Very proud to see my first last-author paper published!
We report dramatic effects of a ligand backbone modification on 3MLCT lifetimes in Cr/Mo/W complexes. Read how we disentangle potential energy well flattening, conformations and self-quenching below!
@labheinze.bsky.social
We recently reported a molecular design for carbonylpyridine molybdenum(0) complexes that unlocks long-lived luminescent and photoactive charge-transfer states. Here, we translate this strategy to chromium(0), and tungsten(0) and report three fully characterized tricarbonyl metal(0) complexes featuring a tripodal ligand with a remote n-butyl substituent in the backbone. All complexes show phosphorescence in the red to near-infrared spectral region from metal-to-ligand charge-transfer excited states. Surprisingly, the alkyl chain significantly affects excited state relaxation: lifetimes are shortened in solution but extended in the solid state by one order of magnitude compared to the molybdenum(0) complex with a methyl substituent. Temperature-dependent luminescence and NMR spectroscopy in combination with quantum chemical calculations reveal the reasons for these disparate effects. The n-butyl substituent distorts the metal coordination geometry. The resulting structural flexibility flattens the potential energy surfaces in solution, which lowers the barrier for the population of distorted metal-centered states and facilitates nonradiative relaxation. In the solid state, the rigidified alkyl chain separates neighboring molecules, which reduces self-quenching. Our study sheds light on the relationship between structure and excited state relaxation to inform the development of photoactive complexes based on earth-abundant metals.
A Blessing and a Curse: Remote Ligand Functionalization Modulates 3MLCT Relaxation in Group 6 Tricarbonyl Complexes pubs.acs.org/doi/10.1021/... @winald_kitzmann @LabHeinze and co-workers @InorgChem #chromium #molybdenum #tungsten #carbonylpyridine #3MLCT #flattening #spacer
