Insight into the Heavy Atom Effect Induced by Environmental Heavy Atoms for Gadolinium-Labeled Hematoporphyrin Monomethyl Ether.

Environmental heavy atoms can further enhance the room temperature phosphorescence (RTP) emissions of gadolinium-labeled hematoporphyrin monomethyl ether (Gd-HMME) by way of the external heavy atom effect (HAE). However, the macroscopic phosphorescence intensity covered the intrinsic effect of the environmental heavy atoms. In this study, a method of separating the external HAE from the total is performed, and a quantity to describe the intrinsic nature of external HAE is defined. The environmental Gd concentration evolution of the phosphorescent transition rate () is obtained by correlated absorption, emission, and time-resolved spectroscopy. The increases linearly with environmental Gd concentration, while the intercept coincides with that of the internal HAE. The slope κ could be calculated, and it is a quantity free of the Gd concentration and only relies on the type of environmental heavy atoms. In addition, the environmental Lu exhibits similar functionality to Gd in external HAE. Environmental Pd quenches the phosphorescence intensity macroscopically, while it enhances the HAE intrinsically. Our method provides an alternative insight into the intrinsic nature of environmental heavy atoms.