Coexisting intraligand fluorescence and phosphorescence of hafnium(IV) and thorium(IV) porphyrin complexes in solution

The closed-shell metalloporphyrins Hf(TPP)(OAc)2 and Th(TPP)(acac)2 (TPP=dianion of tetraphenylporphyrin, OAc=acetate, acac=acetylacetonate) display intraligand fluorescence and additional heavy-atom-induced intraligand phosphorescence, which is observed at room temperature in fluid solution and very efficiently quenched by O2 with potential significance for the sensing of trace amounts of dioxygen.