Anionic bipyridyl complexes of lanthanides. Structure of [Yb(bipy)3][Li(THF)4]

Reactions of Sm^II, Tb^III, Tm^II, Yb^II, and Lu^III iodides with 2,2′-bipyridyllithium in THF afford [Li(THF)₄][Ln(bipy) _n ] complexes (n=3 or 4) containing trivalent lanthanides. X-ray structural analysis demonstrated that in the crystalline state, the Yb derivative has the ionic structure, [Li(THF)₄]⁺[Yb(bipy)₃]^?. In THF solutions, the reversible ligand exchange between metal atoms occurs to yield neutral compounds [Ln(bipy) _n?1(THF) _x ] and [Li(bipy)(THF) _y ]. A decrease in the temperature shifts the equilibrium to ionic pairs.     

Rare-earth metal allyl and hydrido complexes supported by an (NNNN)-type macrocyclic ligand: synthesis, structure, and reactivity toward biomass-derived furanics

The preparation and characterization of a series of neutral rare‐earth metal complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane anion (Me₃TACD^?) are reported. Upon treatment of the neutral allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] with Brønsted acids, monocationic allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)(thf)₂][B(C₆X₅)₄] (Ln=La, Ce, Nd, X=H, F) were isolated and characterized. Hydrogenolysis gave the hydride complexes [Ln(Me₃TACD)H₂]_n (Ln=Y, n=3; La, n=4; Sm). X‐ray crystallography showed the lanthanum hydride to be tetranuclear. Reactivity studies of [Ln(Me₃TACD)R₂]_n (R=η³‐C₃H₅, n=0; R=H, n=3,4) towards furan derivatives includes hydrosilylation and deoxygenation under ring‐opening conditions.     

Basic Study of Lanthanide Nitrate Species in Solution by Electrospray Ionization Mass Spectrometry

Lanthanide nitrate (Ln(NO₃)₃) solutions were analyzed by electrospray ionization mass spectrometry (ESI-MS) to characterize the solution states of the lanthanides. The following monomer species were observed: [Ln(OH)(H₂O) _j ]²⁺, [Ln(OH)₂(H₂O) _k ]⁺, [Ln(NO₃)(OH)(H₂O) _l ]⁺ and [Ln(NO₃)₂(H₂O) _m ]⁺ (j,k,l,m: numbers of adducted H₂O). The peak intensity ratio of each Ln species was calculated from the peak intensity of the Ln species divided by the total peak intensity of all the Ln species. The change in the relative peak intensities of [Ln(OH)(H₂O) _j ]²⁺ and [Ln(OH)₂(H₂O) _k ]⁺ was consistent with changes in the hydration number of Ln (La to Tb: 9, Tb to Lu: 8). The behavior of the relative peak intensity of [Ln(NO₃)(OH)(H₂O) _l ]⁺ against the atomic number of Ln was similar to those of the stability constants of the lanthanides and the nitrate group. ESI-MS is expected to be a useful technique for examining lanthanide reactions in solution.     

Silver baits for the "miraculous draught" of amphiphilic lanthanide helicates

The axial connection of flexible thioalkyls chains of variable length (n=1–12) within the segmental bis‐tridentate 2‐benzimidazole‐8‐hydroxyquinoline ligands [ L12 ^Cn?2 H]^2? provides amphiphilic receptors designed for the synthesis of neutral dinuclear lanthanides helicates. However, the stoichiometric mixing of metals and ligands in basic media only yields intricate mixtures of poorly soluble aggregates. The addition of Ag^I in solution restores classical helicate architectures for n=3, with the quantitative formation of the discrete D₃‐symmetrical [Ln₂Ag2( L12 ^C3?2 H)₃]²⁺ complexes at millimolar concentration (Ln=La, Eu, Lu). The X‐ray crystal structure supports the formation of [La₂Ag₂( L12 ^C3?2 H)₃][OTf]₂, which exists in the solid state as infinite linear polymers bridged by S‐Ag‐S bonds. In contrast, molecular dynamics (MD) simulations in the gas phase and in solution confirm the experimental diffusion measurements, which imply the formation of discrete molecular entities in these media, in which the sulfur atoms of each lipophilic ligand are rapidly exchanged within the Ag^I coordination sphere. Turned as a predictive tool, MD suggests that this Ag^I templating effect is efficient only for n=1–3, while for n>3 very loose interactions occur between Ag^I and the thioalkyl residues. The subsequent experimental demonstration that only 25 % of the total ligand speciation contributes to the formation of [Ln₂Ag₂( L12 ^C12?2 H)₃]²⁺ in solution puts the bases for a rational approach for the design of amphiphilic helical complexes with predetermined molecular interfaces.     

Attempted Reduction of Divalent Rare Earth Iodo Aminopyridinates

Rare examples of amido‐iodo complexes of selected divalent lanthanides can be synthesized by using deprotonated Ap*H {Ap*H = 2,6‐diisopropylphenyl)‐[6‐(2,4,6‐triisopropylphenyl)‐pyridin‐2‐yl]‐amine} as a stabilizing ligand. Reaction of [Ap*K]_n with [LnI₂(thf)_n] (Ln = Eu, Yb, n = 4,5) in THF leads to [Ln(Ap*)I(thf)₂]₂ (Ln = Eu, Yb). An attempted reduction of these divalent heteroleptic complexes with KC₈ to synthesize complexes containing an unsupported Ln–Ln bond resulted in the formation of [Ln(Ap*)₂(thf)₂]. These lanthanide complexes were characterized by X‐ray structure analysis.     

Mechanism for Solvent Extraction of Lanthanides from Chloride Media by Basic Extractants

The solvent extraction of lanthanides from chloride media to an organic phase containing an anion exchanger in the chloride form is known to show low extraction percentages and small separation factors. The coordination chemistry of the lanthanides in combination with this kind of extractant is poorly understood. Previous work has mainly used solvent extraction based techniques (slope analysis, fittings of the extraction curves) to derive the extraction mechanism of lanthanides from chloride media. In this paper, EXAFS spectra, luminescence lifetimes, excitation and emission spectra, and organic phase loadings of lanthanides in dry, water-saturated and diluted Aliquat 336 chloride or Cyphos IL 101 have been measured. The data show the formation of the hydrated lanthanide ion [Ln(H₂O)_8–9]³⁺ in undiluted and diluted Aliquat 336 and the complex [LnCl₆]^3? in dry Aliquat 336. The presence of the same species [Ln(H₂O)_8–9]³⁺ in the aqueous and in the organic phase explains the small separation factors and the poor selectivities for the separation of mixtures of lanthanides. Changes in separation factors with increasing chloride concentrations can be explained by changes in stability of the lanthanide chloro complexes in the aqueous phase, in combination with the extraction of the hydrated lanthanide ion to the organic phase. Finally, it is shown that the organic phase can be loaded with 107 g·L^?1 of Nd(III) under the optimal conditions.     

Complexes of lanthanide perchlorates with 4-N-(2′-hydroxy-1′-naphthylidene)aminoantipyrine

Lanthanide perchlorate complexes with 4-N-(2′-hydroxy-1′-naphthylidene) aminoantipyrine [HNAAP(HL)] of types [Ln(L)₂ClO₄] (where Ln = La, Pr, Nd or Sm) and [Ln(HL)₄](ClO₄)₃ (where Ln = Gd, Tb, Dy, Ho or Y) have been synthesized and characterized. HNAAP acts as a monovalent terdentate ligand in the complexes of the lighter lanthanides and as a neutral bidentate ligand in the complexes of the heavier lanthanides. The perchlorate group is coordinated only in the complexes of the lighter lanthanides.     

Cationic Allyl Complexes of the Rare‐Earth Metals: Synthesis,Structural Characterization,and 1,3‐Butadiene Polymerization Catalysis

Monocationic bis‐allyl complexes [Ln(η³‐C₃H₅)₂(thf)₃]⁺[B(C₆X₅)₄]^? (Ln=Y, La, Nd; X=H, F) and dicationic mono‐allyl complexes of yttrium and the early lanthanides [Ln(η³‐C₃H₅)(thf)₆]²⁺[BPh₄]₂^? (Ln=La, Nd) were prepared by protonolysis of the tris‐allyl complexes [Ln(η³‐C₃H₅)₃(diox)] (Ln=Y, La, Ce, Pr, Nd, Sm; diox=1,4‐dioxane) isolated as a 1,4‐dioxane‐bridged dimer (Ln=Ce) or THF adducts [Ln(η³‐C₃H₅)₃(thf)₂] (Ln=Ce, Pr). Allyl abstraction from the neutral tris‐allyl complex by a Lewis acid, ER₃ (Al(CH₂SiMe₃)₃, BPh₃) gave the ion pair [Ln(η³‐C₃H₅)₂(thf)₃]⁺[ER₃(η¹‐CH₂CH?CH₂)]^? (Ln=Y, La; ER₃=Al(CH₂SiMe₃)₃, BPh₃). Benzophenone inserts into the La? C_allyl bond of [La(η³‐C₃H₅)₂(thf)₃]⁺[BPh₄]^? to form the alkoxy complex [La{OCPh₂(CH₂CH?CH₂)}₂(thf)₃]⁺[BPh₄]^?. The monocationic half‐sandwich complexes [Ln(η⁵‐C₅Me₄SiMe₃)(η³‐C₃H₅)(thf)₂]⁺[B(C₆X₅)₄]^? (Ln=Y, La; X=H, F) were synthesized from the neutral precursors [Ln(η⁵‐C₅Me₄SiMe₃)(η³‐C₃H₅)₂(thf)] by protonolysis. For 1,3‐butadiene polymerization catalysis, the yttrium‐based systems were more active than the corresponding lanthanum or neodymium homologues, giving polybutadiene with approximately 90 % 1,4‐cis stereoselectivity.     

Controlled Synthesis of Heterotrimetallic Single‐Chain Magnets from Anisotropic High‐Spin 3 d–4 f Nodes and Paramagnetic Spacers

By using the node‐and‐spacer approach in suitable solvents, four new heterotrimetallic 1D chain‐like compounds (that is, containing 3d–3d′–4f metal ions), {[Ni(L)Ln(NO₃)₂(H₂O)Fe(Tp*)(CN)₃] ? 2 CH₃CN ? CH₃OH}_n (H₂L=N,N′‐bis(3‐methoxysalicylidene)‐1,3‐diaminopropane, Tp*=hydridotris(3,5‐dimethylpyrazol‐1‐yl)borate; Ln=Gd ( 1 ), Dy ( 2 ), Tb ( 3 ), Nd ( 4 )), have been synthesized and structurally characterized. All of these compounds are made up of a neutral cyanide‐ and phenolate‐bridged heterotrimetallic chain, with a {? Fe? C?N? Ni(? O? Ln)? N?C? }_n repeat unit. Within these chains, each [(Tp*)Fe(CN)₃]^? entity binds to the Ni^II ion of the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ motif through two of its three cyanide groups in a cis mode, whereas each [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit is linked to two [(Tp*)Fe(CN)₃]^? ions through the Ni^II ion in a trans mode. In the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit, the Ni^II and Ln^III ions are bridged to one other through two phenolic oxygen atoms of the ligand (L). Compounds 1 – 4 are rare examples of 1D cyanide‐ and phenolate‐bridged 3d–3d′–4f helical chain compounds. As expected, strong ferromagnetic interactions are observed between neighboring Fe^III and Ni^II ions through a cyanide bridge and between neighboring Ni^II and Ln^III (except for Nd^III) ions through two phenolate bridges. Further magnetic studies show that all of these compounds exhibit single‐chain magnetic behavior. Compound 2 exhibits the highest effective energy barrier (58.2 K) for the reversal of magnetization in 3d/4d/5d–4f heterotrimetallic single‐chain magnets.     

Differentiable Formation of Chiroptical Lanthanide Heterometallic LnnLn’4-n(L6) (n=0–4) Tetrahedra with C2-Symmetrical Bis(tridentate) Ligands

Construction of lanthanide heterometallic complex is important for engineering multifunction molecular containers. However, it remains a challenge because of the similar ionic radii of lanthanides. Herein we attempt to prepare chiral lanthanide heterometallic tetrahedra. Upon crystallization with a mixture of [Eu₂ L ₃] and [Ln₂ L ₃] (Ln=Gd, Tb and Dy) helicates, a mixture of heterometallic Eu_nLn’_4-n( L ₆) (n=0–4) tetrahedra was prepared. Selective formation of heterometallic tetrahedron was observed as MS deconvolution results deviated from statistical results. The formation of heterometallic tetrahedron was found to be sensitive to ionic radii as well as the ratio of the two helicates used in the crystallization.     

Cyano-bridged Ln^3＋-Cr^3＋ Binuclear Complexes [Ln（L）x（H2O）y^- Cr（CN）6]·mL·nH2O （Ln=La-Nd,x=5, y=2, m=1 or 2, n=2 or 2.5; Ln-Sm-Dy,Er, x=4, y=3, m=0, n=1.5 or 2.0; L= 2-pyrrolidinone）： Structure,Magnetism and Spin Density Map

In order to shed light upon the nature and mechanism of 4f-3d magnetic exchange interactions, a series of binuclear complexes of lanthanide（3＋） and chromium（3＋） with the general formula [Ln（L）5（H2O）2Cr（CN）6]·mL· nH2O （Ln=La （1）, Ce （2）, Pr （3）, Nd （4）; x=5, y=2, m=1 or 2, n=2 or 2.5; L=2-pyrrolidinone） and [Ln（L）4（H2O）3Cr（CN）6] ·nH2O （Ln=Sm （5）, Eu （6）, Gd （7）, Tb （8）, Dy （9）, Er （10）; x=4, y=3, m=0, n= 1.5 or 2.0; L=2-pyrrolidinone） were prepared and the X-ray crystal structures of complexes 2, 6 and 7 were determined. All the compounds consist of a Ln-CN-Cr unit, in which Ln^3＋ in a square antiprism environment is bridged to an octahedral coordinated Cr^3＋ ion through a cyano group. The magnetic properties of the complexes 3 and 6-10 show an overall antiferromagnetic behavior. The fitting to the experimental magnetic susceptibilities of 7 give g= 1.98, J=0.40 cm^-1, zJ＇= -0.21 cm^-1 on the basis of a binuclear spin system （Scd=7/2, Scr=3/2）, revealing an intra-molecular Gd^3＋-Cr^3＋ ferromagnetic interaction and an inter-molecular antiferromagnetic interaction. For 7 the calculation of quantum chemical density functional theory （DFT）, combined with the broken symmetry approach, showed that the calculated spin coupling constant was 20.3 cm^-1, supporting the observation of weak ferromagnetic intra-molecular interaction in 7. The spin density distributions of 7 in both the high spin ground state and the broken symmetry state were obtained, and the spin coupling mechanism between Gd^3＋ and Cr^3＋ was discussed.     

Coordination polymers of lanthanides incorporating N,N′-ethylenebis(2-hydroxy-1-naphthylideneiminato): syntheses and crystal structures

Reaction of Ln(NO₃)₃?·?6H₂O with H₂napn (H₂napn?=?N,N′-ethylenebis(2-hydroxy-1-naphthylideneiminato)) and KSCN produces seven new coordination polymers, [La(H₂napn)(SCN)(C₂H₅OH)₂(NO₃)₂] _n (1), [La(H₂napn)₂(SCN)(NO₃)₂] _n (2), and [Ln(H₂napn)_1.5(NO₃)₃] _n [Ln?=?La(3), Sm(4), Eu(5), Dy(6), Er(7)]. Crystal structure analysis reveals that H₂napn functions as a bridging ligand, forming a 1-D chain polymer (1) and 2-D open-frameworks (2–7) with lanthanides. Each metal center of 1–7 is nine-coordinate. Lanthanide contraction is observed in 3–7.     

Synthesis,crystal structure and characterization of a series of complexes constructed from coordinated Lanthanides(III) and the heteropolyanion [SiMo12O40]4−

The reaction of α-[SiMo₁₂O₄₀]^4? with trivalent cations Ln³⁺ and N-methyl-2-pyrrolidone leads to a series of complexes of formula [Ln(NMP)₄(H₂O) _n ]H[SiMo₁₂O₄₀]?·?2NMP?·?mH₂O [where Ln?=?La (1), Pr (2), Nd (3), Sm (4), Gd (5), n?=?4, Ln?=?Dy (6), Er (7), n?=?3. NMP?=?N-methyl-2-pyrrolidone]. The syntheses, X-ray crystal structures, IR, and ESR spectra and thermal properties of the complexes 1, 2, 4, 6, 7 have been reported previously. Here, we report X-ray crystal structures, IR, UV, ESR spectra and thermal properties of the complexes [Nd(NMP)₄(H₂O)₄]H[SiMo₁₂O₄₀]?·?2NMP?·?1.5H₂O (3), and [Gd(NMP)₄(H₂O)₄]H[SiMo₁₂O₄₀]?·?2NMP?·?H₂O (5). In addition, the electrochemical behaviour of this series of complexes in aqueous solution and aqueous-organic solution has been investigated and systematic comparisons have been made. All these complexes exhibit successive reduction process of the Mo atoms.     

Darstellung und Eigenschaften von Diphthalocyaninaten des Bismuts, [Bi(Pc)2]k (k = 1−, 0, 1+); Kristallstruktur von gemischtvalentem [Bi(Pc)2] · CH2Cl2

Synthesis and Properties of Diphthalocyaninates of Bismuth, [Bi(Pc)₂]^k (k = 1?, 0, 1+); Crystal Structure of mixed-valent [Bi(Pc)₂] · CH₂Cl₂ Blue di(phthalocyaninato(2-))bismuthate(III), [Bi(Pc^2?)₂]^?, is obtained by the reaction of BiO(NO₃) with molten 1,2-dicyanobenzene in the presence of potassium methylate and isolated as tetra-n-butylammonium (ⁿBu₄N)⁺ and bis(triphenylphosphine)iminium (PNP)⁺ salt. Green mixed-valent [Bi(Pc)₂] · CH₂Cl₂ is prepared by anodic oxidation of [Bi(Pc^2?)₂]^?. It crystallizes in the orthorhombic γ modification (Pnma; a = 28.176(5), b = 22.913(3), c = 7.925(1) Å, Z = 4). The Bi^III ion is eightfold coordinated by the N_iso atoms of the slightly distorted Pc ligands in a square antiprismatic manner. The average Bi? N_iso bond distance is 2.467 Å. The complex is paramagnetic (μ_eff = 1.84 μ_B). Oxidation of [Bi(Pc^2?)₂]^? with bromine yields purple, diamagnetic [Bi(Pc^?)₂]Br_x (1.5 ≤ x ≤ 2.5). The redox properties are investigated electrochemically. UV-Vis-NIR, MIR/FIR and resonance Raman spectra of the new bismuth(III) complexes are discussed and compared with those of diphthalocyaninates of the lanthanides.     

Mixed-ligand lanthanide complexes constructed by flexible 1,3-propanediaminetetraacetate and rigid terephthalate

Abstract

Coordination polymers (CPs) of mixed-ligand lanthanide complexes [Ln₂(1,3-pdta)(TPA)(H₂O)₂]_n·nH₂O [Ln?=?La, 1; Ce, 2; Pr, 3; Nd, 4] (1,3-H₄pdta = 1,3-propanediaminetetraacetic acid; H₂TPA?= terephthalic acid) were hydrothermally synthesized with flexible 1,3-pdta and rigid TPA ligands. Moreover, lanthanide propanediaminetetraacetates [Ln(1,3-Hpdta)(H₂O)]_2n·nH₂TPA·xH₂O [Ln?=?Sm, 5; Gd, 6] with multi-layered structures were also obtained. In 1–4, both 1,3-pdta and TPA coordinate with lanthanide ions through carboxyl oxygen and nitrogen atoms. In 5 and 6, only 1,3-Hpdta coordinates with the central lanthanide ion, where one nitrogen atom in 1,3-Hpdta is protonated, and TPAs are crystallized as H₂TPA with the central multi-layered structures of [Ln(1,3-Hpdta)(H₂O)]_2n through very strong hydrogen bonds [2.504(4) Å]. Solid-state ¹³C NMR analysis of 1 revealed the coordination of carboxyl groups. However, the methylene groups of 1,3-pdta showed an obvious upfield shift, which can be attributed to the effects of the phenyl ring in TPA ligand. The successful synthesis of these mixed-ligand lanthanides provides a rational design of such lanthanide CPs with flexible and rigid ligands.     

Palladium- and platinum-containing free radicals

The synthesis and ESR-spectra of the novel paramagnetic σ-phenoxyl derivatives L₂M[C₆H₂-t-Bu₂O^?]X (M = Pd, Pt; L = PPh₃; X = Cl) are reported.     

Tetrathiafulvalene‐amido‐2‐pyridine‐N‐oxide as Efficient Charge‐Transfer Antenna Ligand for the Sensitization of YbIII Luminescence in a Series of Lanthanide Paramagnetic Coordination Complexes

The tetrathiafulvalene‐amido‐2‐pyridine‐N‐oxide ( L ) ligand has been employed to coordinate 4f elements. The architecture of the complexes mainly depends on the ionic radii of the lanthanides. Thus, the reaction of L in the same experimental protocol leads to three different molecular structure series. Binuclear [Ln₂(hfac)₅(O₂CPhCl)( L )₃] ? 2 H₂O (hfac^?=1,1,1,5,5,5‐hexafluoroacetylacetonate anion, O₂CPhCl^?=3‐chlorobenzoate anion) and mononuclear [Ln(hfac)₃( L )₂] complexes were obtained by using rare‐earth ions with either large (Ln^III=Pr, Gd) or small (Ln^III=Y, Yb) ionic radius, respectively, whereas the use of Tb^III that possesses an intermediate ionic radius led to the formation of a binuclear complex of formula [Tb₂(hfac)₄(O₂CPhCl)₂( L )₂]. Antiferromagnetic interactions have been observed in the three dinuclear compounds by using an extended empirical method. Photophysical properties of the coordination complexes have been studied by solid‐state absorption spectroscopy, whereas time‐dependent density functional theory (TD‐DFT) calculations have been carried out on the diamagnetic Y^III derivative to build a molecular orbital diagram and to reproduce the absorption spectrum. For the [Yb(hfac)₃( L )₂] complex, the excitation at 19 600 cm^?1 of the HOMO→LUMO+1/LUMO+2 charge‐transfer transition induces both line‐shape emissions in the near‐IR spectral range assigned to the ²F_5/2→²F_7/2 (9860 cm^?1) ytterbium‐centered transition and a residual charge‐transfer emission around 13 150 cm^?1. An efficient antenna effect that proceeds through energy transfer from the singlet excited state of the tetrathiafulvalene‐amido‐2‐pyridine‐N‐oxide chromophore is evidence of the Yb^III sensitization.     

Intra‐ and Intermolecular Dispersion Interactions in [n]Cycloparaphenylenes: Do They Influence Their Structural and Electronic Properties?

Cycloparaphenylenes (CPPs) are nanosized structures with unique isolated and bulk properties, and are synthetic targets for the template‐driven bottom‐up synthesis of carbon nanotubes. Thus, a systematic understanding of the supramolecular order at the nanoscale is of utmost relevance for molecular engineering. In this study, it is found that intramolecular noncovalent (dispersion) interactions must be taken into account for obtaining accurate estimates of the structural and optoelectronic properties of [n]CPP compounds, and their influence as the number of repeat units increases from n=4 to n=12 is also analyzed, both in the gas phase and in solution. The supramolecular self‐assembly, for which both intra‐ and intermolecular noncovalent interactions are relevant, of [6]CPP is also investigated by calculating the binding energies of dimers taken along several crystal directions. These are also used to estimate the cohesive energy of the crystal, which is compared to the value obtained by means of dispersion‐corrected DFT calculations using periodic boundary conditions. The reasonable agreement between both computational strategies points towards a first estimate of the [6]CPP cohesive energy of around 50 kcal mol^?1.     

Structure and Properties of Heterometallics Based on Lanthanides and Transition Metals with Methoxy-β-Diketonates

The possibility of obtaining volatile polynuclear heterometallic complexes containing lanthanides and transition metals bound by methoxy-β-diketonates was studied. New compounds were prepared by cocrystallization of monometallic complexes from organic solvents. Ln(tmhd)₃ were used as initial monometallic complexes (Ln = La, Pr, Sm, Gd, Tb, Dy, Lu; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate) in combination with TML₂ in various ratios (TM = Cu, Co, Ni, Mn; L: L¹ = 1,1,1-trifluoro-5,5-dimethoxypentane-2,4-dionate, L² = 1,1,1-trifluoro-5,5-dimethoxy-hexane-2,4-dionate, L³ = 1,1,1-trifluoro-5-methoxy-5-methylhexane-2,4-dionate). Heterometallic complexes of the composition [(LnL₂tmhd)₂TM(tmhd)₂] were isolated for light lanthanides Ln= La, Pr, Sm, Gd, and L= L¹ or L². By single crystal XRD, it has been established that heterometallic compounds containing La, Pr, Cu, Co, and Ni are isostructural linear coordination polymers of alternating mononuclear transition metal complexes and binuclear heteroleptic lanthanide complexes, connected by donor–acceptor interactions between oxygen atoms of the methoxy groups and transition metal atoms. A comparison of powder XRD patterns has shown that all heterometallic complexes obtained are isostructural. Havier lanthanides Ln = Tb, Dy, Lu did not form heterometallics. Instead, homometallic complexes Ln(L³)₃ were identified for Ln = Dy, Lu as well as for Ln = La. The thermal properties of the complexes were investigated by TG-DTA and vacuum sublimation tests. The heterometallic complexes were found to be not volatile and decomposed under heating to produce inorganic composites of TM oxides and Ln fluorides. In contrast, Ln(L³)₃ is volatile and may be sublimed in a vacuum. Results of magnetic measurements are discussed for several heterometallic and homometallic complexes.     

Molecular Magnetism and Iron(II) Spin-State Equilibrium as Structural Probes in Heterodinuclear d–f Complexes

Fe(ClO₄)₂ reacts with the segmental ligand 2-{6-[1-(3,5-dimethoxybenzyl)-1H-benzimidazol-2-yl]pyridin-2-yl}-1,1′-dimethyl-5,5′-methylene-2′-(5-methylpyridin-2-yl)bis[1H-benzimidazole] ( L ²) in MeCN to give the diamagnetic deep violet complex [Fe( L ²)₂]²⁺ where the metal is pseudo-octahedrally coordinated by two perpendicular tridentate binding units. When L ² reacts with an equimolar mixture of Ln(ClO₄)₃ (Ln = La, Ce, Pr, Nd, Sm, Eu) and Fe(ClO₄)₂, electrospray-mass spectrometric, spectrophotometric, and ¹H-NMR data in MeCN show the selective formation of the deep red heterodinuclear C₃-cylindrical complexes [LnFe( L ²)₃]⁵⁺ where the three ligands L ² are wrapped about the metal-metal axis. Fe^II occupies the pseudo-octahedral capping site produced by the three bidentate units and Ln^III lies in the resulting ‘facial’ pseudo-tricapped trigonal prismatic site defined by the three remaining tridentate coordinating units. The heterodinuclear complexes [LnFe( L ²)₃]⁵⁺ display spin-state equilibrium (¹A ? ⁵T) and thermochromism in MeCN between 243 and 333 K. Detailed ¹H-NMR, UV/VIS, and magnetic measurements in solution show that the partial spin-crossover behavior of [LnFe( L ²)₃]⁵⁺ occurs for Ln = La? Eu with similar thermodynamic parameters (ΔH_sc = 20–23 kJ·mol^?1 and ΔS_sc = 55–66 J·mol^?1·K^?1) indicating that the size of Ln^III has a negligible influence on the spin-state equilibrium. However, the smaller Ln^III ions have less affinity for the pseudo-tricapped trigonal prismatic coordination site in the heterodinuclear complexes as demonstrated by the partial decomplexation of [YFe( L ²)₃]⁵⁺ to give [Fe( L ²)₂]²⁺ and the absence of the heterodinuclear complex [LuFe( L ²)₃]⁵⁺ under the same conditions. The crucial role played by the sterically demanding Fe^II in the assembly processes is discussed together with the use of the efficient combination of lanthanide probes with magnetic d-block probes for the design and investigation of luminescent and magnetic materials with controlled structural and physical properties. Photophysical measurements reveal that efficient ligand → metal and Eu → Fe energy transfer occur in [EuFe( L ²)₃]⁵⁺ which strongly quench both the ligand and the Eu-centered luminescence.