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A family of Zn 16 Ln(HA) 16 metallacrowns (MCs; Ln = Yb III , Er III , and Nd III ; HA = picoline- (picHA 2− ), pyrazine- (pyzHA 2− ), and quinaldine- (quinHA 2− ) hydroximates) with an ‘encapsulated sandwich’ structure possesses outstanding luminescence properties in the near-infrared (NIR) and suitability for cell imaging. Here, to decipher which parameters affect their functional and photophysical properties and how the nature of the hydroximate ligands can allow their fine tuning, we have completed this Zn 16 Ln(HA) 16 family by synthesizing MCs with two new ligands, naphthyridine- (napHA 2− ) and quinoxaline- (quinoHA 2− ) hydroximates. Zn 16 Ln(napHA) 16 and Zn 16 Ln(quinoHA) 16 exhibit absorption bands extended into the visible range and efficiently sensitize the NIR emissions of Yb III , Er III , and Nd III upon excitation up to 630 nm. The energies of the lowest singlet (S 1 ), triplet (T 1 ) and intra-ligand charge transfer (ILCT) states have been determined. Ln III -centered total ( Q LLn) and intrinsic ( Q LnLn) quantum yields, sensitization efficiencies ( η sens ), observed ( τ obs ) and radiative ( τ rad ) luminescence lifetimes have been recorded and analyzed in the solid state and in CH 3 OH and CD 3 OD solutions for all Zn 16 Ln(HA) 16 . We found that, within the Zn 16 Ln(HA) 16 family, τ rad values are not constant for a particular Ln III . The close in energy positions of T 1 and ILCT states in Zn 16 Ln(picHA) 16 and Zn 16 Ln(quinHA) 16 are preferred for the sensitization of Ln III NIR emission and η sens values reach 100% for Nd III . Finally, the highest values of Q LLn are observed for Zn 16 Ln(quinHA) 16 in the solid state or in CD 3 OD solutions. With these data at hand, we are now capable of creating MCs with desired properties suitable for NIR optical imaging.
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Enabling Visible Light Sensitization of Yb III , Nd III and Er III in Dimeric Ln III /Ga III Metallacrowns through Functionalization with Ru II Complexes for NIR‐II Multiplex Imaging
Abstract Multiplex imaging in the second near‐infrared window (NIR‐II, 1000–1700 nm) provides exciting opportunities for more precise understanding of biological processes and more accurate diagnosis of diseases by enabling real‐time acquisition of images with improved contrast and spatial resolution in deeper tissues. Today, the number of imaging agents suitable for this modality remains very scarce. In this work, we have synthesized and fully characterized, including theoretical calculations, a series of dimeric LnIII/GaIIImetallacrowns bearing RuIIpolypyridyl complexes,LnRu‐3(Ln=YIII, YbIII, NdIII, ErIII). Relaxed structures ofYRu‐3in the ground and the excited electronic states have been calculated using dispersion‐corrected density functional theory methods. Detailed photophysical studies ofLnRu‐3have demonstrated that characteristic emission signals of YbIII, NdIIIand ErIIIin the NIR‐II range can be sensitized upon excitation in the visible range through RuII‐centered metal‐to‐ligand charge transfer (MLCT) states. We have also showed that these NIR‐II signals are unambiguously detected in an imaging experiment using capillaries and biological tissue‐mimicking phantoms. This work opens unprecedented perspectives for NIR‐II multiplex imaging using LnIII‐based molecular compounds.
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- Award ID(s):
- 2154116
- PAR ID:
- 10553895
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 64
- Issue:
- 3
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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