Photophysical Properties and Energy Transfer Pathway of Er(III) Complexes with Pt−Porphyrin and Terpyridine Ligands

Abstract

The photophysical properties of Er(III) complexes coordinated with platinum[5,10,15-triphenyl-20-(4-carboxyphenyl)-porphyrin] (PtP) and terpyridine (tpy) ligands in organic solution were investigated. The Er(III) complex emitted sensitized near-IR (NIR) luminescence when the PtP ligands were excited under deoxygenated conditions. The quantum yield (PhiLn) of the sensitized luminescence was 0.015%, as evaluated from luminescence lifetime. The photophysical studies and theoretical calculations suggest that the Förster resonance mechanism is very suitable for the energy transfer from PtP to the Er(III) ion and occurred through the first triplet excited state of PtP. The 12.3% energy transfer from the triplet state to the 4F9/2 and 4I9/2 states of Er(III) occurred with a rate distribution of 3.36x10(5) and 6.67x10(4) s(-1), respectively. In addition, the observed triplet quantum yield of the PtP ligand in [Ln(PtP)3(tpy)] proved that the energy transfer from the singlet excited state of the PtP ligand to the Er(III) ion did not take place.

Dynamics of Energy Transfer from CdSe Nanocrystals to Triplet States of Anthracene Ligand Molecules

“…To achieve such an overlap, the anthracene moiety must be in close contact with the NC surface, e.g., attached by a chemical bond. In covalent organic molecular assemblies and coordination complexes with strong ligand–metal interactions, the Dexter transfer can occur on subnanosecond time scales. , For COOH-metal chelates, however, triplet energy transfer from the organic ligand to the metal center tends to occur more slowly, with rates ranging from 10 5 to 10 8 s –1 . − The rate k q = 1.5 × 10 7 s –1 obtained in this work for the reverse process (transfer from the semiconductor NC to the ligand triplet state) falls within this range. Of course, the absolute rate will depend sensitively on energy offsets, bonding, and the geometry of the orbital overlaps.…”

Syntheses, structures and photophysical properties of heteronuclear Zn–Ln coordination complexes

“…The energy gap between the excited state of the d-block and the emission states of Ln 3 þ ions is more feasible and facilitates the sensitization for the luminescence of Ln 3 þ ions especially in the near-infrared (NIR) region. For example, in Er-Ptporphyrin complex [24], with the excitation at 510 nm the energy transfers to single state of PtP (d-block ), then transfers to triplet state (T 1 ) whose energy is lowered (14600 cm À 1 ) by ISC (intersystem crossing). The energy gap between the triplet state (T 1 ) of PtP and the state ( 4 I 13/2 ) of Er 3 þ ion is small, so the waste of energy can be reduced.…”

Effects of Progressive Halogen Substitution on the Photoluminescence Properties of an Erbium−Porphyrin Complex

“…On such a basis, several erbium-containing compounds have been synthesized and characterized over the past decade, – with the aim of enhancing the near-infrared (NIR) emission and improving the physical processability and compatibility of the materials. Specifically, great attention has been paid to the investigation and engineering of the intramolecular energy transfer through the choice of specific organic ligands, as well as to reducing the quenching of the radiative emission.…”