmetric catalysts, which are used to generate large numbers of very specific molecules. Most biological molecules are chiral, meaning they exist in one of two mirror-image forms called enantiomers. Many drugs and smart materials use just one specific enantiomer, and so catalysts are needed to direct the chemical reactions toward forming the correct enantiomer.
For example, iodine has been used to help synthesize specific enantiomers of cyclic and ring-shaped molecules. “We are lucky that Chiba prefecture in Japan is one of the world’s leading producers of iodine,” says Arai. “In fact, the Chiba Iodine Resource Innovation Center (CIRIC) will open at Chiba University next year. For this reason, a key goal of our program is to perfect iodine-based soft molecular activation.”
Recent success for Arai’s team includes the development of an aminoiminophenoxy-copper carboxylate catalyst that can trigger high yields of O-cyclized molecules. These can, in turn, be used to generate a particular chiral compound that is invaluable for use in antimicrobial and antiosteoporotic compounds.
“A crucial part of our research is designing catalysts that can be reused multiple times, thereby creating cost-effective, sustainable methods for generating useful compounds,” says Arai. His team recently designed a recyclable catalyst made from a zinc-polymeric ligand complex. The polymeric ligand allows the catalyst to be separated from the final product by a simple filtration process, meaning it can be reused — indeed, poly-Zn remained a stable and active catalyst for creating iodine-based ring-shaped molecules more than five times.
“By introducing soft elements to target molecules, our research will facilitate the development of smart materials with smooth and rapid responses,” says Arai. “We welcome anyone interested in research at the forefront of iodine-related soft molecular activation chemistry to come and work in this diverse and challenging field at Chiba.”