Spectroscopic and Electrochemical Trends in Divalent Lanthanides through Modulation of Coordination Environment

Jenks, Tyler C.; Kuda-Wedagedara, Akhila N. W.; Bailey, Matthew D.; Ward, Catherine; Allen, Matthew J.

doi:10.1021/acs.inorgchem.0c00136

Cited by 37 publications

(71 citation statements)

References 70 publications

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“…Cryptand complexes of the traditional divalent lanthanoids were some of the first to be investigated, with the benefit of encapsulation aiding in the stabilization of Ln II state and facilitating studies of luminescent properties through prevention of quenching by deterring inner sphere solvent coordination [58] . A recent spectroscopic and electrochemical investigation of Eu II and Yb II complexes ([Yb(N 8 L crypt )] ( 8 ), [Yb(Me 6 N 8 L crypt )] ( 9 ), [Yb(O 4 N 2 L crypt )] ( 10 ), and [Yb(PhO 4 N 2 L crypt )] ( 11 ); Scheme 1) probed the impact on the redox properties of systematic variation of the electronic and steric properties of cryptand ligands [49] . Although the Eu II analogues were previously reported, [58b,c, 59] these had not yet been investigated for Yb.…”

Section: Lanthanoid Complexes With Unusual Lanthanoid Oxidation Statesmentioning

confidence: 99%

“…Overall, similar trends in the order of redox potentials for the Yb series and the Eu series were observed, with the processes for the Yb II complexes exhibiting more negative potentials than the Eu II . The study revealed that nitrogenous donors gave rise to bathochromic shifts resulting in visible light absorption [49] …”

Section: Lanthanoid Complexes With Unusual Lanthanoid Oxidation Statesmentioning

confidence: 99%

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Lanthanoid Complexes as Molecular Materials: The Redox Approach

Hay

Boskovic

2021

Chemistry A European J

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The development of molecular materials with novel functionality offers promise for technological innovation. Switchable molecules that incorporate redox‐active components are enticing candidate compounds due to their potential for electronic manipulation. Lanthanoid metals are most prevalent in their trivalent state and usually redox‐activity in lanthanoid complexes is restricted to the ligand. The unique electronic and physical properties of lanthanoid ions have been exploited for various applications, including in magnetic and luminescent materials as well as in catalysis. Lanthanoid complexes are also promising for applications reliant on switchability, where the physical properties can be modulated by varying the oxidation state of a coordinated ligand. Lanthanoid‐based redox activity is also possible, encompassing both divalent and tetravalent metal oxidation states. Thus, utilization of redox‐active lanthanoid metals offers an attractive opportunity to further expand the capabilities of molecular materials. This review surveys both ligand and lanthanoid centered redox‐activity in pre‐existing molecular systems, including tuning of lanthanoid magnetic and photophysical properties by modulating the redox states of coordinated ligands. Ultimately the combination of redox‐activity at both ligands and metal centers in the same molecule can afford novel electronic structures and physical properties, including multiconfigurational electronic states and valence tautomerism. Further targeted exploration of these features is clearly warranted, both to enhance understanding of the underlying fundamental chemistry, and for the generation of a potentially important new class of molecular material.

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Section: Lanthanoid Complexes With Unusual Lanthanoid Oxidation Statesmentioning

confidence: 99%

Section: Lanthanoid Complexes With Unusual Lanthanoid Oxidation Statesmentioning

confidence: 99%

Lanthanoid Complexes as Molecular Materials: The Redox Approach

Hay

Boskovic

2021

Chemistry A European J

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“…Evidence that the ligand environment alters the Ln(III)/Ln(II) redox potential is abundant. Cryptands with soft donor atoms can stabilize Eu(II) − and Yb(II) . Eu(III) centers in different ligand environments may differ in their redox potentials by as much as 1.4 V .…”

Section: Introductionmentioning

confidence: 99%

Coordination Environment-Controlled Photoinduced Electron Transfer Quenching in Luminescent Europium Complexes

et al. 2020

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The quenching of sensitized Eu(III) luminescence by photoinduced electron transfer from the excited light-harvesting antenna to Eu(III) was investigated. A series of complexes incorporating different metal binding sites and thus having varying Eu(III)/Eu(II) reduction potentials were prepared. The complexes were fully characterized using a combination of single-crystal X-ray crystallography and paramagnetic 1H NMR spectroscopy, the results of which support the structural similarity of the complexes. The redox and photophysical behavior of the Eu(III) center and the light-harvesting antenna were studied using cyclic voltammetry and steady-state and time-resolved emission spectroscopy on the nanosecond and millisecond time scales. The contribution of photoinduced electron transfer to the overall reduction of the Eu(III) luminescence quantum yield was found to be comparable and, in many cases, larger than the quenching caused by well-established processes such as coupling to X–H oscillators. These results suggest that the elimination or mitigation of photoinduced electron transfer could substantially improve the emissive properties of the widely used Eu(III)-based emitters.

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“…A variety of such metal complexes have been crystallographically-characterized involving both divalent and trivalent ions usually with one or two additional coordinated ligands that could be anions or neutral species. Examples include [Ln II (crypt)(THF) x ][Cp′ 3 Ln] (x = 1, Ln = Sm, Eu; x = 0, Ln = Yb), 30 [Sm II (crypt) (DippForm)][DippForm] (DippForm = N,N′-bis(2,6-diisopropylphenyl)-formamidinate), 31 [Sm II (crypt)(PCO) 2 ], 31 [Eu II (crypt) Cl][Cl], 32 [Yb II (crypt)I][I], 33 [Ln III (crypt)(THF)][BPh 4 ] 2 (Ln = Sm, Eu), 34 [La III (crypt)Cl 2 ][Cl], 35 [Ln II (crypt)(DMF) x ][X] 2 (x = 2, Ln = Sm, Eu; x = 1, Ln = Yb; X = I, BPh 4 ), 36 [Ln III (crypt)(OTf) 2 ][OTf] and [Ln II (crypt)(OTf) 2 ] (Ln = Nd, Sm) 37 among others. [38][39][40][41][42] We report here a new coordination mode for crypt with rareearth metal ions that is intermediate between the two modes described above, i.e.…”

Section: Introductionmentioning

confidence: 99%