Effective Photosensitization in Excited‐State Equilibrium: Brilliant Luminescence of Tb^III Coordination Polymers Through Ancillary Ligand Modifications

Abstract

Molecular photosensitizers provide efficient light-absorbing abilities for photo-functional materials. Herein, effective photosensitization in excited-state equilibrium is demonstrated using five Tb III coordination polymers. The coordination polymers are composed of Tb III ions (emission center), hexafluoroacetylacetonato (photosensitizer ligands), and phosphine oxide-based bridges (ancillary ligands). The two types of ligand combinations induces a rigid coordination structure via intermolecular interactions, resulting in high thermal stability (with decom-position temperatures above 300 °C). Excited-triplet-state lifetimes of photosensitizer ligands (τ = 120-1320 μs) are strongly dependent on the structure of the ancillary ligands. The photosensitizer with a long excited-triplet-state lifetime (τ � 1120 μs) controls the excited state equilibrium between the photosensitizer and Tb III , allowing the construction of Tb III coordination polymer with high Tb III emission quantum yield (� 70 %).

Effective photosensitized emission of a Tb(iii) complex using a β-diketonate photosensitizer and an oxygen barrier system in a thermally populated triplet state

“…23 Recently, we demonstrated an effective photosensitization model in the thermally populated T 1 state during Tb( iii ) emission using a typical β-diketonate (hfa: hexafluoroacetylacetonate, T 1 ∼ 22 000 cm −1 , Δ E T1-5D4 ∼ 1500 cm −1 ), with long-lived T 1 state controlled by ancillary phosphine oxide ligands. 24 The photosensitization model with a low T 1 level is beneficial for enhancing the brightness of Tb( iii ) emission (ESI in ref. 25).…”

High brightness red emitting polymer beads for immunoassays: Comparison between trifluoroacetylacetonates of Europium

“…The energetic difference (ΔE) between 3 T and 5 D 0 or 5 D 4 is most significant: if the ligand triplet is less than roughly 2000 cm -1 above 5 D 0 ( Malta et al, 1997 ) or 5 D 4 ( Latva et al, 1997 ), energy back transfer will increasingly go at the cost of efficiency. However, if ancillary ligands with low lying triplets below the antenna are present, resonant energy back transfer may occur and can even enhance the overall quantum yield ( Kitagawa et al, 2022 ). Additionally, non-radiative deactivation by co-coordinated, high frequency oscillators like H 2 O must be suppressed for high efficiency, which can be accomplished by the employment of ancillary ligands to avoid H 2 O-coordination.…”