Design of luminescent lanthanide complexes: From molecules to highly efficient photo-emitting materials

Abstract The incorporation of luminescent lanthanide complexes in solid matrices with controlled structural organization is of widespread interest in materials science and has witnessed important improvements with the development of low-temperature soft chemistry solution processes, such as sol–gel. In this review, after an introductory part concerning some relevant aspects of the electronic and coordination properties of lanthanides, the prominent issues related to the design and synthesis of efficient luminescent antenna complexes, and their photophysical properties are presented. We describe the basic principles of ligands design to yield systems featuring a coordination site for the metal cation with appended suitable chromophores as sensitizers (two-component approach). When properly designed, these ligands are capable of forming highly luminescent complexes (overall sensitization yield, ϕ se  > 0.05 in aqueous medium). The photophysical properties of these complexes together with the description of some emitting materials prepared are discussed in detail. In particular we focus the attention toward those complexes emitting in the visible region that can be used in the lighting industry (e.g. for the preparation of photo- and electro-luminescent materials) and for biological immunoassays. Subsequently, some selected results of our recent work concerning the synthesis of highly luminescent colour tunable films for applications in lighting and light conversion technologies are reported. Such materials have been obtained by combining the peculiar luminescence properties of Eu 3+ and Tb 3+ antenna complexes with optically transparent inorganic matrices. The notion is to create materials with innovative properties by integrating inorganic and organic components at nanoscale or molecular level. Due to the number of scientific publications in this field, this work is far from providing an exhaustive review on the previously performed research activities. For a more detailed discussion on these methodologies, the reader can refer to specific pertinent literature.