Eugenio Coronado talks to Gavin Armstrong about the molecular design of magnetic materials and current challenges in the field.

	Eugenio Coronado is professor of inorganic chemistry at the University of Valencia, Spain, and is director of the university's institute of molecular science. His interests lie in the area of molecular magnetism, particularly in the design and study of multifunctional magnetic materials and molecular nanomagnets.

What attracted you to chemistry?
I have always been interested in science but chemistry allowed me to use a lot of creativity; chemists should create compounds that they or other scientists study. Chemistry also contains a lot of physical principles. This combination of chemical creativity with solid state physics allows me construct interesting new systems.

What led you into magnetic materials?
In the field of coordination chemistry, I found magnetic materials the most interesting systems to study because they are at the interface between chemistry and physics. Chemists have been interested in the magnetism of materials for years, but we need a great understanding of physics to improve their properties. In this context, the molecular approach has been an excellent tool to design novel magnetic materials with the desired properties, and to create ideal magnetic models to check the theories, or even to develop novel theories. For example, in the 1980's, we studied extended one-dimensional ferrimagnetic systems. At that time, low dimensional materials were an interesting topic for physicists, but chemists were the ones who designed novel classes of such materials. Chemistry can be used to solve and motivate some physical problems and vice versa.

What types of magnetic systems are you working on?
There are several kinds of materials that I find interesting. Magnetic solids based on molecules are one type but they cannot be processed easily. In most cases, you cannot dissolve them as they are coordination polymers. Currently, we are trying to make these crystalline solids easier to work with. If you can solubilise them, this will allow you to use nanotechnology, for example soft lithography, to print the materials onto a surface and thus generate organised magnetic nanostructures. This 'top-down' approach allows you to fabricate nanosystems from crystals.

The other possibility is to start from molecules and functionalise them to make them suitable for creating a nanostructure. This is the 'bottom-up' approach. Organising these molecules in one, two or three dimensions is a challenge because it cannot be fully controlled. They can self-assemble spontaneously to give rise to a certain organisation. However, there is a relationship between the functionalisation of the molecules and the structure of the final materials you obtain, so if you design your system well, you can get the system you want.

You can also impose organisation on a molecular system, playing, for example, with the nature of the surface on which the molecules are deposited. The supramolecular interactions of the molecules that dictate the self-assembly are now not the only important ones - you also have the interactions with the surface. We are just starting out with these systems. They are not very well known and that attracted me to work in this area.

You are interested in multifunctional materials. Could you explain a little about these types of materials?

Developing multifunctional materials is a big challenge in materials science and to obtain them by design is not easy. We are trying to design materials that show ferromagnetism and superconductivity and investigate the new physics behind this type of combination, which very few systems display. To reach this goal we are combining the appropriate molecular building blocks in solution to obtain a layered hybrid solid formed by an organic conductor and an inorganic magnet.

We are also developing switchable magnetic materials. Materials in which, for example, you apply pressure, light or a change in temperature and the material changes its magnetic behaviour. This unique possibility, provided by the molecular chemistry, is very promising in view of the potential applications of these materials in molecular electronics or spintronics.

We are always trying to see what the advantages of our molecular magnetic materials are compared to the classical ones. One advantage is the way we prepare them because we can take advantage of the molecular chemistry to design, for example, materials with combination of properties that are difficult or impossible to obtain using solid-state approaches. We also work at room temperature so the materials are cheap to prepare.

What is the biggest challenge facing molecular magnetic chemistry?

The biggest challenge is developing systems that are useful at high temperature; above 80 Kelvin using liquid nitrogen would be useful, but, obviously, above room temperature would be better and cheaper. Currently, our materials' properties are good but only at low temperatures, from 4 to 20 Kelvin.

A challenge that I expect to be solved within the next few years is measuring the magnetic properties of one single molecule. We can measure the magnetism of nanoparticles but these are 1000 metal atoms in size. For molecular nanomagnets, we are talking about 10 atoms.

What is the secret to being a successful scientist?
A scientist must look around the edges of what they are doing to avoid losing many important discoveries along the way. It is important to focus your activity in the boundary between different fields. The evolution of other fields around you may inspire your research and, with your expertise, you can contribute to the development of these fields.

What would you be if you weren't a scientist?

An artist. I debated whether to become an artist or a scientist but if you are not an excellent painter and a genius of creativity, it is very difficult to succeed to a good level. Being a scientist is more of an intellectual activity, but artistic creativity is also essential and certainly contributes to scientific success.