Effect of Paramagnetic Open-Shell Gadolinium(III) Texaphyrin on Its Kinetics and Electronic Structures in Fluorescence and Phosphorescence Emission States

Abstract

The paramagnetic effect, which was often found to quench the fluorescence and decrease the phosphorescence radiative lifetime, has not been quantitatively studied for gadolinium­(III) complexes that do not have low-lying 4f orbitals. Meanwhile, much attention also needs to be paid to distinguish the paramagnetic effect with the heavy-atom effect, both of which are believed to display a very similar influence on the kinetics of fluorescence and phosphorescence. In this work, a detailed theoretical investigation of the paramagnetic effect observed in earlier experiments for the open-shell gadolinium­(III) texaphyrin (Gd-Tex) is given by the time-dependent density functional theory with the 4f-in-valence lanthanide pseudopotential. The results show that the paramagnetic effect is realized by the interaction between Gd­(III) 4f and ligand σ excited electrons bridged by the Gd­(III) 6s orbital, and the electronic structure of the ligand-centered fluorescence emission state is mixed with the metal-centered ones, which significantly affects the fluorescence quenching mechanism. No such hybrid state is observed in the Gd-Tex phosphorescence spectrum, indicating that the heavy-atom effect should be to blame for the much shorter radiative lifetime of phosphorescence in the paramagnet. The findings in this work help to rationalize the existing experimental data and to promote the potential therapeutic usage of texaphyrins as photosensitizers in the photodynamic therapy.

Balancing the phosphorescence and fluorescence of a double-ring porphyrin using different lanthanides for ratiometric oxygen sensing

“…25 Paramagnetism has also been reported to induce state mixing. 26,27 The phosphorescence observed for the DVDMS complexes in this study is related to both the HAE and paramagnetism. Gadolinium( iii ) is strongly paramagnetic because it has seven uncoupled electrons.…”

Lutetium-containing sinoporphyrin sodium: a water-soluble photosensitizer with balanced fluorescence and phosphorescence for ratiometric oxygen sensing

“…Paramagnetism has also been reported to mix states. [38][39][40] The phosphorescence-inducing effect dened in this work is related to both HAE and paramagnetism. As reported by Wang et al, 5 the relatively strong RTP of Gd-porphyrin results from the special energy levels, strong paramagnetism, and HAE of Gd(III).…”

“…Details of the measurement are given in Fig. S3 induce a larger extent of mixing between the singlet and triplet states 36 of DVDMS than Lu(III). Thus, Lu-DVDMS has a lower quantum yield of triplet state formation than Gd-DVDMS, and its singlet-oxygen quantum yield is lower than that of Gd-DVDMS.…”

Universal “Three-in-One” Matrix to Maximize Reactive Oxygen Species Generation from Food and Drug Administration-Approved Photosensitizers for Photodynamic Inactivation of Biofilms

“…Guided by the Jablonski diagram, here we proposed a universal matrix to maximize ROS generation from classical PSs (especially FDA-approved PSs), resulting in a significantly improved triplet quantum yield (Φ T , 1.5-fold) and ROS generation (1.5–9.0-fold). Specifically, the coordination nanoparticles (CNs) from self-assembled Gd 3+ and purine nucleotides (Figure S1) were explored for facile encapsulation of PSs, − in which the coordination networks efficiently fixed PSs and inhibited the non-radiative transitions (process ① in Figure a), while Gd 3+ further propelled the energy flux of S 1 → T 1 through heavy atom ( Z = 64, process ② in Figure a) and paramagnetic (4f 7 ) effects (process ③ in Figure a), , namely, a “three-in-one” matrix for ROS boosting (Figure a). The coordination networks could flexibly fit the shape of guest molecules, resulting in a universal matrix for a broad band of classical PSs (e.g., porphyrin, porphine, indocyanine, AIE, and benzothiazole-based PSs).…”