Recent developments on luminescent octahedral transition metal cluster complexes towards biological applications

Abstract

The luminescent octahedral molybdenum, tungsten, and rhenium cluster complexes have attracted a broad interest in the past decades for the design of photofunctional materials. These complexes, with the general formula [{M6Li8}La6]n, display red phosphorescence with high quantum yields, quenching of their emission by oxygen, and robust production of singlet oxygen, O2(1Δg). In addition, the wide range of inner (Li) and apical (La) ligands allows for a fine tuning of their physico-chemical, photophysical, and biological properties and for additional functionalization with regards to targeted applications. In this review, we summarize the recent developments towards the use of these complexes for biological applications such as photodynamic therapy, computed tomography, or photoinactivation of bacteria. The synthetic methods and properties of these complexes are presented and we encompass the different approaches towards photo-related biological applications through standalone use of these complexes or by their incorporation into (nano)materials. We identify the key parameters and the challenges for successful biological application of this class of transition metal cluster complexes.