Tailoring Photoactive Metal Complexes: Design, Catalysis and Chirality

Tailoring Photoactive Metal Complexes: Design, Catalysis and Chirality

Dr. Winald Kitzmann
Massachusetts Institute of Technology, Cambridge, MA, USA

Complexes based on precious or rare-earth metals show beautiful optical properties, but their high cost limits large-scale applications.^[1] This talk explores complexes based on earth-abundant metal complexes in different oxidation states as cheap alternatives, covering their molecular design, fundamental photophysical properties and performance in potential applications.

In the first part, I present a new design strategy to obtain low-cost Cr⁰, Mo⁰ and W⁰ carbonyl complexes with long-lived excited states. The complexes shows red ³MLCT emission reminiscent of [Os(bpy)₃]²⁺ with excited state lifetimes up to several 100 ns and a very high photostability. I will discuss the intrinsic reasons for these remarkable properties and show the versatility of the Mo⁰ complex in green-to-blue photon-upconversion and photoredox catalysis.^[2]

The second part deals with spin-flip emitters with photoactive metal-centered states. First, I will lay out the fundamentals of spin-flip emission using the well-established Cr^III based molecular rubies with bright NIR phosphorescence.^[3] Then I will show the dramatic effects on the excited states when replacing Cr^III with Mo^III that I found in my work.^[4]

The last part of this talk explores chiral Cr^III complexes and their circularly polarized luminescence (CPL) with perspectives for energy-efficient displays, high-contrast microscopy and quantum technology. As accurate CPL measurements are critical for this rapidly growing field, I will share learnings from my home-built spectrometer and which pitfalls to avoid.^[5]