Series Of Lanthanide Complexes Research Articles

A series of lanthanide complexes with different aromatic carboxylic acid ligands: Synthesis, supramolecular structure, thermal properties and luminescence behaviors

Six noble two-dimensional lanthanide complexes [Ln(2,4-DFBA)3(terpy)·H2O]·H2O (Ln = Tb(1), Dy(2)), [Pr(2,4,6-TMBA)3(terpy)·H2O] (3) [Nd(2,4,6-TMBA)3(terpy)·H2O]·C2H5OH·H2O(4) and [Ln(2,4,6-TMBA)3(terpy)·H2O]·1.5H2O (Ln = Dy(5), Ho(6) (2,4-DFBA = 2,4-difluorobenzoate, 2,4,6-TMBA = 2,4,6-trimethylbenzoate, terpy = 2,2 ': 6′, 2 ''- terpyridine) were synthesized by conventional solution method with 2,4-difluorobenzoic acid and 2,4,6-trimethylbenzoic acid as main ligands and 2,2 ': 6′, 2 ''- terpyridine as auxiliary ligands. The complexes were characterized by infrared spectroscopy and Raman spectroscopy, and the thermal decomposition mechanism of the complex was studied by TG-DTG-DSC/FTIR coupling technology. The solid fluorescence test was also carried out for complexes 1,2 and 4. It was found that the complexes have good fluorescence properties, and the fluorescence lifetime of complex 1 was 0.541 ms.

Optical, electrochemical and photophysical analyses of heteroleptic luminescent Ln(iii) complexes for lighting applications.

A series of lanthanide complexes have been synthesized with fluorinated 1,3-diketones and heteroaromatic ancillary moieties. Spectroscopic studies reveal the attachment of the respective lanthanide ion to the oxygen site of β-diketone and nitrogen site of auxiliary moieties. The conducting behavior of the complexes is proposed by their optical energy gaps which lie in the range of semiconductors. The emission profiles of the lanthanide complexes demonstrate red and green luminescence owing to the distinctive transitions of Sm3+ and Tb3+ ions, respectively. Energy transfer via antenna effect clearly reveals the effective transfer of energy from the chromophoric moiety to the Ln3+ ion. The prepared conducting and luminescent Ln(iii) complexes might be employed as the emitting component in designing OLEDs.

Six-coordinated rare earth organoarsinate complexes: Crystal structure, luminescent and magnetic properties investigation

An isostructural series of rare earth complexes has been synthesized by using the dimethylarsinate ligand. All complexes have the formula [Ln(Me2AsO2)3][H2O]8 (Ln ​= ​Sm(1), Eu(2), Gd(3), Tb(4), Dy(5), Ho(6), Er(7), Tm(8), Yb(9), Y(10)). They are the first rare earth complexes ligated by organoarsinate. Crystallographic characterizations reveal that all the compounds feature 1D chain-like arrangements, in which two rare earth ions are bounded by three dimethylarsinate ligands (syn,syn, μ2-ƞ1:ƞ1) and the rare six-coordinated rare earth ions display ideal octahedron coordination geometry. The solid state photoluminescent studies reveal that compounds 2 and 4 exhibit the characteristic emission band of the EuIII and TbIII ions respectively. Magnetic measurements indicate Gd(3) shows magnetocaloric effect (MCE) with entropy change of 24.92 ​J ​kg–1 K–1 for ΔH ​= ​0 – 7 ​T at 3 ​K. The Dy(5) and Yb(9) show field induced slow relaxation, which is rare for octahedron coordinate LnIII compounds.

Study of the most relevant spin-orbit coupling descriptions of magnetic excitations in a series of lanthanide complexes.

We present a number of computationally cost-effective approaches to calculate magnetic excitations (i.e. crystal field energies and magnetic anisotropies in the lowest spin-orbit multiplet) in lanthanide complexes. In particular, we focus on the representation of the spin-orbit coupling term of the molecular Hamiltonian, which has been implemented within the quantum chemistry package CERES using various approximations to the Breit-Pauli Hamiltonian. The approximations include the (i) bare one-electron approximation, (ii) atomic mean field and molecular mean field approximations of the two-electron term, (iii) full representation of the Breit-Pauli Hamiltonian. Within the framework of the CERES implementation, the spin-orbit Hamiltonian is always fully diagonalized together with the electron repulsion Hamiltonian (CASCI-SO) on the full basis of Slater determinants arising within the 4f ligand field space. For the first time, we make full use of the Cholesky decomposition of two-electron spin-orbit integrals to speed up the calculation of the two-electron spin-orbit operator. We perform an extensive comparison of the different approximations on a set of lanthanide complexes varying both the lanthanide ion and the ligands. Surprisingly, while our results confirm the need of at least a mean field approach to accurately describe the spin-orbit coupling interaction within the ground Russell-Saunders term, we find that the simple bare one-electron spin-orbit Hamiltonian performs reasonably well to describe the crystal field split energies and g tensors within the ground spin-orbit multiplet, which characterize all the magnetic excitations responsible for lanthanide-based single-molecule magnetism.

Lanthanide complexes with polyaminopolycarboxylates as prospective NMR/MRI diagnostic probes: peculiarities of molecular structure, dynamics and paramagnetic properties.

The paramagnetic lanthanide complexes with polyaminopolycarboxylate (PAPC) ligands attract considerable attention from the standpoint of potential applications thereof as relaxation agents used in medical magnetic resonance imaging (MRI) and in luminescent materials, as well as owing to promising use thereof as paramagnetic labels for studying the properties of biopolymers since they exhibit thermodynamic stability, good solubility in aqueous media and moderate toxicity. For the last decades, the NMR methods have been used to determine the physical and chemical properties of paramagnetic Ln compounds. The studies concerning paramagnetic NMR lanthanide-induced shifts (LISs) in dissolved Ln complexes, as well as the analysis of band shape as a function of temperature make it possible to obtain valuable information on the structure, intra- and intermolecular dynamics and paramagnetic properties thereof. This review is devoted solely to the following features: firstly, the processes of intramolecular dynamics of lanthanide complexes with polyamino-polycarboxylate ligands such as DOTA, EDTA and DTPA and their derivatives studied by NMR; secondly, the LISs of lanthanide complexes with EDTA, DOTA, DTPA and some of their derivatives depending on temperature and pH. Moreover, in this review, for the first time, the dependence of the activation energy of molecular dynamics in complexes with polydentate ligands on the atomic number of the lanthanide cation is analyzed and a monotonic change in energy is detected, which is due to the effect of lanthanide contraction. It should be noted that this phenomenon is quite general and may also appear in the future in many other series of lanthanide complexes with both other multidentate ligands and with bidentate and monodentate ligands. In the future, it is possible to predict the dependence of the properties of certain lanthanide complexes on the ionic radius of the lanthanide cation based on the approaches presented in the review. In this review, we have also presented the dynamic NMR as the main research method widely used to analyze the processes of molecular dynamics, and the structural studies based on the NMR relaxation spectroscopy and LIS analysis.

Intrinsic anisotropy parameters of a series of lanthanoid complexes deliver new insights into the structure-magnetism relationship

Intrinsic anisotropy parameters of a series of lanthanoid complexes deliver new insights into the structure-magnetism relationship

Intermolecular interactions, photocatalysis and THz-TDS interrelationships for lanthanide phosphine oxide complexes based on {PW12}

A series of rare earth complexes containing (α-PW12O40)3- and PO ligand are synthesized by water bath in 70 °C, [Ln(OPPh3)4(H2O)3](PW12O40)·4CH3CN (Ln = La, Pr, Nd, Sm, Gd, Tb, Ho 1–7) (OPPh3 = Triphenylphosphine oxide, {PW12} = phosphotungstic acid). The precise structures are confirmed by X-ray single crystal diffraction and the result shows all complexes are isostructural. Complexes 1–7 are fully characterized by PXRD, FT-IR, TGA, UV diffuse reflectance spectra and terahertz time-domain spectroscopy (THz-TDS). Complex 3 exhibits the highest photocatalytic degradation efficiency for methylene blue (MB) in this series of complexes. The experimental results showed that the photodegradation efficiency can remain constant at the level of 95% after five consecutive cycles. The photocatalytic reaction kinetics and mechanism of complexes were investigated. Additionally, complexes also exhibit photocatalytic hydrogen evolution activity. THz-TDS was used to characterize the complexes and its raw materials, the characteristic peaks of OPPh3 (broad peak at 1.20 THz) and phosphotungstic acid (sharp peaks at 0.23, 0.32 THz) were obtained.

A series of lanthanide complexes with 2-fluorobenzoic acid and 5,5′-dimethyl-2,2′-bipyridine: Synthesis, supramolecular structures, spectroscopy and thermal behaviour

A family of lanthanide-based self-assembling complexes constructed from 2-fluorobenzoic acid and 5,5′-dimethyl-2,2′-bipyridine have been successfully fabricated via conventional synthesis, namely, [Ln(2-FBA)3(5,5′-DM-2,2′-bipy)]2 (2-FBA = 2-fluorobenzoate, 5,5′-DM-2,2′-bipy = 5,5′-dimethyl-2,2′-bipyridine, Ln = La(1), Pr(2), Nd(3), Sm(4), Gd(5), Dy(6), Ho(7), Er(8)). The obtained complexes are investigated by means of elemental analysis, IR spectra, Raman spectra and single-crystal X-ray diffraction. Crystallographic results exhibit that each Ln3+ ion of them is located in a distorted Muffin coordination sphere finished by seven oxygen atoms of 2-FBA ligands and two nitrogen atoms of 5,5′-DM-2,2′-bipy ligand. Interestingly, although complexes 1–6 and 7–8 have the same formula unit, the differences in hydrogen bond interactions lead to different supramolecular structures. Besides, the thermal decomposition mechanism of the complexes has been studied by TG/DSC-FTIR technology. The results show that these complexes are thermally stable up to 450 K. In addition, complexes 4 and 6 both exhibit the characteristic fluorescence of lanthanide ions, that is, complex 4 exhibits characteristic 4G5/2→6HJ/2 (J = 5, 7, 9) transitions, and complex 6 shows characteristic 4F9/2→6HJ/2 (J = 15, 13) transitions.

Radii-dependent self-assembly polynuclear lanthanide complexes as catalysts for CO2 transformation into cyclic carbonates

A series of lanthanide complexes with structural variation from a dinuclear to pentanuclear structure are found to be dependent on the radii of Ln3+ ions, and show high catalytic performance to obtain cyclic carbonates under solvent-free conditions.

Effect of the nature of lanthanide on intramolecular C-F→Ln dative interactions in hexafluoroisopropoxide complexes

Electronic structures of a series oflanthanide complexes with hexafluoroisopropoxide ligands [Ln(OCH(CF3)2)2(μ2-OCH(CF3)2)(DME)]2 (Ln = Ce, Sm, Tm, Yb; DME is dimethoxyethane) were studied by quantum chemical calculations at the density functional theory (DFT) level. Intramolecular C-F→Ln interactions are present in all these compounds. A decrease in the ionic radius of lanthanide in the series from Ce to Yb leads to an increase in the degree of filling of the coordination sphere from 92.9(2) to 97.3(2)%, resulting in a systematic decrease in the delocalization index between lanthanide and fluorine atoms. An experimental-theoretical study of the complexes using a molecular invariom provided an estimate of the energy of Ln⋯F interactions, which also decreases for the complexes of the late lanthanides (Tm, Yb) compared with the complexes of the early lanthanides (Ce, Sm). Geometry optimization of the isolated molecule leads to an increase in the number of non-covalent interactions involving fluorine atoms (F⋯F, F⋯H, and F⋯O) and in their energy compared to the molecular invariom. The topological characteristics of electron density in the coordination sphere of lanthanide atoms determined by quantum chemical calculations are in good agreement with those estimated using the molecular invariom.

A semiempirical approach toward the origin of f-element binding selectivity of pyridine-2,6-diylbis(diphenylphosphine oxide)

The geometries of a series of lanthanide complexes with phosphine oxide-type ligands (either mono- or polydentate) were optimized using the PM6/Sparkle semiempirical computational approach. The activation barriers of coordination reactions (i.e. the conversion of a complex with κ1-bound ligand into a complex with multiply bound one) were estimated. The κ2-chelate formation with a pyridine-2,6-diylbis(diphenylphosphine oxide) ligand is favorable only for a few largest lanthanides, while κ1-coordination is the most probable case for the smaller ones.

A series of lanthanide complexes with 2,4-dimethylbenzoic acid and 2,2:6′,2″-terpyridine: Supramolecular structures, thermal decomposition mechanism and photoluminescence

Six new binuclear lanthanide complexes [Ln(2,4-DMBA)3(terpy)(H2O)]2 (Ln = Eu (1), La (2), Pr (3), Nd (4), Sm (5), Gd (6)) (2,4-DMBA = 2,4-dimethylbenzoate; terpy = 2,2:6′,2″-terpyridine) and four mononuclear complexes [Ln(2,4-DMBA)3(terpy)(H2O)] (Ln = Dy (7), Ho (8), Er (9), Tb (10)) have been synthesized. Complexes 1–6 and 7–10 are isomorphous, adopting interesting structures. In the structures of complexes 1–6, two nine-coordinated Ln(III) centers are linked by two 2,4-DMBA ligands in bridging mode. The other two 2,4-DMBA ligands coordinate with one Ln(III) cation in monodentate and chelating modes. In the structures of complexes 7–10, the Ln(III) center is eight-coordinated. Complexes 1–6 and 7–10 can each aggregate to form one-dimensional and two-dimensional supramolecular structures. Thermal decomposition of complexes 1–10 has been investigated by TG-DSC/FTIR. Interestingly, all of the complexes exhibit a similar three-step decomposition process. The Eu(III) and Tb(III) complexes show strong red and green visible light luminescence. Finally, fluorescence lifetimes and intrinsic quantum yields have been calculated for complexes 1 and 10.

Forcing Dicyanamide Coordination to f-Elements by Dissolution in Dicyanamide-Based Ionic Liquids.

A robust general route to lanthanide dicyanamide (DCA–) complexes has been developed where f-element salts are dissolved in DCA–-based ionic liquids (ILs) directly or formed in situ, forcing coordination of these normally weakly coordinating soft N-donor anions, even in an ambient, non-moisture-excluding environment. A series of lanthanide complexes [C2mim][Ln(DCA)4(H2O)4] (C2mim = 1-ethyl-3-methylimidazolium; Ln = La, Nd, Eu, Tb, Dy, and Yb) and [C2mim]3n[La(OH2)4(μ2-DCA)4]n[La(OH2)2(μ3-DCA)3(μ2-DCA)4]2n(Cl)4n were crystallized under a variety of conditions using this methodology and structurally characterized using single crystal X-ray diffraction. Although not all examples were isostructural, the dominant feature across the series was the presence of [Ln(DCA)4(H2O)4]− anionic nodes with all terminal DCA– ligands accepting hydrogen bonds from the coordinated water molecules forming a 3D metal organic framework. To determine if any structural clues might aid in the further development of the synthetic methodology, the metal-free IL [C1mim][DCA] (C1mim = 1,3-dimethylimidazolium), a room-temperature solid, crystalline analogue of the reaction IL, which is liquid at room temperature, was also prepared and structurally characterized. The ready isolation of these compounds allowed us to begin an investigation of the physical properties such as the luminescence at room and low temperatures for the Eu, Tb, and Dy representatives.

Combination of single-molecule magnet behaviour and luminescence properties in a new series of lanthanide complexes with tris(pyrazolyl)borate and oligo(β-diketonate) ligands.

A series of tris(pyrazolyl)borate mono-, di- and trinuclear complexes, [Tp2Ln]nX (Ln = Eu, Tb, Gd, Dy, Xn- = various mono-, bis- and tris(β-diketonates) has been prepared. The Tb3+ and Dy3+ complexes are luminescent single molecular magnets (SMM) and exhibit luminescence quantum efficiencies up to 73% for the Tb3+ and 4.4% for the Dy3+ compounds. Similar Eu3+ complexes display bright emission only at lower temperatures. The Dy3+ and Tb3+ complexes possess SMM behavior in a non-zero dc field at low temperatures, while the polynuclear Dy3+ complexes also show slow magnetic relaxation even in zero dc field up to 8 K. Ueff-values determined from dynamic magnetic measurements were up to 31 and 6 cm-1 for the Dy3+ and Tb3+ complexes, respectively. It was found that within a series of Dy3+ and Tb3+ compounds, Ueff and luminescence quantum yields decreased with increasing nuclearity of the compounds and a shortening of the intramolecular Ln-Ln distance. ΔOrbach-values estimated from low-temperature luminescence spectra were significantly higher than those obtained from ac magnetic data, which may be due to involvement of additional processes in the relaxation mechanism (quantum tunneling, Raman, direct) reducing the energy barrier. Some of the Tb3+-compounds also display metal-centred electroluminescence, giving them potential as emitting layers in LEDs.

Derivation of Lanthanide Series Crystal Field Parameters From First Principles.

Two series of lanthanide complexes have been chosen to analyze trends in the magnetic properties and crystal field parameters (CFPs) along the two series: The highly symmetric LnZn16 (picHA)16 series (Ln=Tb, Dy, Ho, Er, Yb; picHA=picolinohydroxamic acid) and the [Ln(dpa)3 ](C3 H5 N2 )3 ⋅3H2 O series (Ln=Ce-Yb; dpa=2,6-dipicolinic acid) with approximate three-fold symmetry. The first series presents a compressed coordination sphere of eight oxygen atoms whereas in the second series, the coordination sphere consists of an elongated coordination sphere formed of six oxygen atoms. The CFPs have been deduced from ab initio calculations using two methods: The AILFT (ab initio ligand field theory) method, in which the parameters are determined at the orbital level, and the ITO (irreducible tensor operator) decomposition, in which the problems are treated at the many-electron level. It has been found that the CFPs are transferable from one derivative to another, within a given series, as a first approximation. The sign of the second-order parameter differs in the two series, reflecting the different environments. It has been found that the use of the strength parameter S allows for an easy comparison between complexes. Furthermore, in both series, the parameters have been found to decrease in magnitude along the series, and this decrease is attributed to covalent effects.

A new series of lanthanide complexes with the trans-disubstituted Py2[18]aneN6 macrocyclic ligand: synthesis, structures and properties

New lanthanide complexes with the trans-disubstituted macrocyclic ligand Py2[18]aneN6 (denoted as L1) were successfully synthesized. The coordination properties of compound L1 towards different lanthanide metal ions (Ln = La–Yb, except Lu) were explored, and structural studies have been carried out both in the solid state and in aqueous solution. In all cases, complexes with a 1:1 metal:ligand molar ratio were obtained. The crystalline structures of the following compounds: [H4L1](NO3)4, [CeL1(NO3)2](NO3) and [SmL1(NO3)2](NO3) have been characterized by single crystal X-ray diffraction. In both complexes, the asymmetric unit contains the cation complex [LnL1(NO3)2]+ (Ln = Ce3+, Sm3+) which consist of a mononuclear endomacrocyclic backbone whilst the ten coordination environment is completed by two bidentade nitrate ions. The two five membered chelate rings formed by the ethylenediamine moieties adopt (δδ) [or (λλ)] conformations and also presented a C2 symmetry (as observed in solution by NMR).

Dysprosium Compounds with Hula-Hoop-like Geometries: The Influence of Magnetic Anisotropy and Magnetic Interactions on Magnetic Relaxation

Single-ion anisotropy is one of the crucial properties for mononuclear and even polynuclear single-molecule magnets (SMMs), which can be enhanced by the judicious choice of the coordination geometry around the metal centers. Meanwhile, magnetic interactions also play a significant role in high-performance polynuclear SMMs, especially the dinuclear SMMs. For exploring the influence of those two factors on the magnetic properties, we report a novel series of lanthanide complexes, [Dy(L)3(HL)(THF)2] (1), [Dy2(Py3CO)2(CF3SO3)4(H2O)2]·CH3CN (2), and [Dy2(Py3CO)2(PhCOO)4(MeOH)2]·MeOH (3), with hula-hoop-like geometries around the DyIII ions. All three complexes display slow relaxation of magnetization under a zero applied direct-current field with anisotropy barriers of 169 and 51 K for 1 and 3, respectively, while the slow relaxation of magnetization of complex 2 may mainly result from Raman relaxation. Besides, complex 1 demonstrates butterfly-type hysteresis below 4 K, and complex 2 shows no opening of the hysteresis loop with an inflection of around 0.25 T. Although complexes 2 and 3 have similar structures, the different coordinate anions induce distinct magnetic interaction states, antiferromagnetic and ferromagnetic for 2 and 3, respectively. Ab initio calculations reveal that the better SMM behavior of complex 1 should be ascribed to stronger single-ion anisotropy compared with complexes 2 and 3. The small value of the dipolar interaction results in an overall antiferromagnetic interaction for complex 2, while the large value of the dipolar interaction causes an overall ferromagnetic interaction for complex 3, where the dipolar interactions are ferromagnetic for both complexes.

A series of lanthanide complexes with 2‐fluoro‐N'‐(furan‐2‐ylmethylene) benzohydrazide ligand: Synthesis, characterization, luminescent properties and biological evaluation

Lanthanide (III) complexes were synthesized with Schiff base ligand 2‐fluoro‐N′‐(furan‐2‐ylmethylene) benzohydrazide (L). These complexes were characterized using elemental analysis, molar conductivity measurements, spectral analysis, luminescence and thermogravimetric analysis. The Schiff base ligand is a tridentate chelate and coordinates to the central lanthanide ion with 1:2 metal‐to‐ligand ratio. The conductivity data show a 1:1 electrolytic nature with general formula [LnL2(NO3)2]NO3. Eu and Tb complexes exhibit the characteristic luminescence emissions of the central metal ions attributed to efficient energy transfer from the ligand to the metal centre. Most of the complexes exhibit antibacterial activity against a number of pathogenic bacteria. Furthermore, the antioxidant activity of the ligand and its Ln (III) complexes was determined using a radical scavenging method, which indicates that the Ln (III) complexes exhibit more effective antioxidant activity than the ligand.

Electrocatalytic H2O Reduction with f-Elements: Mechanistic Insight and Overpotential Tuning in a Series of Lanthanide Complexes.

Electrocatalytic energy conversion with molecular f-element catalysts is still in an early phase of its development. We here report detailed electrochemical investigations on the recently reported trivalent lanthanide coordination complexes [((Ad,MeArO)3mes)Ln] (1-Ln), with Ln = La, Ce, Pr, Nd, Sm, Gd, Dy, Er, and Yb, which were now found to perform as active electrocatalysts for the reduction of water to dihydrogen. Reactivity studies involving complexes 1-Ln and the Ln(II) analogues [K(2.2.2-crypt)][((Ad,MeArO)3mes)Ln] (2-Ln) suggest a reaction mechanism that differs significantly from the reaction pathway found for the corresponding uranium catalyst [((Ad,MeArO)3mes)U] (1-U). While complexes 1-Ln activate water via a radical pathway, only upon a 1 e- reduction to yield the reduced species 2-Ln, the 5f analogue 1-U directly reduces H2O via a 2 e- pathway. The electrocatalytic H2O reduction by complexes 1-Ln is initiated by the respective Ln(III)/Ln(II) redox couples, which gradually turn to more positive values across the Ln series. This correlation has been exploited to tune the catalytic overpotential of water reduction by choice of the lanthanide ion. Kinetic studies of the 1-Ln series were performed to elucidate correlations between overpotential and turnover frequencies of the 4f-based electrocatalysts.

Selective and catalytic carbon dioxide and heteroallene activation mediated by cerium N-heterocyclic carbene complexes.

A series of rare earth complexes of the form Ln(LR)3 supported by bidentate ortho-aryloxide-NHC ligands are reported (LR = 2-O-3,5-tBu2-C6H2(1-C{N(CH)2N(R)})); R = iPr, tBu, Mes; Ln = Ce, Sm, Eu). The cerium complexes cleanly and quantitatively insert carbon dioxide exclusively into all three cerium carbene bonds, forming Ce(LR·CO2)3. The insertion is reversible only for the mesityl-substituted complex Ce(LMes)3. Analysis of the capacity of Ce(LR)3 to insert a range of heteroallenes that are isoelectronic with CO2 reveals the solvent and ligand size dependence of the selectivity. This is important because only the complexes capable of reversible CO2-insertion are competent catalysts for catalytic conversions of CO2. Preliminary studies show that only Ce(LMes·CO2)3 catalyses the formation of propylene carbonate from propylene oxide under 1 atm of CO2 pressure. The mono-ligand complexes can be isolated from reactions using LiCe(NiPr2)4 as a starting material; LiBr adducts [Ce(LR)(NiPr2)Br·LiBr(THF)]2 (R = Me, iPr) are reported, along with a hexanuclear N-heterocyclic dicarbene [Li2Ce3(OArCMe-H)3(NiPr2)5(THF)2]2 by-product. The analogous para-aryloxide-NHC proligand (p-LMes = 4-O-2,6-tBu2-C6H2(1-C{N(CH)2NMes}))) has been made for comparison, but the rare earth tris-ligand complexes Ln(p-LMes)3(THF)2 (Ln = Y, Ce) are too reactive for straightforward Lewis pair separated chemistry to be usefully carried out.