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1. X-ray crystallographic, luminescence and NMR studies of phenacyldiphenylphosphine oxide with the Ln( iii ) ions Sm, Eu, Gd, Tb and Dy

   https://doi.org/10.1039/c7dt02678a  

   G. Leach, Erin; Shady, Justin R.; Boyden, Adam C.; Emig, Anne-lise; Henry, Alyssa T.; Connor, Emily K.; Staples, Richard J.; Schaertel, Stephanie; Werner, Eric J.; Biros, Shannon M. (January 2017, Dalton Transactions)

   We report here the characterization in solution (NMR, luminescence, MS) and the solid-state (X-ray crystallography, IR) of complexes between phenacyldiphenylphosphine oxide and five Ln( iii ) ions (Sm, Eu, Gd, Tb, Dy). Four single crystal X-ray structures are described here showing a 1 : 2 ratio between the Ln 3+ ions Eu, Dy, Sm and Gd and the ligand, where the phosphine oxide ligands are bound in a monodentate manner to the metal center. A fifth structure is reported for the 1 : 2 Eu(NO 3 ) 3 -ligand complex showing bidentate binding between the two ligands and the metal center. The solution coordination chemistry of these metal complexes was probed by 1 H, 13 C and 31 P NMR, mass spectrometry, and luminescence experiments. The title ligand has the capability to sensitize Tb 3+ , Dy 3+ , Eu 3+ and Sm 3+ leading to metal-centered emission in solutions of acetonitrile and methanol and in the solid state. 

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2. 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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3. Vanol‐Supported Lanthanide Complexes for Strong Circularly Polarized Luminescence at 1550 nm

   https://doi.org/10.1002/chem.202300800  

   Adewuyi, Joseph A.; Schley, Nathan D.; Ung, Gaël (May 2023, Chemistry – A European Journal)

   Abstract Strong circularly polarized luminescence (CPL) at 1550 nm is reported for lanthanide complexes supported by Vanol; these are the first examples of coordination of Vanol to lanthanides. A change in the ligand design from a 1,1’‐bi‐2‐naphthol (in Binol) to a 2,2’‐bi‐1‐naphthol (in Vanol) results in significantly improved dissymmetry factors for (Vanol)₃ErNa₃(|g_lum|=0.64) at 1550 nm. This is among the highest reported dissymmetry factors to date in the telecom C‐band region, and among the highest for any lanthanide complexes. Comparative solid‐state structural analysis of (Vanol)₃ErNa₃and (Binol)₃ErNa₃suggests that a less distorted geometry around the metal center is in part responsible for the high chiroptical metrics of (Vanol)₃ErNa₃. This phenomenon was further evidenced in the analogous ytterbium complex (Vanol)₃YbNa₃that also exhibit a significantly improved dissymmetry factor (|g_lum|=0.21). This confirms and generalizes the same observation that was made in other visibly emitting, six‐coordinate lanthanide complexes. Due to their strong CPL at 1550 nm, the reported complexes are potential candidates for applications in quantum communication technologies. More importantly, our structure‐CPL activity relationship study provides guidance towards the generation of even better near‐infrared CPL emitters. 

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4. Evaluating electrochemical accessibility of 4f ⁿ 5d ¹ and 4f ⁿ⁺¹ Ln( ii ) ions in (C ₅ H ₄ SiMe ₃ ) ₃ Ln and (C ₅ Me ₄ H) ₃ Ln complexes

   https://doi.org/10.1039/D1DT02427B  

   Trinh, Michael T.; Wedal, Justin C.; Evans, William J. (October 2021, Dalton Transactions)

   The reduction potentials (reported vs. Fc + /Fc) for a series of Cp′ 3 Ln complexes (Cp′ = C 5 H 4 SiMe 3 , Ln = lanthanide) were determined via electrochemistry in THF with [ n Bu 4 N][BPh 4 ] as the supporting electrolyte. The Ln( iii )/Ln( ii ) reduction potentials for Ln = Eu, Yb, Sm, and Tm (−1.07 to −2.83 V) follow the expected trend for stability of 4f 7 , 4f 14 , 4f 6 , and 4f 13 Ln( ii ) ions, respectively. The reduction potentials for Ln = Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu, that form 4f n 5d 1 Ln( ii ) ions ( n = 2–14), fall in a narrow range of −2.95 V to −3.14 V. Only cathodic events were observed for La and Ce at −3.36 V and −3.43 V, respectively. The reduction potentials of the Ln( ii ) compounds [K(2.2.2-cryptand)][Cp′ 3 Ln] (Ln = Pr, Sm, Eu) match those of the Cp′ 3 Ln complexes. The reduction potentials of nine (C 5 Me 4 H) 3 Ln complexes were also studied and found to be 0.05–0.24 V more negative than those of the Cp′ 3 Ln compounds. 

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5. Triple Inverse Sandwich versus End-On Diazenido: Bonding Motifs across a Series of Rhenium–Lanthanide and –Actinide Complexes

   https://doi.org/10.1021/acs.inorgchem.3c04248  

   Ouellette, Erik T; Brackbill, I Joseph; Kynman, Amy E; Christodoulou, Stella; Maron, Laurent; Bergman, Robert G; Arnold, John (April 2024, Inorganic Chemistry)

   While synthesizing a series of rhenium–lanthanide triple inverse sandwich complexes, we unexpectedly uncovered evidence for rare examples of end-on lanthanide dinitrogen coordination for certain heavy lanthanide elements as well as for uranium. We begin our report with the synthesis and characterization of a series of trirhenium triple inverse sandwich complexes with the early lanthanides, Ln[(μ-η5:η5-Cp)Re(BDI)]3(THF) (1-Ln, Ln = La, Ce, Pr, Nd, Sm; Cp = cyclopentadienide, BDI = N,N′-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate). However, as we moved across the lanthanide series, we ran into an unexpected result for gadolinium in which we structurally characterized two products for gadolinium, namely, 1-Gd (analogous to 1-Ln) and a diazenido dirhenium double inverse sandwich complex Gd[(μ-η1:η1-N2)Re(η5-Cp)(BDI)][(μ-η5:η5-Cp)Re(BDI)]2(THF)2 (2-Gd). Evidence for analogues of 2-Gd was spectroscopically observed for other heavy lanthanides (2-Ln, Ln = Tb, Dy, Er), and, in the case of 2-Er, structurally authenticated. These complexes represent the first observed examples of heterobimetallic end-on lanthanide dinitrogen coordination. Density functional theory (DFT) calculations were utilized to probe relevant bonding interactions and reveal energetic differences between both the experimental and putative 1-Ln and 2-Ln complexes. We also present additional examples of novel end-on heterobimetallic lanthanide and actinide diazenido moieties in the erbium–rhenium complex (η8-COT)Er[(μ-η1:η1-N2)Re(η5-Cp)(BDI)](THF)(Et2O) (3-Er) and uranium–rhenium complex [Na(2.2.2-cryptand)][(η5-C5H4SiMe3)3U(μ-η1:η1-N2)Re(η5-Cp)(BDI)] (4-U). Finally, we expand the scope of rhenium inverse sandwich coordination by synthesizing divalent double inverse sandwich complex Yb[(μ-η5:η5-Cp)Re(BDI)]2(THF)2 (5-Yb), as well as base-free, homoleptic rhenium–rare earth triple inverse sandwich complex Y[(μ-η5:η5-Cp)Re(BDI)]3 (6-Y). 

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