Ln Coordination Research Articles

Influence of Aqueous Phase Acidity on Ln(III) Coordination by N,N,N',N'-Tetraoctyldiglycolamide.

This study highlights the importance of combining distribution ratio measurements with multiple spectroscopic techniques to provide a more comprehensive understanding of organic phase Ln coordination chemistry. Solvent extraction investigations with N,N,N',N'-tetraoctyldiglycolamide (TODGA) in n-heptane reveal the sensitivity of Ln complexation to the HNO3 concentration. Distribution ratio measurements in tandem with UV-Vis demonstrated that increasing the concentration of HNO3 above 0.5 M with a constant NO3- of 1 M increases the number of coordinating TODGA molecules, from a 1:2 to a 1:3 Ln:TODGA complex. At each concentration of HNO3 considered herein (from 0.01 to 1 M), Eu lifetime analysis demonstrated no evidence of H2O coordination. Results from Fourier transform infrared investigations suggest the presence of inner-sphere NO3- under low concentrations of HNO3 when the 1:2 Ln:TODGA complex is present. Increasing the HNO3 concentration above 0.5 M increases the propensity for outer-sphere interactions by removing the coordinated NO3- and saturating the Ln coordination sphere with three TODGA molecules, resulting in the well-established cationic, trischelate homoleptic [Ln(TODGA)3]3+ complex. This work demonstrates the importance in considering the NO3- source for solvent extraction systems. In particular, for systems with an affinity for outer-sphere interactions with molar concentrations of HNO3, changing the NO3- source can change the inner-sphere coordination of the Ln complex, which, in turn, affects the separation efficacy.

A Family of Lanthanoid‐Sodium Multifunctional Coordination Polymers: Single‐Molecule Magnet, Luminescent and Magnetocaloric Properties

AbstractIn this paper we report the microwave assisted synthesis and characterization of a family of Na−Ln coordination polymers (CPs) of formula [NaDy2(MeCOO)2(SALOH)5(chpH)2] (1Ln, Ln=Eu, Gd, Tb, Dy, Ho, Y). The Na+ cations isolate Ln2 units in a one‐dimensional polymer. By changing the lanthanoid ions, we attain Single Molecule Magnet properties (1Dy), luminescent properties (1Eu, 1Tb, 1Ho), a diamagnetic material (1Y) and a material that presents magnetocaloric effect (1Gd).

It's not just the size that matters: crystal engineering of lanthanide-based coordination polymers.

Synthesis and characterization of Lewis base free coordination polymers of selected lanthanides are presented. For this purpose, the substituted CotTIPS ligand (CotTIPS = 1,4-bis-triisopropylsilyl-cyclo-octatetraendiide) was used to synthesize homoleptic, anionic multidecker compounds of the type [K{LnIII(ɳ8-CotTIPS)2}]n. Depending on the solvent used for crystallization and the ionic radii of the lanthanide cations, three different categories of one-dimensional heterobimetallic coordination polymers were obtained in the solid state. For the early lanthanides La and Ce a unique helical conformation was obtained by crystallization from toluene, while the ionic radius of Pr seems to be a turning point towards the crystallization of zigzag polymers. For Er a third structural motif, a trapezoidal wave polymer was observed. Additionally, the zigzag polymer for all compounds could be obtained by changing the solvent from toluene to Et2O, reavealing a correlation between solid-state structure and ionic radii as well as solvent. While photoluminescence (PL) properties of Cot-lanthanide compounds are scarce, the La complexes show ligand centered green luminescence, whereas the Ce complexes reveal deep red emission origin from d-f transitions. The Er-compounds are single-molecule magnets, in which the magnetic relaxation of each Er ion occurs isolated from its neighbors at temperatures above 10 K, while below 9 K a strong antiferromagnetic coupling between the Er ions was seen.

Syntheses, structures and photophysical properties of Ni/Co[sbnd]Ln coordination polymers

The new Ni/Co-Ln coordination polymers (CPs), {[LnNi0.5(2,5-pydc)(ox)(H2O)x]·yH2O}n (Ln = Pr 1, Nd 2, x = 4, y = 2; Gd 3, Tb 4, Dy 5, x = 3, y = 1; 2,5-H2pydc = pyridine-2,5-dicarboxylic acid, H2ox = oxalic acid); {[Er2Ni(2,5-pydc)3(ox)(H2O)4]·2H2O}n6; {[LnCo0.5(2,5-pydc)(ox)(H2O)x]·yH2O}n (Ln = Pr 7, Nd 8, x = 4, y = 2; Tb 9, x = 3, y = 5) were successfully synthesized by the hydrothermal methods, and their crystal structures were characterized by single-crystal X-ray diffraction. With the participation of the auxiliary ligands (ox2−), the main ligands (2,5-pydc2−) adopt four coordination modes and make these polymers exhibit three kinds of crystal structures. CPs 1, 2, 7 and 8 are isomorphous and exhibit 2D layers which are further connected to form the 3D structure by hydrogen bonds. The other four CPs are bridged into the 3D network structure by 2,5-pydc2- and ox2−. All the polymers are characterized by IR spectro, Roman spectro, thermogravimetric analysis and X-ray powder diffraction. The UV–vis–NIR absorption spectra and Vis fluorescence excitation and emission spectra of nine coordination polymers are measured and analyzed. All the CPs show ligand-to-metal charge transfer (LMCT) transition emission of NiII/CoII–ligands, while some of the CPs show weak characteristic luminescence of LnIII ions.

A new Ln(III) coordination polymer constructed from a hexadentate triazine ligand: Treatment activity and nursing value for ovarian cancer

In this current paper, a 3D lanthanide (Ln) coordination polymer (CP), compound 1 with a chemical formula of [(NH 2 (Me) 2 )] 6 ·[Gd 3 (TATAT) 2 (μ 2 -O) 1.5 ]·3EtOH·7.5H 2 O is synthesized with the reaction between GdCl 3 ·6H 2 O and 5,5′,5′′-(1,3,5-triazine-2,4,6-triyltriimino)tris(azanediyl) triisophthalate (H 6 TATAT). Its treatment activity and nursing value against ovarian cancer is tested and the associated mechanism is analyzed simultaneously. At first, the CCK-8 detection is implemented to determine the suppression activity of compound 1 against the cell viability of ovarian cancer after treated via our compound. Furthermore, in order to detect the relative expression for the estrogen receptor on cells of ovarian cancer, real time RT-PCR is carried out.

Structures, fluorescence, and superoxide radical scavenging activities of two cd–Ln (Ln = Gd, Er) coordination polymers with an open-chain ether Schiff base and isonicotinate

Two Cd–Ln coordination polymers (CPs), with the open-chain ether Schiff base bis(5-bromine-3-methoxysalicylidene)-3-oxapentane-1,5-diamine (H2L), {[CdLnL(OAc)(NO3)(CH3OH)(isonicotinate)]·(3CH2Cl2)}n (Ln = Gd (1) and Er (2)), have been synthesized by the interfacial diffusion method. The structure analysis reveals that both CPs 1 and 2 are infinite one-dimensional zigzag coordination polymers, which are formed by isonicotinate bridging CdLnL cluster units. The fluorescence properties of H2L, 1 and 2 in the solid-state were studied. Compared with the free H2L, the fluorescence peaks of the two Cd–Ln CPs have undergone a significant blue shift (about 80 nm) and enhancement. This is due to the increased rigidity of the ligand after coordination of the metal ions with the ligand, which reduces the energy loss of thermal vibration. The fluorescence enhancement of 1 is greater than that of 2, which may be caused by the lanthanide contraction. Moreover, the results of experiments in vitro indicate that H2L, 1 and 2 have good ability to scavenge superoxide radical and that 1 and 2 are higher than free H2L, where their IC50 value is in the range 12.5–21.4 μM.

Heteroleptic lanthanide(III) complexes: synthetic utility and versatility of the unsubstituted bis-scorpionate ligand framework

The unsubstituted bis-hydrotris(1-pyrazolyl)borate) (Tp) ligand framework has been used to synthesise a range of heteroleptic Ln(III) coordination complexes [Ln(Tp)2(X)]. The precursor complexes [Ln(Tp)2(OTf)] 1-Ln (Ln = Y, Eu, Gd, Yb; OTf = triflate) were synthesised by reaction of Ln(OTf)3 with two equivalents of K(Tp). The 8-coordinate β-diketonate complexes [Ln(Tp)2(hfac)] 2-Ln (Ln = Y, Eu, Yb; hfac = hexafluoroacetylacetonate) were synthesised from Ln(OTf)3 by reacting 1-Ln generated in situ with an equivalent of K(hfac). The 7-coordinate amide complexes [Ln(Tp)2(N″)] 3-Ln (Ln = Y, Yb; N″ = bis(trimethylsilyl)amide) were synthesised from 1-Ln by reaction with K(N″). Reactivity of 3-Ln towards protonolysis was demonstrated by the isolation of the hydroxide dimer [{Y(Tp)2(μ-OH)}2] 4-Y from adventitious reaction with water and the aryloxide complex [Ln(Tp)2(OAr)] 5-Ln (Ln = Y, Yb; OAr = 2,6-tBu2-4-Me-phenoxide) from reaction with H(OAr). Full characterisation data are presented for all complexes, including solid-state molecular structure determination by single-crystal X-ray diffraction.

Seven Ln(III) coordination polymers with two kinds of geometric coordination but the same 3D topological property: luminescence sensing and magnetic property.

Two series of seven lanthanide metal coordination polymers (Ln-CPs) formulated as {[Ln(dttpa)1.5(H2O)2]·H2O}n [Ln = La3+ (1), Ce3+ (2), Nd3+ (3), Sm3+ (4) and Eu3+ (5)] and {[Ln (dttpa)1.5(H2O)]·xH2O}n [Ln = Tb3+ (6) and Er3+ (7), x = 0.75] have been successfully constructed using Ln3+ ions and 2,5-di(1H-1,2,4-triazol-1-yl)terephthalic acid (H2dttpa) via a hydrothermal method. Their 3D structures are fully characterised by Fourier transform infrared (FT-IR) spectroscopy, X-ray single-crystal analyses, powder diffraction analyses (PXRD), elemental analyses (EAs) and thermogravimetric analyses (TGAs). All Ln-CPs display the same topological property with the point symbol of {42·84}{44·62}2{49·66}2, and crystallize in the triclinic space group P1̄. Interestingly, Eu-CP (5) effectively sensitizes the visible emission of Tb3+ and shows high selectivity and stable response with the lowest detection limit of 9.88 nM. Furthermore, Tb-CP (6) acts as a good luminescence sensor to detect nitrobenzene (NB) with a detection limit of 12.5 nM. In addition, the magnetic susceptibility measurement for Er-CP (7) further shows that compounds constructed by dttpa2- are a kind of promising functional material.

SEARCH FOR WAYS OF CONTROLLED MODIFICATION OF CHARACTERISTICS OF FUNCTIONAL UNITS OF ADAPTIVE AIR PURIFICATION SYSTEMS

Information on alkaline coordination nitrates of rare-earth elements of the cerium subgroup - precursors of promising modern multifunctional materials - on the conditions of their formation and existence, the nature of the chemical bond, the composition, structure, shape of the Ln coordination polyhedra, the type of ligand coordination, and the existence of isotypic series in stoichiometry are generalized. composition, structure, characteristic properties. The data obtained (as primary information) is the basis for the detection, identification, and control of the phase state of processing objects in the preparatory stages, the choice of criteria for the compatibility of the components in the formation of single-layer and layered nanostructured oxide composite systems of lanthanides and transition elements for general purposes, with catalytic and photocatalytic activity, coatings self-cleaning with hydrophilic properties; development of various combined methods for their activation and identification of technological functional dependencies; controlled modification of the properties of the obtained target products. To increase the photocatalytic activity of coating samples based on highly dispersed anatase TiO2, a methodology for chemical modification of oxidation centers in their surface layer with heat treatment in contact with thermolysis products of alkaline coordination lanthanide nitrate melts is proposed. An effective test photocatalytic destruction of organic substrates vapors has been discovered using ethanol as an example.Effective activation of the functioning of functional units in the composition of self-adjusting air purification complexes using new photocatalytically active three-layer perovskite-like oxide materials M2Ln2Ti3O10 (M - Li, Na, K; Ln - La, Nd) has been proven. The variability of such methods for creating and modifying the characteristics of polyfunctional coatings is determined by the number and individual properties of representatives of the natural series of lanthanides, alkali metals of the periodic system, the peculiarities of their cooperative behavior in the preparatory technological stages, conditions and methods of activation of formation processes, the nature of the substrate, and other factors.

STRUCTURE AND SPECTRAL-LUMUINESCENT PROPERTIES OF LANTHANIDE-CONTAINING COMPLEXES WITH AZACROWN CALIXARENES

Lanthanide complexes with calix[4]arenes lower rim substituted with two azacrown ether fragments are reported. The size of the substituent cavity varied from 4 to 6 heteroatoms. The complexes were analyzed by means of IR, NMR, ESI mass spectroscopy. It is assumed that the coordination of Ln(III) ions occurs through the donor atoms of the lower rim; the counter anion and solvent molecule are also coordinated. Lanthanide-centered characteristic luminescence was observed in Eu(III), Tb(III) and Yb(III) complexes. The most efficient 4f-luminescence is observed for terbium-containing complexes with benzo-crown-derived ligands. The pathways of the sensitization of 4f-luminescence are discussed.

Syntheses, structures and luminescent properties of a series of Ln(III) coordination polymers

Seven coordination polymers having the general formula {[Ln2(2,6-pydc)(ox)2⋅(H2O)4]⋅3H2O}n (Ln = Sm 1, Eu 2, Gd 3, Tb 4, Dy 5, Ho 6, Er 7; 2,6-pydc2− = 2,6-pyridinedicarboxylate, ox2− = oxalate) were synthesized by the hydrothermal method. Their IR, UV-Vis-NIR absorption spectra, and Vis-NIR emission spectra were investigated, and the luminescent properties of the polymers were studied in detail. Crystal structures were determined by means of a single-crystal X-ray diffractometer, and all of them proved to have three-dimensional frameworks. Except for polymers 3 and 7, the polymers displayed the characteristic emissions of Ln(III) ions due to the effective sensitization of ligands. At the same time, the 4f orbitals of Ln(III) ions were shifted by the effects of ligand field, which influenced emission spectra and absorption spectra of some of the polymers.

Strong circularly polarized luminescence of mixed lanthanide coordination polymers with control of 4f electronic structures.

This paper reports chiral mixed Eu(iii)-Ln(iii) coordination polymers (Ln = Gd and Sm) with a high dissymmetry factor of circularly polarized luminescence (gCPL = 0.15) for the enhancement of the emission quantum yield (Φtot ≥ 50%), achieved via control of 4f electronic structures.

Synthesis, Structures and Properties of Two Ln(III) Coordination Polymers based on Pyrimidine‐2‐carboxylic Acid and Sodium Dicyanamide

AbstractAssemblies of pyrimidine‐2‐carboxylic acid (Hpmc) and samarium nitrate or europium nitrate in the presence of sodium dicyanamide (Na‐dca) under ambient conditions yielded two new coordination polymers, namely [Ln(pmc)2(dca)(H2O)2]n (Ln=Sm (1), Eu (2)). The complexes were characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR and fluorescence spectra. Structure analysis shows two complexes are isostructural with monoclinic (C2/c) symmetry. And each central metal atom is coordinated by three chelate pmc−, one terminal dca− and two water molecules to generate an infinite zigzag chain. Through Owater−H ⋅ ⋅ ⋅ Ocarboxylate, Owater−H ⋅ ⋅ ⋅ Npyrimidine hydrogen bonds, the chains are connected to a two‐dimensional net, which is furtherly extended to a three‐dimensional supramolecular structure by Owater−H ⋅ ⋅ ⋅ Ncyano hydrogen bonds. Luminescent measurement of complex 2 shows the characteristic fluorescence of Eu3+.

Peculiarities of transformations in systems of coordination of nitrate precursors of REE and alkali metals during formation of polyfunctional photocatalytically active layered oxide materials

The information on alkaline coordination nitrates of rare-earth elements of the cerium subgroup – precursors of promising modern multifunctional materials – on the conditions of their formation and existence, nature of chemical bonding, composition, structure, shape of Ln coordination polyhedra, type of ligand coordination, existence of isotype series is generalized. on stoichiometry of structure, structure, the found out characteristic properties. The obtained data (as primary information) are the basis for detection, identification, control of the phase state of processing objects in the preparatory stages, selection of compatibility criteria of components in the formation of single-layer and layered nanostructured oxide composite systems of lanthanides and transition elements with catalytic activity and photocatalyst., a coating capable of self-cleaning with hydrophilic properties; development of various combined methods of their activation and establishment of technological and functional dependencies; controlled modification of the properties of the obtained target products. To increase the photocatalytic activity of coating samples based on highly dispersed TiO2 anatase modification, a methodology for chemical modification of oxidation centers in their surface layer with heat treatment in contact with thermolysis products of alkaline coordination nitrates of lanthanides is proposed. The effective test photocatalytic destruction of vapors of organic substrates on the example of ethanol is revealed.

Structural Complexity and Magnetic Orderings in a Large Family of 3d–4f Heterobimetallic Sulfates

The synthesis of a large family of heterobimetallic lanthanide copper sulfates was realized via stoichiometric hydrothermal reactions among Ln2O3, CuO, and H2SO4, giving rise to four distinct phases, namely Ln2Cu(SO4)2(OH)4 (Ln = Sm-Ho) (LnCuSO4-1), Ln4Cu(SO4)2(OH)10 (Ln = Tm-Lu) (LnCuSO4-2), LnCu(SO4)(OH)3 (Ln = Nd-Gd, except Pm) (LnCuSO4-3), and LnCu(SO4)(OH)3 (Ln = Dy-Lu) (LnCuSO4-4), with completely different topologies. The passage from LnCuSO4-1 and LnCuSO4-3 to LnCuSO4-2 and LnCuSO4-4 across the 4f series, respectively, can be ascribed to the effect of lanthanide contraction, which progressively induces shrinking of the Ln-O distance, reduction in the Ln coordination number, and eventually structural transitions. The incorporation of identical 3d-4f metal ions into different spin-lattices, in conjunction with substitution of diverse Ln3+ cations within the same spin-lattice, gives rise to tunable magnetic properties varying from ferromagnetic ordering in GdCuSO4-3 and HoCuSO4-4 to antiferromagnetic ordering in YbCuSO4-4, and to paramagnetic correlations found in GdCuSO4-1 and YbCuSO4-2.

Ligand architectural effect on coordination, bonding, interaction, and selectivity of Am(iii) and Ln(iii) ions with bitopic ligands: synthesis, solvent extraction, and DFT studies.

The isolation of Am(iii) ion from Ln(iii) ions is very crucial for the safe disposal of nuclear wastes and thus, studies are being continuously pursued to accomplish this goal. In view of this, herein, a new conformationally rigid bitopic ligand, N,N,N',N'-tetra(2-ethylhexyl)piperazine-di-methylenecarboxamide (PIPDA) has been synthesized and studied for the separation of Am(iii) from Ln(iii) ions. The effect of structural rigidification on the selectivity of Am(iii) over Ln(iii) was compared with an open chain flexible compound, namely, N,N,N',N'-tetra(2-ethylhexyl)-3,6-(N'',N'''-dibutyl)diaza-octane-1,8-diamide (DADA). Two oxygen atoms of the diamide moiety seem to be responsible for controlling the metal ion extraction ability of PIPDA, whereas two nitrogen atoms of the piperazine moiety most probably dictate the separation factor between the Am(iii) and Eu(iii) ions in PIPDA. In addition, scalar relativistic density functional theory (DFT) in conjunction with Born-Haber thermodynamics was used herein to compliment the experimental selectivity. The experimentally observed preferential selectivity of PIPDA for Am(iii) ion over the Ln(iii) ion was corroborated by the computed extraction free energy, ΔGext. The covalent nature of bonding between the metal ions and the ligand was confirmed by analyzing the Mayer bond order and bond character analysis using the atom in molecule concept. Though the conformational rigidity of PIPDA gives stronger interaction than DADA, it does not offer a significant advantage over DADA in terms of the separation factor. The marginal increase in the separation factor for PIPDA over DADA might be attributed to the piperazine nitrogen and to the ligand architecture during complex formation.

Excited state energy transfer from terminal β-diketonate ligands to a central boron dipyrrin (Bodipy), mediated by lanthanide (III) metals

A new boron-dipyrromethene (Bodipy) dye with phenanthro-fused groups at the β-pyrrole positions is described. The π-extended pyrrole units result in intense red-shifted absorption and emission in the visible region of the spectrum. The phenathroline groups are incorporated to allow for coordination of Ln(III) β-diketonates giving the first examples of bis-Ln(III)-Bodipy complexes (where Ln = Eu and Tb). Electronic spectroscopy of the disubstituted Ln(III)-Bodipy complexes reveal β-diketonate charge transfer in the ultraviolet region of the spectrum and π π * transitions associated with the Bodipy core. Upon excitation of the terminal antenna β-diketonate ligands, within the ultraviolet region, emission of the Bodipy core is observed with no evidence of Ln(III) emission; suggesting energy transfer from the antenna ligands to the lanthanide ion to the Bodipy core (An → Ln(III) → Bodipy).

Nitrilotris(methylenephosphonic) Complexes of Lanthanides [Na(H2O)x]2[LnIIINa6H(H2O)10{N(CH2PO3)3}2] · nH2O (LnIII = Pr, Nd)

The sodium salts of lanthanide nitrilotris(mehylenephosphonate) complexes [Na(H2O)x]2[LnIIINa6H(H2O)10{N(CH2PO3)3}2] · nH2O, where LnIII = Pr (I), and Nd (II), were prepared, isolated, and studied. The isostructural crystals are monoclinic, space group P21/c, Z = 2; for complex I, a = 11.8168(7), b = 10.5403(9), c = 19.8094(10) A, β = 94.232(5)°; for complex II, a = 11.7999(2), b = 10.5495(2), c = 19.7976(3) A, β = 94.158(2)°. The lanthanide ions are coordinated at the center of a cage consisting of two {N(CH2PO3)3} acid residues and six sodium ions, which form P–O–Na–O–P bridges. The Ln coordination polyhedron is a regular rhombohedron (CIF files CCDC nos. 1825702 (I), 1825700 (II)).

Strong Fluorescent Lanthanide Salen Complexes: Photophysical Properties, Excited-State Dynamics, and Bioimaging.

The synthesis, excited-state dynamics, and biological application of luminescent lanthanide salen complexes (Ln = Lu, Gd, Eu, Yb, salen = N, N'-bis(salicylidene)ethylenediamine-based ligands) with sandwich structures are described. Among them, Lu(III) complexes show unusually strong ligand-centered fluorescence with quantum yields up to 62%, although the metal center is close to a chromophore ligand. The excited-state dynamic studies including ultrafast spectroscopy for Ln-salen complexes revealed that their excited states are solely dependent on the salen ligands and the ISC rates are slow (108-109 s-1). Importantly, time-dependent density functional theory calculations attribute the low energy transfer efficiency to the weak spin-orbital coupling (SOC) between the singlet and triplet excited states. More importantly, Lu-salen has been applied as a molecular platform to construct fluorescence probes with organelle specificity in living cell imaging, which demonstrates the advantages of the sandwich structures as being capable of preventing intramolecular metal-ligand interactions and behaviors different from those of the previously reported Zn-salens. Most importantly, the preliminary study for in vivo imaging using a mouse model demonstrated the potential application of Ln coordination complexes in therapeutic and diagnostic bioimaging beyond living cells or in vitro.

Cationic bipy induced the three dimensional supramolecules based on azoxybenzene tetracarboxylate: Structures and NIR luminescence property

Series of Ln(III) coordination polymers, namely, {[Ln(Oaobtc)(H2O)4]·Hbipy·H2O}n(H4Oaobtc = oxidation azoxybenzene - 2, 2′, 3, 3′-tetracarboxylic acid, bipy = 4,4′-bipyridine, and Ln = Pr(1), Nd(2), Ho(3), Er(4), Yb(5), respectively) have been designed, afforded and luminescence characterized systematically. The family coordination polymers are nearly isostructural sets, featuring one dimensional (1D) zigzag double chain edifice structure, with cationic Hbipy+ guest being located along two sides. These 1D chains are interlinked into 2D network, and are further extended into 3D supramolecular architecture through hydrogen bonding interactions from the cationic Hbipy+ moiety. The photo luminescence emission spectra of polymer 1 and 4 are based on the H4aobtc acid ligand, while 2, 3 and 5 display the emissions originated from characteristic f-f transitions of Ln(III) ions within near-infrared (NIR) regions.