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1. Peculiarities of crystal structures and photophysical properties of Ga ^III /Ln ^III metallacrowns with a non-planar [12-MC-4] core

   https://doi.org/10.1039/c9qi01647c  

   Nguyen, Tu N.; Eliseeva, Svetlana V.; Chow, Chun Y.; Kampf, Jeff W.; Petoud, Stéphane; Pecoraro, Vincent L. (March 2020, Inorganic Chemistry Frontiers)

   A new series of gallium( iii )/lanthanide( iii ) metallacrown (MC) complexes ( Ln-1 ) was synthesized by the direct reaction of salicylhydroxamic acid (H 3 shi) with Ga III and Ln III nitrates in a CH 3 OH/pyridine mixture. X-ray single crystal analysis revealed two types of structures depending on whether the nitrate counterion coordinate or not to the Ln III : [LnGa 4 (shi) 4 (H 2 shi) 2 (py) 4 (NO 3 )](py) 2 (Ln = Gd III , Tb III , Dy III , Ho III ) and [LnGa 4 (shi) 4 (H 2 shi) 2 (py) 5 ](NO 3 )(py) (Ln = Er III , Tm III , Yb III ). The representative Tb-1 and Yb-1 MCs consist of a Tb/YbGa 4 core with four [Ga III –N–O] repeating units forming a non-planar ring that coordinates the central Ln III through the oxygen atoms of the four shi 3− groups. Two H 2 shi − groups bridge the Ln III to the Ga III ring ions. The Yb III in Yb-1 is eight-coordinated while the ligation of the nine-coordinated Tb III in Tb-1 is completed by one chelating nitrate ion. Ln-1 complexes in the solid state showed characteristic sharp f–f transitions in the visible (Tb, Dy) and near-infrared (Dy, Ho, Er, Yb) spectral ranges upon excitation into the ligand-centered electronic levels at 350 nm. Observed luminescence lifetimes and absolute quantum yields were collected and discussed. For Yb-1 , luminescence data were also acquired in CH 3 OH and CD 3 OD solutions and a more extensive analysis of photophysical properties was performed. This work demonstrates that while obtaining highly luminescent lanthanide( iii ) MCs via a direct synthesis is feasible, many factors such as molar absorptivities, triplet state energies, non-radiative deactivations through vibronic coupling with overtones of O–H, N–H, and C–H oscillators and crystal packing will strongly contribute to the luminescent properties and should be carefully considered. 

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2. Luminescent lanthanide complexes with a pyridine-bis(carboxamide)-bithiophene sensitizer showing wavelength-dependent singlet oxygen generation

   https://doi.org/10.1039/d0dt01034k  

   Johnson, Katherine R.; Vittardi, Sebastian B.; Gracia-Nava, Manuel A.; Rack, Jeffrey J.; de Bettencourt-Dias, Ana (May 2020, Dalton Transactions)

   A new pyridine-bis(carboxamide)-based ligand with a bithiophene pendant, 2Tcbx, was synthesized. Its lanthanide ion (Ln III ) complexes, [Ln(2Tcbx) 2 ] 3+ , were isolated and their photophysical properties were explored. Upon excitation at 360 nm, these complexes display emission in the near-infrared (NIR) with efficiencies of 0.69% for Ln III = Yb III , 0.20% for Ln III = Nd III , and 0.01% for Ln III = Er III , respectively. Concurrent 1 O 2 formation was seen for all complexes, with efficiencies of 19% for the Yb III complex, 25% for the Nd III complex, and 9% for the Er III complex. When exciting at a longer wavelength, 435 nm, only Ln III emission was observed and larger efficiencies of Ln III -centered emission were obtained. The lack of 1 O 2 generation indicates that energy pathways involving different ligand conformations, which were investigated by transient absorption spectroscopy, are involved in the sensitization process, and enable the wavelength-dependent generation of 1 O 2 . 

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3. 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

   https://doi.org/10.1002/anie.202416101  

   Bădescu‐Singureanu, Codruţa C; Nizovtsev, Anton S; Pecoraro, Vincent L; Petoud, Stéphane; Eliseeva, Svetlana V (January 2025, Angewandte Chemie International Edition)

   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 Ln^III/Ga^IIImetallacrowns bearing Ru^IIpolypyridyl complexes,LnRu‐3(Ln=Y^III, Yb^III, Nd^III, Er^III). 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 Yb^III, Nd^IIIand Er^IIIin the NIR‐II range can be sensitized upon excitation in the visible range through Ru^II‐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 Ln^III‐based molecular compounds. 

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4. Yb ³⁺ Sensitized Er ³⁺ Upconversion Phosphors for Noninvasive Luminescence‐Based Optical Thermometry

   https://doi.org/10.1111/jace.70774  

   Talewar, Rupesh A; Williams, Marcus; Bennett, Kevin; Reddy, B Rami (May 2026, Journal of the American Ceramic Society)

   ABSTRACT Rare earth ion doped Zn₂P₂O₇phosphor was synthesized via a solid‑state reaction route. XRD measurements confirmed the formation of a single‑phase Zn₂P₂O₇lattice. Sensitization of Er³⁺(⁴I_13/2→⁴I_15/2) near‑infrared emission by Yb³⁺ions via an energy transfer process under 980 nm excitation is discussed. Energy transfer upconversion (ETU) was also investigated in Er³⁺and Er³⁺/Yb³⁺co‑doped Zn₂P₂O₇phosphors. Intense upconversion (UC) emissions were observed from Er³⁺in the green (520–570 nm) and red (640–680 nm) regions under 980 nm diode laser excitation. Fluorescence intensity ratio (FIR)‐based thermometry was explored using both thermally coupled levels (TCL) and non‑thermally coupled levels (NTCL). The material exhibits a consistent temperature‑dependent luminescence response with high relative sensitivity (S_R) over the investigated temperature range. The experimentally determined temperature resolution reaches 1 K at room temperature and 2.1 K at 390 K under practical measurement conditions, demonstrating reliable thermometric performance over a wide temperature range. These results provide critical insights into temperature‐dependent luminescence characteristics and establish Zn₂P₂O₇:Er³⁺,Yb³⁺as a promising candidate for the next‐generation photonic and sensors applications. 

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5. New up-conversion luminescence in molecular cyano-substituted naphthylsalophen lanthanide( iii ) complexes

   https://doi.org/10.1039/D0CC08128K  

   Monteiro, Jorge H.; Hiti, Ethan A.; Hardy, Emily E.; Wilkinson, Grant R.; Gorden, John D.; Gorden, Anne E.; de Bettencourt-Dias, Ana (March 2021, Chemical Communications)

   null (Ed.)

   A new naphthylsalophen and its 3 : 2 ligand-to-lanthanide sandwich-type complexes were isolated. When excited at 380 nm, the complexes display the characteristic metal-centred emission for Nd III , Er III and Yb III . Upon 980 nm excitation, in mixed lanthanide and the Er complexes, Er-centred upconversion emission at 543 and 656 nm is observed, with power densities as low as 2.18 W cm −2 . 

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