Research Activity

The early scientific interests of Dante Gatteschi were focussed on the use of ligand field theory for the description of the electronic structure and of the spectral and magnetic properties of low symmetry transition metal compounds. Among the most interesting results the development of suitable models for the electronic levels of five coordinate transition metal compounds, a hot topic at that time, and a battle horse of the florentine school. The need to investigate copper(II) compounds undergoing Jahn-Teller distortions pushed him to use EPR spectroscopy as a strong tool for the understanding of the static and dynamic structures of transition metal ions. Many papers have been devoted to the correlation between spin hamiltonian parameters of the EPR spectra and electronic structure of the metal ions. For instance a systematic investigation of the EPR spectra of high spin cobalt(II), a difficult ion for EPR because very low temperatures are needed to observe the spectra, provided for the first time a clear understanding which opened the way to the interpretation of the spectra in biological systems.

The natural extension of these investigations was towards systems in which metal ions are magnetically coupled, first in pairs, and later in more and more complex structures. Again the use of EPR in this area has been very extensive, and some important results were summarized in the book coauthored with Alessandro Bencini on “EPR of Exchange Coupled Systems”, which is largely referenced by people active in the field. Particular attention was devoted to mixed valence pairs: the system with two nickel ions (Ni^II-Ni^I) bridged by naphthiridine ligands is still a classic example of strong delocalization.

Molecular magnetism is the current interest, both as the design and synthesis of molecular based magnetic materials and as the investigation of single-molecule magnets. In the former field the original approach was that of using metal ions directly bound to stable organic radicals, like nitronyl nitroxides and semiquinones. Molecular ferrimagnets with critical temperatures up to 25 K have been synthesized, and their magnetic properties investigated with a large number of different techniques, ranging from magnetization to neutron diffraction and scattering. In fact it is one of the features of the Gatteschi’s group that of using many different physical techniques and going deep in the physical characterization of the materials. This is particularly clear in the last investigations on the single molecule magnets, which were discovered in Florence, and which are currently in the forefront of intensive interdisciplinary research, aiming at the investigation of molecular bistability and of quantum tunneling of the magnetization.