Synthesis,spectral characterization,thermal, computational and antibacterial studies of lanthanide complexes with 2-fluorobenzoic acid-(5-R-2-hydroxy-benzylidene)hydrazide {R = chloro or bromo)

Tridentate Schiff base ligands, 2-Fluorobenzoic acid-(5-chloro-2-hydroxy benzylidene)hydrazide {H₂L_Cl} and 2-Fluorobenzoic acid-(5-bromo-2-hydroxybenzylidene)hydrazide {H₂L_Br} have been used to prepare a variety of lanthanide complexes [HNEt₃][LnL_x(NO₃)₂(H₂O)]H₂O, Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er. The ¹H and ¹³C NMR of lanthanum in conjunction with the infrared, elemental, thermal, molecular mass and conductance measurements enable the assignment of the formula to these complexes. The anionic unit [LnL_x(NO₃)₂(H₂O)]^? contains one tridentate ONO-donor, L^2?, which coordinates the metal ions via the phenolate-O, the imine-N and the deprotonated amide-O atoms in enol tautomeric form. The coordination environment around central metal ion is completed by two bidentate nitrate ligands and one coordinated water molecule to give a coordination number of eight for Ln(III). In order to get a better insight into the structural features of the complexes, their molecular geometries were fully optimized using density functional theory calculations at the M06-2X/6-31G¹ level of theory. The antibacterial activity results, on a panel of six different bacterial strains, show that the activity of the complexes is higher than that of the free ligands and in some cases higher than that of amoxicillin which is taken as standard reference drug. Compared to the free ligands, the emission spectra of the complexes exhibit a blue-shift with a clear enhancement in the emission intensity.     

Two 2-D lanthanide coordination polymers constructed from hydroquinone-O,O′-diacetic acid

Two new coordination polymers, {Ln₂(hqda)₃(H₂O)₄·6H₂O}_n (H₂hqda = hydroquinone-O,O′-diacetic acid, Ln = Dy, 1; Ho, 2), were prepared and characterized by elemental analysis, IR spectroscopy, TG-DTA, fluorescence spectroscopy, and single-crystal X-ray diffraction. The two complexes are isomorphous with similar crystal structures. In 1 and 2, each Ln(III) ion is nine coordinate with seven oxygen atoms from hqda ligands and two oxygen atoms from water molecules. Two adjacent Ln(III) ions are bridged by–COO^? groups from hqda ligands in bidentate-bridging and chelating-bridging modes. These building blocks cross link through ^–OOCCH₂OC₆H₄OCH₂COO^? spacers to form a 2–D network structure. The adjacent 2-D layers are further interlinked by hydrogen bonds to form a 3-D supermolecular structure.     

Lanthanide(III) Nitrate Complexes of Two 17 Membered N3O2-Donor Macrocycles

The interaction of lanthanide(III) ions with two N₃O₃-macrocycles, L¹ and L², derived from 2,6-bis(2-formylphenoxymethyl)pyridine and 1,2-diaminoethane has been investigated. Schiff-base macrocyclic lanthanide(III) complexes LnL¹(NO₃)₃ · xH₂O (Ln = Nd, Sm, Eu or Lu) have been prepared by direct reaction of L¹ and the appropriate hydrated lanthanide nitrate. The direct reaction between the diamine macrocycle L² and the hydrated lanthanide(III) nitrates yields complexes LnL²(NO₃)₃· H₂O only for Ln = Dy or Lu. The reduction of the Schiff-base macrocycle decreases the complexation capacity of the ligand towards the Ln(III) ions. The complexes have been characterised by elemental analysis, molar conductivity data, FAB mass spectrometry, IR and, in the case of the lutetium complexes, ¹H NMR spectroscopy.     

Poly[aqua(μ3‐benzene‐1,2‐dicarboxylato)bis(μ3‐hydroxido)bis(μ2‐isonicotinato)dierbium(III) monohydrate] and the thulium analogue

The two isomorphous lanthanide coordination polymers, {[Ln₂(C₆H₄NO₂)₂(C₈H₄O₄)(OH)₂(H₂O)]·H₂O}_n (Ln = Er and Tm), contain two crystallographically independent Ln ions which are both eight‐coordinated by O atoms, but with quite different coordination environments. In both crystal structures, adjacent Ln atoms are bridged by μ₃‐OH groups and carboxylate groups of isonicotinate and benzene‐1,2‐dicarboxylate ligands, forming infinite chains in which the Er...Er and Tm...Tm distances are in the ranges 3.622 (3)–3.894 (4) and 3.599 (7)–3.873 (1) Å, respectively. Adjacent chains are further connected through hydrogen bonds and π–π interactions into a three‐dimensional supramolecular framework.     

2D l‐Di‐toluoyl‐tartaric acid Lanthanide Coordination Polymers: Toward Single‐component White‐Light and NIR Luminescent Materials

A series of five l ‐di‐p‐toluoyl‐tartaric acid (l ‐DTTA) lanthanide coordination polymers, namely {[Ln₄K⁴ L₆(H₂O)_x]?yH₂O}_n, [Ln=Dy ( 1 ), x=24, y=12; Ln=Ho ( 2 ), x=23, y=12; Ln=Er ( 3 ), x=24, y=12; Ln=Yb ( 4 ), x=24, y=11; Ln=Lu ( 5 ), x=24, y=12] have been isolated by simple reactions of H₂L (H₂L= L ‐DTTA) with LnCl₃?6 H₂O at ambient temperature. X‐ray crystallographic analysis reveals that complexes 1 – 5 feature two‐dimensional (2D) network structures in which the Ln³⁺ ions are bridged by carboxylate groups of ligands in two unique coordinated modes. Luminescent spectra demonstrate that complex 1 realizes single‐component white‐light emission, while complexes 2 – 4 exhibit a characteristic near‐infrared (NIR) luminescence in the solid state at room temperature.     

配合物(ArO)2Yb(NPh2)2K(THF)4(Ar=C6H2-t-Bu3-2,4,6)的合成、分子结构和催化行为

Reaction of anhydrous YbC13 with 2 equiv, of sodium 2,4,6-tri-tert-butylphenoxide (ArONa, Ar=C6H2-t-Bu3-2,4,6) and 2 equiv, of potassium diphenyl amide in THF afforded the first bis(aryloxo) amido-lanthanide complex of (ArO)2Yb(NPh2)2K(THF)4 (1). In 1, the ytterbium and potassium were bridged via diphenyl amido ligands.The ytterbium metal center was coordinated to two oxygen atoms of aryloxide ligands and two nitrogen atoms of diphenyl amido ligands in a conventional distorted tetrahedral fashion, while the potassium interacted in η^2-fashion with two phenyl rings of the diphenyl amido ligands besides four THF molecules. 1 displayed moderate catalytic activities for the polymerization of methyl methacrylate and acrylonitrile.     

Two Series of Homodinuclear Lanthanide Complexes: Greatly Enhancing Energy Barriers through Tuning Terminal Solvent Ligands in Dy2 Single‐Molecule Magnets

The utilization of 2‐ethoxy‐6‐{[(2‐hydroxy‐3‐methoxybenzyl)imino]methyl}phenol (H₂L) as a chelating ligand, in combination with the employment of alcohols (EtOH and MeOH) as auxiliary ligands, in 4 f‐metal chemistry afforded two series of dinuclear lanthanide complexes of compositions [Ln₂L₂(NO₃)₂(EtOH)₂] (Ln=Sm ( 1 ), Eu ( 2 ), Gd ( 3 ), Tb ( 4 ), Dy ( 5 ), Ho ( 6 ), Er ( 7 )) and [Ln₂L₂(NO₃)₂(MeOH)₂] (Ln=Sm ( 8 ), Eu ( 9 ), Gd ( 10 ), Tb ( 11 ), Dy ( 12 ), Ho ( 13 ), Er ( 14 )). The structures of 1 – 14 were determined by single‐crystal X‐ray crystallography. Complexes 1 – 7 are isomorphous. The two lanthanide(III) ions in 1 – 7 are doubly bridged by two deprotonated aminophenoxide oxygen atoms of two μ₂:η⁰:η¹:η²:η¹:η¹:η⁰‐L²⁻ ligands. One nitrogen atom, two oxygen atoms of the NO₃⁻ anion, two methoxide oxygen atoms of two ligand sets, and one oxygen atom of the terminally coordinated EtOH molecule complete the distorted dodecahedron geometry of each lanthanide(III) ion. Compounds 8 – 14 are isomorphous and their structures are similar to those of 1 – 7 . The slight difference between 1 – 7 and 8 – 14 stems from purposefully replacing the EtOH ligands in 1 – 7 with MeOH in 8 – 14 . Direct‐current magnetic susceptibility studies in the 2–300 K range reveal weak antiferromagnetic interactions for 3 , 4 , 7 , 10 , 11 , and 14 , and ferromagnetic interactions at low temperature for 5 , 6 , 12 , and 13 . Complexes 5 and 12 exhibit single‐molecule magnet (SMM) behavior with energy barriers of 131.3 K for 5 and 198.8 K for 12 . The energy barrier is significantly enhanced by dexterously regulating the terminal ligands. To rationalize the observed difference in the magnetic behavior, complete‐active‐space self‐consistent field (CASSCF) calculations were performed on two Dy₂ complexes. Subtle variation in the angle between the magnetic axes and the vector connecting two dysprosium(III) ions results in a weaker influence on the tunneling gap of individual dysprosium(III) ions by the dipolar field in 12 . This work proposes an efficient strategy for synthesizing Dy₂ SMMs with high energy barriers.     

Self-Assembly of Isopolyanion Clusters and Lanthanide-Organic Units into 2D Layers: (NH4)2{[Ln2(C7H4NO4)2(H2O)9][(H2W12O40)]}·nH2O (Ln?=?Gd, Tb, Ho)

Three novel 1:2 composite compounds prepared with the isopolyanions and lanthanide-organic units, (NH₄)₂{[Ln₂(HL)₂(H₂O)₉][(H₂W₁₂O₄₀)]}·nH₂O (Ln = Gd³⁺ (1), Tb³⁺ (2), n = 15; Ho³⁺ (3), n = 10; L = pyridine-3,5-dicarboxylate) were synthesized at room temperature and characterized by routine methods. X-ray structural analysis reveals that these structures are isomorphic: two crystallographically independent Ln³⁺ ions (Ln1 and Ln2) locate in different coordination environments; two ligands plays dissimilar coordination mode; the isopolyanion cluster acts as a tridentate ligand and connects three Ln³⁺ ions (Ln1, Ln1′ and Ln2) forming an unusual 2D undee-layer. The room temperature luminescent of 2 has been studied and exhibits a Tb³⁺ characteristic emission in the range of 450–650 nm.     

Synthesis and Structures of Homoleptic Monomeric Potassium Aryloxolanthanoidate(III) Complexes

Reaction of lanthanoid tris(2, 6‐diphenylphenolates) [Ln(Odpp)₃] with KOdpp in 1, 2, 4, 5‐tetramethylbenzene (durene) at 200‐250 °C affords [K{Ln(OC₆H₃Ph₂‐2, 6)₄}], (Ln = La ( 1 ) or Nd ( 2 )) and 2 has also been obtained from the reaction of [Nd(Odpp)₃] with potassium hydride. In the solid state, 1 and 2 are monomeric bimetallics in which Ln is surrounded by a distorted tetrahedral array of oxygen atoms. Two Odpp ligands are oxygen bridged between K and Ln and also are η⁴‐Ph linked to potassium. One Odpp ligand bridges the metals in an O(Ln): η⁶‐Ph(K) manner that is new for lanthanoid complexes of this ligand, with no close K‐O contact, and the remaining Odpp is terminal on the Ln.     

两个双核稀土-自由基化合物的合成、结构及磁性

以乙酰丙酮为共配体的稀土配合物与2-羟基苯取代的自由基配体进行反应得到2个新颖的稀土-自由基配合物[Ln₂（acac）₄（NIT-PhO）₂]（Ln=Tb（1）,Y（2）;acac=乙酰丙酮,NIT-PhOH=2-（2''-hydroxyphenyl）-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide）。2个配合物的结构相同,均是通过2个自由基配体上的羟基氧原子桥联2个稀土离子构成双核结构。直流磁化率的研究表明配合物2具有弱的反铁磁性质。     

Heterodinuclear Lanthanoid‐Containing Polyoxometalates: Stepwise Synthesis and Single‐Molecule Magnet Behavior

Polyoxometalates (POMs) with heterodinuclear lanthanoid cores, TBA₈H₄[{Ln(μ₂‐OH)₂Ln′}(γ‐SiW₁₀O₃₆)₂] ( LnLn′ ; Ln=Gd, Dy; Ln′=Eu, Yb, Lu; TBA=tetra‐n‐butylammonium), were successfully synthesized through the stepwise incorporation of two types of lanthanoid cations into the vacant sites of lacunary [γ‐SiW₁₀O₃₆]^8? units without the use of templating cations. The incorporation of a Ln³⁺ ion into the vacant site between two [γ‐SiW₁₀O₃₆]^8? units afforded mononuclear Ln³⁺‐containing sandwich‐type POMs with vacant sites ( Ln1 ; TBA₈H₅[{Ln(H₂O)₄}(γ‐SiW₁₀O₃₆)₂]; Ln=Dy, Gd, La). The vacant sites in Ln1 were surrounded by coordinating W? O and Ln? O oxygen atoms. On the addition of one equivalent of [Ln′(acac)₃] to solutions of Dy1 or Gd1 in 1,2‐dichloroethane (DCE), heterodinuclear lanthanoid cores with bis(μ₂‐OH) bridging ligands, [Dy(μ₂‐OH)₂Ln′]⁴⁺, were selectively synthesized ( LnLn′ ; Ln=Dy, Gd; Ln′=Eu, Yb, Lu). On the other hand, La1 , which contained the largest lanthanoid cation, could not accommodate a second Ln′³⁺ ion. DyLn′ showed single‐molecule magnet behavior and their energy barriers for magnetization reversal (ΔE/k_B) could be manipulated by adjusting the coordination geometry and anisotropy of the Dy³⁺ ion by tuning the adjacent Ln′³⁺ ion in the heterodinuclear [Dy(μ₂‐OH)₂Ln′]⁴⁺ cores. The energy barriers increased in the order: DyLu (ΔE/k_B=48 K)< DyYb (53 K)< DyDy (66 K)< DyEu (73 K), with an increase in the ionic radii of Ln′³⁺; DyEu showed the highest energy barrier.     

Hydrothermal synthesis and crystal structure of two new lanthanide coordination polymers with 1,2-phenylenediacetate

Two new compounds {[Ln₂(1,2-pda)₃(H₂O)₂]·?2H₂O} _n (1,2-H₂pda?=?1,2-phenylenediacetic acid, Ln?=?Tb, 1; Ho, 2) were prepared by hydrothermal reaction and characterized by X-ray crystallography. The Ln³⁺ is nine-coordinate by eight oxygen atoms of six 1,2-pda ligands and one oxygen of water. Ln³⁺ ions are bridged by 1,2-pda ligands via bridging/chelating-bridging pentadentate and chelating-bridging/chelating-bridging hexadentate coordination to form 3-D framework structures. Complex 1 emits strong green fluorescence corresponding to ⁵D₄???⁷F_j (j?=?6–3) transitions of the Tb³⁺.     

Syntheses, crystal structures and vibrational spectra of KLn(SO4)2·H2O (Ln=La, Nd, Sm, Eu, Gd, Dy)

The potassium lanthanide double sulphates KLn(SO₄)₂·H₂O (Ln=La, Nd, Sm, Eu, Gd, Dy) were obtained by evaporation of aqueous reaction mixtures of rare earth (III) sulphates and potassium thiocyanate at 298 K. X-ray single-crystal investigations show that KLn(SO₄)₂·H₂O (Ln=Nd, Sm, Eu, Gd, Dy) crystallise monoclinically (Ln=Sm: P2₁/c, Z=4, a=10.047(1), b=8.4555(1), c=10.349(1) Å, wR2=0.060, R1=0.024, 945 reflections, 125 parameters) while KLa(SO₄)₂·H₂O adopts space group P3₂21 (Z=3, a=7.1490(5), c=13.2439(12) Å, wR2=0.038, R1=0.017, 695 reflections, 65 parameters). The coordination environment of the lanthanide ions in KLn(SO₄)₂·H₂O is different in the case of the Nd/Sm/Gd and the Eu/Dy compounds, respectively. In the first case the Ln atoms are nine-fold coordinated in contrast to the latter where the Ln ions are eight-fold coordinated by oxygen atoms. The vibrational spectra of KLn(SO₄)₂·H₂O and the UV-vis reflection spectra of KEu(SO₄)₂·H₂O and KNd(SO₄)₂·H₂O are also reported.     

Anionic lanthanide complexes with 3-methyl-4-formyl-1-phenyl-5-pyrazolone

The coordination compounds Na[LnL₄] · 2H₂O and [NBu₄][LnL₄] (Ln = Nd, Sm, Eu, Tb; HL is 3-methyl-4-formyl-1-phenyl-5-pyrazolone) have been synthesized and studied by IR spectroscopy and thermogravimetry. According to X-ray diffraction data, the coordination polyhedra of lanthanides are shaped as square antiprisms and formed by the oxygen atoms of four deprotonated moieties of the enol form of 4-formyl-5-pyrazolone. In the complex Na[EuL₄] · 2H₂O, sodium cations are bonded to the two nitrogen atoms of pyrazole heterocycles, combining discrete complex anions into two interpenetrating three-dimensional frameworks. Polycrystalline samples of neodymium(III), samarium(III), and terbium(III) complexes manifest intense luminescence in the spectral regions that are typical for them.     

The Syntheses,Structures, and Magnetic Properties of Four 2D Lanthanide(III)‐naphthalenedicarboxylic Complexes

Four Ln‐NDC coordination polymers [Ln(NDC)(HNDC)(H₂O)] (Ln = La ( 1 ), Pr ( 2 ), Nd ( 3 ), Sm ( 4 ), H₂NDC = 1,4‐naphthalenedicarboxylic acid) were hydrothermally synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single‐crystal X‐ray diffraction. Compounds 1 – 4 are isomorphous, and their structures display a layer constructed from a Ln‐organic chain and NDC^2– ligand, in which the H₂NDC ligands adopt two different acidity‐dependent types and coordination modes: HNDC^1– with μ‐η¹:η¹ and NDC^2– with μ‐η¹:η²:η¹:η². The 3D supramolecular networks of 1 – 4 are mainly controlled by hydrogen bonds interactions. The magnetic susceptibilities of complexes 2 – 4 reveal overall antiferromagnetic interactions between the Ln^III ions. In addition, thermogravimetric analysis of compound 2 is described.     

Five Rare μ4‐O‐Centered Ln6 Clusters with Single‐Molecule Magnet Behavior for Dy6

Five hexanuclear lanthanide clusters of composition [Ln₆(μ₄‐O)₂(HCOO)₂L₄(HL′)₂(dmf)₂] [Ln=Dy ( 1 ), Er ( 2 ), Ho ( 3 ), Tb ( 4 ), Gd ( 5 ); H₂L=2‐{[2‐(hydroxymethyl)phenylimino]methyl}‐6‐methoxyphenol; H₃L′=3‐{[2‐(hydroxymethyl)phenylimino]methyl}benzene‐1,2‐diol; H₃L′ was derived in situ from the H₂L ligand] were prepared under solvothermal conditions. The [Ln₆] cores of 1 – 5 possess an unprecedented motif, namely, two tetrahedron Ln₄ units sharing an edge and two vertices. The six Ln^III ions of 1 – 5 are connected through two μ₄‐O anions. Magnetic susceptibility studies reveal that complex 1 exhibits frequency dependence of the alternating current susceptibility typical of single‐molecule magnets. Complex 1 possesses a relatively large energy barrier of 85 K among all of the reported Dy₆ single‐molecule magnets.     

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.     

Nitratkomplexe der Seltenerdelemente mit 2,2′-Bipyridin-N,N′-dioxid

Compounds ScL ₂(NO₃)₃·2 H₂O,LnL ₂(NO₃)₃·H₂O (Ln=Pr, Sm, Eu, Gd, Tb),LnL ₂(NO₃)₃·3 H₂O (Ln=Nd, Dy, Ho, Er),LnL ₃(NO₃)₃ (Ln=Pr, Nd) andLnL ₃(NO₃)₃· ·3 H₂O (Ln=Sc, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were isolated. They were investigated by means of thermoanalysis, IR spectroscopy, X-ray diffraction and molar conductivity.

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L=2,2-Bipyridin-N,N-dioxid=bpyO₂=C₁₀H₈N₂O₂.     

Syntheses,characterization and thermal properties of the lanthanide complexes with 2-mercaptonicotinic acid and 1,10-phenanthroline

Fourteen new complexes with the general formula of Ln(Hmna)₃(phen) (H₂mna = 2-mercaptonicotinic acid and phen = 1,10-phenanthroline) were synthesized and characterized by elemental analyses, IR spectra and thermogravimetric analyses. In addition, molar specific heat capacities were determined by a microcalorimeter at 298.15 K. The IR spectra of the complexes showed that the Ln³⁺ coordinated with the oxygen atoms of H₂mna and the nitrogen atoms of phen. The complexes decomposed directly to oxides Ln₂O₃, CeO₂, Pr₆O₁₁, and Tb₄O₇ in one step. The values of molar specific heat capacities for fourteen solid complexes were plotted against the atomic numbers of lanthanide, which presented as “tripartite effect”. It suggested a certain amount of covalent character existed in the bond of Ln³⁺ and ligands, according with nephelauxetic effect of 4f electrons of rare earth ions. The article is published in the original.     

Synthesis of Lanthanide Coordination Polymers with Benzophenone-4,4′-dicarboxylate： Effect of Lanthanide Contraction on Structures

Four lanthanide coordination polymers with benzophenone‐4,4′‐dicarboxylic acid (H₂bpndc) and 1,10‐phenanthroline (phen), [Ln₂(bpndc)₃(phen)] (Ln=La (1), Pr (2) and Tb (3)), [Yb(bpndc)₁₅(phen)].05H₂O (4) were obtained through solvothermal synthesis. The crystallographic data show that 1, 2, and 3 are isostructural, the Ln(III) ions in 1, 2 and 3 are all eight‐ and ten‐coordinated, respectively, and thus the Ln(III) ions are connected by bpndc ligands, resulting in an interpenetrating 3D structure. While in 4, the Yb(III) ions are eight‐coordinated and connected by bpndc ligands into a 3D structure with 1D rhombic channels, which result from the effect of lanthanide contraction from La(III) to Yb(III) ions, and the bpndc ligands in 1, 2, 3, and 4 display three types of coordination modes.