Synthesis and Spectroscopic Investigation of Sensitized Near-Infrared Emission of Yb3+ Complexes

Author

Foster Amoah, Eastern Illinois UniversityFollow

Graduate Program

Chemistry

Degree Name

Master of Science (MS)

Semester of Degree Completion

Spring 2025

Thesis Director

Hongshan He

Thesis Committee Member

Gopal R. Periyannan

Thesis Committee Member

Zhiqing Yan

Thesis Committee Member

Cesar A. Ortiz-Ledon

Abstract

Lanthanide complexes possess unique photophysical properties such as sharp emission lines, large Stokes shifts, long luminescence lifetimes, and excellent photostability, making them ideal for applications in bioimaging, light-emitting devices, and telecommunications. Their ability to emit in the near-infrared (NIR) region (700–1700 nm) offers key advantages for medical and technological uses, including deep tissue penetration, minimal autofluorescence, reduced light scattering, high signal-to-noise ratios, and low toxicity. This study reports the synthesis and photophysical characterization of Yb³⁺ complexes across two similar projects. First, a porphyrin-based complex, [Yb(DPP)(PH)(OAc)(MeOH)], incorporating a phenylhexanone (PH) substituent, was synthesized and characterized using ¹H NMR, MS, FTIR, and UV-Vis spectroscopy. The complex exhibited visible absorption at 411 nm (Soret band) and weaker Q bands at 500 and 542 nm. Weak porphyrin fluorescence was observed at 635 and 700 nm, alongside near-infrared (NIR) emissions at 975 and 1006 nm corresponding to Yb^{3+ 2}F_5/2 → ²F_7/2 transitions. The characterization data reveal that the complex possesses a highly asymmetrical coordination environment, which facilitates enhanced radiative transitions and indicates efficient energy transfer from the coordinated ligands to the Yb³⁺ ion. In a second study, BODIPY-functionalized ligands (L1–L4) were spectroscopically titrated with [Yb(DPP)(OAc)(MeOH)₂] and [Yb(Hfac)₃(H₂O)₂] to probe energy transfer and NIR emission behavior. Ligands L1 (Phen-BDP) and L2 (BiPy-BDP) sensitized Yb³⁺ emission efficiently in both complexes via the heavy atom effect, while L3 (PA-BDP) and L4 (UR-BDP) showed selective energy transfer only in [Yb-DPP-OAc-L], mediated by a stepwise FRET process. Based on these findings, four BODIPY-Yb³⁺ complexes were synthesized, each showing visible absorption (503–506 nm) and characteristic NIR emission around 980 nm, with peak splitting due to crystal field interactions.

Recommended Citation

Amoah, Foster, "Synthesis and Spectroscopic Investigation of Sensitized Near-Infrared Emission of Yb3+ Complexes" (2025). Masters Theses. 5086.
https://thekeep.eiu.edu/theses/5086