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1. 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 (November 2024, 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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2. Photofragment imaging differentiates between one- and two-photon dissociation pathways in MgI⁺

   https://doi.org/10.1063/5.0134668  

   Lockwood, Schuyler P; Metz, Ricardo B (February 2023, The Journal of Chemical Physics)

   The bond strength and photodissociation dynamics of MgI+ are determined by a combination of theory, photodissociation spectroscopy, and photofragment velocity map imaging. From 17 000 to 21 500 cm−1, the photodissociation spectrum of MgI+ is broad and unstructured; photofragment images in this region show perpendicular anisotropy, which is consistent with absorption to the repulsive wall of the (1) Ω = 1 or (2) Ω = 1 states followed by direct dissociation to ground state products Mg+ (2S) + I (2P3/2). Analysis of photofragment images taken at photon energies near the threshold gives a bond dissociation energy D0(Mg+-I) = 203.0 ± 1.8 kJ/mol (2.10 ± 0.02 eV; 17 000 ± 150 cm−1). At photon energies of 33 000–41 000 cm−1, exclusively I+ fragments are formed. Over most of this region, the formation of I+ is not energetically allowed via one-photon absorption from the ground state of MgI+. Images show the observed product is due to resonance enhanced two-photon dissociation. The photodissociation spectrum from 33 000 to 38 500 cm−1 shows vibrational structure, giving an average excited state vibrational spacing of 227 cm−1. This is consistent with absorption to the (3) Ω = 0+ state from ν = 0, 1 of the (1) Ω = 0+ ground state; from the (3) Ω = 0+ state, absorption of a second photon results in dissociation to Mg* (3P°J) + I+ (3PJ). From 38 500 to 41 000 cm−1, the spectrum is broad and unstructured. We attribute this region of the spectrum to one-photon dissociation of vibrationally hot MgI+ at low energy and ground state MgI+ at higher energy to form Mg (1S) + I+ (3PJ) products. 

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3. Magnetic properties of two Gd ^III Fe ^III ₄ metallacrowns and strategies for optimizing the magnetocaloric effect of this topology

   https://doi.org/10.1039/D1QI00207D  

   Salerno, Elvin V.; Kampf, Jeff W.; Pecoraro, Vincent L.; Mallah, Talal (May 2021, Inorganic Chemistry Frontiers)

   Two Gd III Fe III 4 metallacrown complexes are presented and analyzed for their magnetic properties. One of these species is newly identified and exhibits a bent ring geometry as opposed to the more conventional flatter conformation of the other. Both complexes are quite similar magnetically, exhibiting antiferromagnetic exchange coupling values ca . J (Fe III –N–O–Fe III ) = −7 cm −1 and J (Gd III –O–Fe III ) = −0.7 cm −1 . When analyzed for the molecular magnetocaloric effect, maximum −Δ S m values of 7.3 J K −1 kg −1 at 3 K and at 6.1 J K −1 kg −1 at 4 K were exhibited. A detailed structural-magnetic correlation is established and an assessment of several similar magnetic metallacrowns with diverse metal combinations is given with regards to their potential magnetocaloric properties. Strategies for improving the magnetocaloric properties within the Metaln + FeIII4 family of metallacrowns are proposed regarding the ratio between coupling parameters J (Fe III –N–O–Fe III )/ J (Metal n+ –O–Fe III ). 

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4. 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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5. Targeted, Molecular Europium ^(III) Probes Enable Luminescence-Guided Surgery and 1 Photon Post-Surgical Luminescence Microscopy of Solid Tumors

   https://doi.org/10.1021/jacs.3c09444  

   Lengacher, Raphael; Martin, Kirsten E; Śmiłowicz, Dariusz; Esseln, Helena; Lotlikar, Piyusha; Grichine, Alexei; Maury, Olivier; Boros, Eszter (November 2023, Journal of the American Chemical Society)