Syntheses, structures, and luminescent and magnetic properties of novel three-dimensional lanthanide complexes with 1,3,5-benzenetriacetate

Five novel lanthanide complexes with the formulas [Nd(bta)(H2O)2.4.35H2O]n(1), [Sm(bta)(H2O)2.4.5H2O]n (2), [Eu(bta)(H2O).1.48H2O]n (3), [Tb(bta)(H2O).1.31H2O]n (4), and [Yb(bta)(H2O).H2O]n (5) (H3bta = 1,3,5-benzenetriacetic acid) have been prepared by using the corresponding lanthanide salt and H3bta. The results of an X-ray crystallographic analysis revealed that all the complexes have three-dimensional channel-like structures, in which the bta3- ligands adopt different coordination modes: monodentate and mu2-eta2:eta1-bridging coordination modes in 1, 2, and 5 and mu2-eta1:eta1-bridging and mu2-eta2:eta1-bridging coordination modes in 3 and 4, respectively. Complexes 1 and 2, as well as 3 and 4, are isostructural, respectively, in which all the Ln(III) (Ln = Nd, Sm, Eu, and Tb) atoms are nine-coordinated, while the Yb(III) atoms in complex 5 are eight-coordinated. Both complexes 3 and 4 showed strong luminescence upon excitation, and their luminescence decay curves fit well with single exponential decays of which the lifetime is 0.45 ms for 3 and 1.0 ms for 4. The magnetic properties of the complexes were investigated in the temperature range of 1.8-300 K.     

Lanthanide complexes of chiral 3 + 3 macrocycles derived from (1R,2R)-1,2-diaminocyclohexane and 2,6-diformyl-4-methylphenol

The enantiopure amine macrocycle H(3)L, as well as the parent macrocyclic Schiff base H(3)L1, the 3 + 3 condensation product of (1R,2R)-1,2-diaminocyclohexane and 2,6-diformyl-4-methylphenol, are able to form mononuclear complexes with lanthanide(III) ions. The lanthanide(III) complexes of H(3)L have been studied in solution using NMR spectroscopy and electrospray mass spectrometry. The NMR spectra indicate the presence of complexes of low C(1) and C(2) symmetry. The (1)H and (13)C NMR signals of the Lu(III) complex obtained from H(3)L have been assigned on the basis of COSY, TOCSY, NOESY, ROESY and HMQC spectra. The NMR data reveal unsymmetrical binding of lanthanide(III) ion and the presence of a dynamic process corresponding to rotation of Lu(III) within the macrocycle. The [Ln(H(4)L)(NO(3))(2)](NO(3))(2)(Ln = Sm(III), Eu(III), Dy(III), Yb(III) and Lu(III)) complexes of the cationic ligand H(4)L(+) have been isolated in pure form. The X-ray analysis of the [Eu(H(4)L)(NO(3))(2)](NO(3))(2) complex confirms the coordination mode of the macrocycle determined on the basis of NMR results. In this complex the europium(III) ion is bound to three phenolate oxygen atoms and two amine nitrogen atoms of the monoprotonated macrocycle H(4)L(+), as well as to two axial bidendate nitrate anions. In the presence of a base, mononuclear La(III), Ce(III) and Pr(III) complexes of the deprotonated form of the ligand L(3-) can be obtained. When 2 equivalents of Pr(III) are used in this synthesis Na(3)[Pr(2)L(NO(3))(2)(OH)(2)](2)NO(3).5H(2)O is obtained. The NMR, ES MS and an X-ray crystal model of this complex show coordination of two Pr(III) ions by the macrocycle L. The X-ray crystal structure of the free macrocycle H(3)L1 has also been determined. In contrast to macrocyclic amine H(3)L, the Schiff base H(3)L1 adopts a cone-type conformation resembling calixarenes.     

Trinuclear lanthanide complexes of a compartmental ligand N,N'-bis(2-pyridinyl)-2,6-pyridinedicarboxamide: a spectroscopic investigation

Trinuclear lanthanide complexes of the formula [Ln(3)(PPDA)(NO(3))(6)(H(2)O)(2)].NO(3).2H(2)O where Ln=La(III), Pr(III), Sm(III), Nd(III), Eu(III) Gd(III) Tb(III), Dy(III) and Y(III); H(2)PPDA=N,N'-bis(2-pyridinyl)-2,6-pyridinedicarboxamide, have been isolated. The complexes were characterized by elemental analyses, conductivity measurements, magnetic susceptibility measurements and spectral (IR, NMR, UV-vis, fluorescence, FAB and EPR) and thermal studies.     

Preparation, Characterization and Properties of Two New Lanthanide(III)-5-(2-pyridyl)tetrazolate Complexes

Two new mononuclear lanthanide(III) complexes Ln(pytz)3(H2O)3·(H2O)3.5[Ln=Tb(1); Eu(2); Hpytz= 5-(2-pyridyl)tetrazole] were synthesized by reacting Hpytz with the corresponding lanthanide(III) ions and characterized. The single crystal X-ray diffraction analysis reveals that complexes 1 and 2 are isostructural and the lanthanide(III) ions in both complexes 1 and 2 are nine-coordinated, with three oxygen atoms of three coordination water molecules and six nitrogen atoms of three pytz ligands, forming a monocapped square antiprism. Extensive hydrogen bonds exist, resulting in a three-dimensional supramolecular network structure by hydrogen-bonds in both complexes 1 and 2, respectively. Complex 1 exhibits typical green fluorescence of Tb(III) ion and complex 2 red fluorescence of Eu(III) ion, in solid state at room temperature.     

Isolations and characterization of highly water-soluble dimeric lanthanide citrate and malate with ethylenediaminetetraacetate

Highly water-soluble lanthanum and cerium citrates or malates with ethylenediaminetetraacetate (NH(4))(8)[Ln(2)(Hcit)(2)(EDTA)(2)]·9H(2)O [Ln = La, 1; Ce, 2], K(8)[La(2)(Hcit)(2)(EDTA)(2)]·16H(2)O (3) and K(6)[Ln(2)(Hmal)(2)(EDTA)(2)]·14H(2)O [Ln = La, 4; Ce, 5] (H(4)cit = citric acid, H(3)mal = malic acid, and H(4)EDTA = ethylenediaminetetracetic acid) were prepared from the reactions of lanthanide ethylenediaminetetraacetate trihydrates with citric or malic acid at pH 5.0-6.5. These compounds were characterized by elemental analyses, IR, TG-DTG, solution (13)C{(1)H} NMR, solid state (13)C NMR spectra and X-ray structural analyses. The main structural feature of the compounds consists of a dinuclear unit deca-coordinated by EDTA and citrate or malate. The α-hydroxy and α-carboxy groups of citrate and malate chelate in five-membered ring with one lanthanide ion, while one of the β-carboxy group coordinates with the other lanthanide ion, forming a dimeric structure. The other pendent β-carboxy groups in 1-3 form very strong intramolecular hydrogen bond with α-hydroxy groups [O1O7 2.594(4), 2.587(8) and 2.57(1) ? for 1-3 respectively]. (13)C NMR spectra of the lanthanum compounds show obvious downfield shifts based on solid and solution NMR measurements, indicating the coordinations of mixed-ligand in lanthanum complexes, while highfield shifts are observed in cerium complexes.     

Controlled hydrolysis of lanthanide complexes of the N-donor tripod tris(2-pyridylmethyl)amine versus bisligand complex formation

The reaction of the lanthanide salts LnI3(thf)4 and Ln(OTf)3 with tris(2-pyridylmethyl)amine (tpa) was studied in rigorously anhydrous conditions and in the presence of water. Under rigorously anhydrous conditions the successive formation of mono- and bis(tpa) complexes was observed on addition of 1 and 2 equiv of ligand, respectively. Addition of a third ligand equivalent did not yield additional complexes. The mono(tpa) complex [Ce(tpa)I3] (1) and the bis(tpa) complexes [Ln(tpa)2]X3 (X = I, Ln = La(III) (2), Ln = Ce(III) (3), Ln = Nd(III) (4), Ln = Lu(III) (5); X = OTf, Ln = Eu(III) (6)) were isolated under rigorously anhydrous conditions and their solid-state and solution structures determined. In the presence of water, 1H NMR spectroscopy and ES-MS show that the successive addition of 1-3 equiv of tpa to triflate or iodide salts of the lanthanides results in the formation of mono(tpa) aqua complexes followed by formation of protonated tpa and hydroxo complexes. The solid-state structures of the complexes [Eu(tpa)(H2O)2(OTf)3] (7), [Eu(tpa)(mu-OH)(OTf)2]2 (8), and [Ce(tpa)(mu-OH)(MeCN)(H2O)]2I4 (9) have been determined. The reaction of the bis(tpa) lanthanide complexes with stoichiometric amounts of water yields a facile synthetic route to a family of discrete dimeric hydroxide-bridged lanthanide complexes prepared in a controlled manner. The suggested mechanism for this reaction involves the displacement of one tpa ligand by two water molecules to form the mono(tpa) complex, which subsequently reacts with the noncoordinated tpa to form the dimeric hydroxo species.     

Synthesis and characterization of benzoxazine-functionalized amine bridged bis(phenolate) lanthanide complexes and their application in the ring-opening polymerization of cyclic esters

The synthesis and structures of lanthanide complexes supported by benzoxazine-functionalized amine bridged bis(phenolate) ligand 6,6'-(2-(8-tert-butyl-6-methyl-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethylazanediyl)bis(methylene)bis(2-tert-butyl-4-methylphenolato) (L(2-)) are described. Salt metathesis reaction between lanthanide trichloride and 2 eq of LNa(2) in THF at room temperature afforded the corresponding "ate" complexes [L(2)LnNa(THF)(2)] (Ln[double bond, length as m-dash]Y (1), Nd (2), Er (3), Yb (4)). Further treatment of the product with 18-crown-6 afforded discrete ion-pair complexes [L(2)Ln][(18-crown-6)Na(THF)(2)] (Ln[double bond, length as m-dash]Y (5), Yb (6)). The single-crystal structural analyses of 1 and 3-6 revealed that the lanthanide cation and the sodium cation were bridged by two phenolate oxygen atoms in complexes 1, 3 and 4, while in complexes 5 and 6, the anion comprises a lanthanide cation coordinated by two L(2-) and the cation is comprised of a sodium cation surrounded by an 18-crown-6 and two THF molecules. These complexes were found to exhibit distinct activities towards the ring-opening polymerization of ε-caprolactone and l-lactide.     

Syntheses and crystal structures of dinuclear complexes containing d-block and f-block luminophores. Sensitization of NIR luminescence from Yb(III), Nd(III), and Er(III) centers by energy transfer from Re(I)- and Pt(II)-bipyrimidine metal centers

Mononuclear complexes [Re(bpym)(CO)(3)Cl] and [Pt(bpym)(CC-C(6)H(4)CF(3))(2)] (bpym = 2,2'-bipyrimidine), in which one of the bipyrimidine sites is vacant, have been used as "complex ligands" to prepare heterodinuclear d-f complexes in which a lanthanide tris(1,3-diketonate) unit is attached to the secondary bipyrimidine site to evaluate the ability of d-block chromophores to act as antennae for causing sensitized near-infrared (NIR) luminescence from adjacent lanthanide(III) centers. The two sets of complexes so prepared are [Re(CO)(3)Cl(mu-bpym)Ln(fod)(3)] (abbreviated as Re-Ln; where Ln = Yb, Nd, Er) and [(F(3)C-C(6)H(4)-CC)(2)Pt(mu-bpym)Ln(hfac)(3)] (abbreviated as Pt-Ln; where Ln = Nd, Gd). Members of both series have been structurally characterized; the metal-metal separation across the bipyrimidine bridge is approximately 6.3 A in each case. In these complexes, the (3)MLCT (MLCT = metal to ligand charge-transfer) luminescences of the mononuclear [Re(bpym)(CO)(3)Cl] and [Pt(bpym)(CC-C(6)H(4)CF(3))(2)] complexes are quenched by energy transfer to those lanthanides (Ln = Yb, Nd, Er) that have low-lying f-f states capable of NIR luminescence; as a result, sensitized NIR luminescence is seen from the lanthanide center following excitation of the d-block unit. In the solid state, quenching of the luminescence from the d-block chromophore is complete, indicating efficient d --> f energy transfer, as a result of the short metal-metal separation across the bipyrimidine bridge. In a CH(2)Cl(2) solution, partial dissociation of the dinuclear complexes into the mononuclear units occurs, with the result that some (3)MLCT luminescence is observed from mononuclear [Re(bpym)(CO)(3)Cl] or [Pt(bpym)(CC-C(6)H(4)CF(3))(2)] present in the equilibrium mixture. Solution UV-vis and luminescence titrations, carried out by the addition of portions of Ln(fod)(3)(H(2)O)(2) or Ln(hfac)(3)(H(2)O)(2) to the d-block complex ligands, indicate that binding of the lanthanide tris(1,3-diketonate) unit at the secondary bipyrimidine site to give the d-f dinuclear complexes occurs with an association constant of ca. 10(5) M(-)(1).     

Gadolinium(III) complexes of mono- and diethyl esters of monophosphonic acid analogue of DOTA as potential MRI contrast agents: solution structures and relaxometric studies

Two new macrocyclic DOTA-like chelates containing one phosphonate pendant arm were synthesised as potential contrast agents for MRI (magnetic resonance imaging). The chelates bind to the lanthanide(III) in an octadentate manner, via four nitrogen atoms, three carboxylate and one phosphonate oxygen atoms. Solution structures of [Ln(do3ap(OEt2))(H(2)O)] and [Ln(do3ap(OEt))(H(2)O)](-) were studied using (31)P and (1)H NMR spectroscopy and SAP (square-antiprismatic)/TSAP (twisted square-antiprismatic) isomerism was observed. Depending on the nature of the lanthanide(III) ion, the lanthanide(III) complexes of H(4)do3ap(OEt) are present in solution as up to four different diastereoisomers observable with NMR. The TSAP isomer is the most abundant at the beginning of the lanthanide series and, with a decrease of the ionic radius of lanthanide(III) ions, both TSAP and SAP forms were observed. A second interconversion (SAP<-->TSAP') becomes important at the end of the series (TSAP' means the TSAP species without a coordinated water molecule). The remaining axial coordination site is occupied by one water molecule for the Gd(3+)-complex. The calculated fraction of the TSAP isomer in the gadolinium(III) complexes increases in the order [Gd(DOTA)(H(2)O)](-) < [Gd(do3ap(OEt2))(H(2)O)] < [Gd(do3ap(OEt))(H(2)O)](-) < [Gd(do3ap)(H(2)O)](2-). Gadolinium(III) complexes of phosphorus-containing chelates, generally, have the advantage of a relatively fast water exchange rate due to a greater sterical demand of the phosphorus acid moiety and of the presence of the second-sphere water shell, which also contributes to the overall relaxivity. The [Gd(do3ap(OEt2))(H(2)O)] and [Gd(do3ap(OEt))(H(2)O)](-) complexes were studied by variable-temperature (17)O NMR and (1)H NMRD. The experimental data were evaluated simultaneously with commonly used equations based on Solomon-Bloembergen-Morgan approximation, extended by a contribution of the second coordination sphere. The water exchange rates were found to be strongly dependent on the TSAP/SAP isomeric ratio and the overall charge of the complex: the monoanionic [Gd(do3ap(OEt))(H(2)O)](-) complex with TSAP molar fraction equal to 0.36 has the water exchange rate of 20 x 10(6) s(-1) (tau(M) = 50 ns) while neutral [Gd(do3ap(OEt2))(H(2)O)] complex with TSAP molar fraction 0.28 has an exchange rate equal to 4.4 x 10(6) s(-1) (tau(M) = 227 ns).     

Lanthanide complexes of the chiral hexaaza macrocycle and its meso-type isomer: solvent-controlled helicity inversion

Lanthanide(III) complexes of the enantiopure chiral hexaaza tetraamine macrocycle L, 2(R),7(R),18(R),23(R)-1,8,15,17,24,31-hexaazatricyclo[25.3.1.1.0.0]-dotriaconta-10,12,14,26,28,30-hexaene, as well as of its meso-type 2(R),7(R),18(S),23(S)-isomeric macrocycle L1, have been synthesized and characterized by spectroscopic methods. The 2D NMR spectra confirm the identity of these complexes and indicate C2 symmetry of the [LnL]3+ and Cs symmetry of the [LnL1]3+ complexes. The crystal structures of the [PrL(NO3)(H2O)2](NO3)2, [EuL(NO3)(H2O)2](NO3)2, [DyL(NO3)2]2[Dy(NO3)5] x 5CH3CN, [YbL(NO3)2]2[Yb(NO3)5] x 5CH3CN, [YbL(H2O)2](NO3)3 x H2O, and [EuL1(NO3)(H2O)2]0.52[EuL1(NO3)2]0.48(NO3)1.52 x 0.48H2O complexes have been determined by single-crystal X-ray diffraction. In all complexes, the lanthanide(III) ions are coordinated by six nitrogen atoms of the macrocycle L or L1, but for each type of complex, the conformation of the macrocycle and the axial ligation are different. The crystallographic, NMR, and CD data show that the [YbL]3+ complex exists in two stable forms. Both forms of the Yb(III) complex have been isolated, and their interconversion was studied in various solvents. The two forms of [YbL]3+ complex correspond to two diastereomers of ligand L, which differ in the sense of the helical twist and the configuration at the stereogenic amine nitrogen atoms. In one of the stereoisomers, the macrocycle L of (RRRR) configuration at the stereogenic cyclohexane carbon atoms adopts the (RSRS) configuration at the amine nitrogen atoms, while in the other stereoisomer, the macrocycle L of (RRRR) configuration at the stereogenic cyclohexane carbon atoms adopts the (SSSS) configuration at the amine nitrogen atoms. The (RRRR)(RSRS) isomer is quantitatively converting to the (RRRR)(SSSS) isomer in water solution, while the reverse process is observed for an acetonitrile solution, thus representing the rare case of helicity inversion controlled by the solvent.     

A convenient route to lanthanide triiodide THF solvates. Crystal structures of LnI(3)(THF)(4) [Ln = Pr] and LnI(3)(THF)(3.5) [Ln = Nd, Gd, Y

The reaction between 1.5 equiv of elemental iodine and rare earth metals in powder form in THF at room temperature gives the rare earth triiodides LnI(3)(THF)(n)() in good yields. Purification by Soxhlet extraction of the crude solids with THF reliably gives the THF adducts LnI(3)(THF)(4) [Ln = La, Pr] and LnI(3)(THF)(3.5) [Ln = Nd, Sm, Gd, Dy, Er, Tm, Y] as microcrystalline solids. X-ray crystallography reveals that the early, larger lanthanide iodide PrI(3)(THF)(4) crystallizes as discrete molecules having a pentagonal bipyramidal structure, whereas the later, smaller lanthanide iodides LnI(3)(THF)(3.5) [Ln = Nd, Gd, Y] crystallize as solvent-separated ion pairs [LnI(2)(THF)(5)][LnI(4)(THF)(2)] in which the cations adopt a pentagonal bipyramidal geometry and the anions adopt an octahedral geometry in the solid state.     

Trinuclear heterobimetallic Ni2Ln complexes [L2Ni2Ln][ClO4] (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er; LH3=(S)P[N(Me)NCH-C6H3-2-OH-3-OMe]3): from simple paramagnetic complexes to single-molecule magnet behavior

The reaction of LH3 with Ni(ClO4)(2).6H 2O and lanthanide salts in a 2:2:1 ratio in the presence of triethylamine leads to the formation of the trinuclear complexes [L2Ni2Ln][ClO4] (Ln=La (2), Ce (3), Pr (4), Nd (5), Sm (6), Eu (7), Gd (8), Tb (9), Dy (10), Ho (11) and Er (12) and L: (S)P[N(Me)NCH-C6H3-2-O-3-OMe]3). The cationic portion of these complexes consists of three metal ions that are arranged in a linear manner. The two terminal nickel(II) ions are coordinated by imino and phenolate oxygen atoms (3N, 3O), whereas the central lanthanide ion is bound to the phenolate and methoxy oxygen atoms (12O). The Ni-Ni separations in these complexes range from 6.84 to 6.48 A. The Ni-Ni, Ni-Ln and Ln-O phenolate bond distances in 2-12 show a gradual reduction proceeding from 2 to 12 in accordance with lanthanide contraction. Whereas all of the compounds (2-12) are paramagnetic systems, 8 displays a remarkable ST=(11)/2 ground state induced by an intramolecular Ni. . .Gd ferromagnetic interaction, and 10 is a new mixed metal 3d/4f single-molecule magnet generated by the high-spin ground state of the complex and the magnetic anisotropy brought by the dysprosium(III) metal ion.     

Coaggregation of paramagnetic d- and f-block metal ions with a podand-framework amine phenol ligand

This report covers initial studies in the coaggregation of nickel (Ni2+) and lanthanide (Ln3+) metal ions to form complexes with interesting structural and magnetic properties. The tripodal amine phenol ligand H3tam (1,1,1-tris(((2-hydroxybenzyl)amino)methyl)ethane) is shown to be particularly accommodating with respect to the geometric constraints of both transition and lanthanide metal ions, forming isolable complexes with both of these ion types. In the solid-state structure of [Ni(H2tam)(CH3CN)]PF6.2.5CH3CN.0.5CH3OH (1), the Ni(II) center has a distorted octahedral geometry, with an N3O2 donor set from the [H2tam]- ligand and a coordinated solvent (acetonitrile) occupying the sixth site. The reaction of stoichiometric amounts of H3tam with the Ni(II) ion in the presence of lanthanide(III) ions provides [LnNi2(tam)2]+ cationic complexes which contain coaggregated metal ions. These complexes are isolable and have been characterized by a variety of analytical techniques, with mass spectrometry proving to be particularly diagnostic. The solid-state structures of [LaNi2(tam)2(CH3OH)1/2(CH3CH2OH)1/2(H2O)]ClO4.0.5CH3OH.0.5CH3CH2OH.4H2O (2), [DyNi2(tam)2(CH3OH)(H2O)]ClO4.CH3OH. H2O(6), and [YbNi2(tam)2(H2O)]ClO4.2.58H2O(9) have been determined. Each complex contains two octahedral Ni(II) ions, each of which is encapsulated by the ligand tam3- in an N3O3 coordination sphere; each [Ni(tam)]-unit caps the lanthanide(III) ion via bridging phenoxy oxygen donor atoms. In 2, La3+ is eight-coordinated, while in 6, Dy(III) is seven- (to "weakly eight-") coordinated, and Yb(III) in 9 has a six-coordination environment. The complexes are symmetrically different, 2 possessing C2 symmetry and 6 and 9 having C1 symmetry. Magnetic studies of 2, 6, and 9 indicate that antiferromagnetic exchange coupling between the Ni(II) and Ln(III) ions increases with decreasing ionic radius of Ln(III).     

Syntheses, characterization, biological activity and fluorescence properties of bis-(salicylaldehyde)-1,3-propylenediimine Schiff base ligand and its lanthanide complexes

Eight new lanthanide metal complexes [LnL(NO(3))(2)]NO(3) {Ln(III) = Nd, Dy, Sm, Pr, Gd, Tb, La and Er, L = bis-(salicyladehyde)-1,3-propylenediimine Schiff base ligand} were prepared. These complexes were characterized by elemental analysis, thermogravimetric analysis (TGA), molar conductivity measurements and spectral studies ((1)H NMR, FT-IR, UV-vis, and luminescence). The Schiff base ligand coordinates to Ln(III) ion in a tetra-dentate manner through the phenolic oxygen and azomethine nitrogen atoms. The coordination number of eight is achieved by involving two bi-dentate nitrate groups in the coordination sphere. Sm, Tb and Dy complexes exhibit the characteristic luminescence emissions of the central metal ions attributed to efficient energy transfer from the ligand to the metal center. Most of the complexes exhibit antibacterial activity against a number of pathogenic bacteria.     

Influence of Schiff base and lanthanide metals on the synthesis, stability, and reactivity of monoamido lanthanide complexes bearing two Schiff bases

The monoamido lanthanide complexes stabilized by Schiff base ligand L(2)LnN(TMS)(2) (L = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-8-C(9)H(6)N, Ln = Yb (1), Y (2), Eu (3), Nd (4), and La (5)) were synthesized in good yields by the reactions of Ln[N(TMS)(2)](3) with 1.8 equiv of HL in hexane at room temperature. It was found that the stability of 1-5 depends greatly on the size of the lanthanide metals with the increasing trend of Yb ≈ Y < Nd < La. The amine elimination of Ln[N(TMS)(2)](3) with the bulky bidentate Schiff base HL' (L' = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-2,6-Pr(i)(2)-C(6)H(3)) afforded the monoamido lanthanide complexes L'(2)LnN(TMS)(2) (Ln = Yb (9), Y (10), Nd (11), and La (12)). While the amine elimination with the less bulky Schiff base HL' (L' = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-2,6-Me(2)-C(6)H(3)) yielded the desired monoamido complexes with the small metals of Y and Yb, L'(2)LnN(TMS)(2) (Ln = Yb (13) and Y (14)), and the more stable tris-Schiff base complexes with the large metals of La and Nd, yielded L'(3)Ln as the only product. Complexes 1-14 were fully characterized including X-ray crystal structural analysis. Complexes 1-5, 10, and 14 can serve as the efficient catalysts for addition of amines to carbodiimides, and the catalytic activity is greatly affected by the lanthanide metals with the active sequence of Yb < Y < Eu ≈ Nd ≈ La.     

Synthesis, crystal structure, and magnetic properties of the first nonanuclear lanthanide(III)-copper(II) complexes of macrocyclic oxamide [NaLn(2)Cu(6)] (macrocyclic oxamide = 1,4,8,11-tetraazacyclotradecanne-2,3-dione, Ln = Pr, Nd)

Two new nonanuclear lanthanide(III)-copper(II) complexes of macrocyclic oxamide [NaPr(2)(CuL)(6)(H(2)O)(6)](ClO(4))(6)Cl small middle dot6H(2)O (1) and [NaNd(2)(CuL)(6)(H(2)O)(6)](ClO(4))(6)Cl small middle dot8H(2)O (2) have been synthesized and characterized by means of elemental analysis, IR, and electronic spectra, where L = 1,4,8,11-tetraazacyclotradecanne-2,3-dione. The crystal structures of the two complexes have been determined. The structures of 1 and 2 consist of nonanuclear cations, perchlorate and chloride anions, and water molecules. In the two complexes, each copper(II) ion is connected to lanthanide(III) ion via the exo-cis oxygen atoms of the oxamido macrocyclic ligands, resulting in a tetranuclear subunit. The sodium ion links two tetranuclear subunits via the exo oxygen atoms of the oxamido macrocyclic ligands which results in a novel nonanuclear complex. The magnetic properties of the two complexes have been investigated. Preliminary treatment of the magnetic data by considering Ln(III) as free ion cannot give reasonable results, and accurate models involving both the orbital contribution and ligand field effect have to be developed.     

直链醚-二甘肽型Schiff碱与稀土新配合物的合成、配 位作用与波谱

合成了稀土与四甘醇醛-二甘肽型Schiff碱(TAGLGL)形成的六种新配合物,在此配体中同时引入了C=N及HN—C＝O基团。经元素分析、光谱等表征,确定该类多核配合物组成为：[Ln3(TAGLGL)(NO3)7]·4H2O(Ln=La,Nd,Sm,Gd,Yb,Y)。以液体1^HNMR谱、固体高分辨^13CNMR等方法,并结合Gd(Ⅲ)配合物的EPR波谱着重探讨了配位作用,配位数和晶体场强等。     

Crystal structures of lanthanide(III) complexes with cyclen derivative bearing three acetate and one methylphosphonate pendants

A series of lanthanide(III) complexes formulated as M[Ln(Hdo3ap)].xH(2)O (M = Li or H and Ln = Tb, Dy, Er, Lu, and Y) with the monophosphonate analogue of H(4)dota, 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic-10-methylphosphonic acid (H(5)do3ap), was prepared in the solid state and studied using X-ray crystallography. All of the structures show that the (Hdo3ap)(4-) anion is octadentate coordinated to a lanthanide(III) ion similarly to the other H(4)dota-like ligands, i.e., forming O(4) and N(4) planes that are parallel and have mutual angle smaller than 3 degrees . The lanthanide(III) ions lie between these planes, closer to the O(4) base than to the N(4) plane. All of the structures present the lanthanide(III) complexes in their twisted-square-antiprismatic (TSA) configuration. Twist angles of the pendants vary in the range between -24 and -30 degrees, and for each complex, they lie in a very narrow region of 1 degree. The coordinated phosphonate oxygen is located slightly above (0.02-0.19 Angstroms) the O(3) plane formed with the coordinated acetates. A water molecule was found to be coordinated only in the terbium(III) and neodymium(III) complexes. The bond distance Tb-O(w) is unusually long (2.678 Angstroms). The O-Ln-O angles decrease from 140 degrees [Nd(III)] to 121 degrees [Lu(III)], thus confirming the increasing steric crowding around the water binding site. A comparison of a number of structures of Ln(III) complexes with DOTA-like ligands shows that the TSA arrangement is flexible. On the other hand, the SA arrangement is rigid, and the derived structural parameters are almost identical for different ligands and lanthanide(III) ions.     

A family of 13 tetranuclear zinc(II)-lanthanide(III) complexes of a [3+3] Schiff-base macrocycle derived from 1,4-diformyl-2,3-dihydroxybenzene

A family of thirteen tetranuclear heterometallic zinc(II)-lanthanide(III) complexes of the hexa-imine macrocycle (L(Pr))(6-), with general formula Zn(II)(3)Ln(III)(L(Pr))(NO(3))(3)·xsolvents (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), were prepared in a one-pot synthesis using a 3:1:3:3 reaction of zinc(II) acetate, the appropriate lanthanide(III) nitrate, the dialdehyde 1,4-diformyl-2,3-dihydroxybenzene (H(2)L(1)) and 1,3-diaminopropane. A hexanuclear homometallic zinc(II) macrocyclic complex [Zn(6)(L(Pr))(OAc)(5)(OH)(H(2)O)]·3H(2)O was obtained using a 2:0:1:1 ratio of the same reagents. A control experiment using a 1:0:1:1 ratio failed to generate the lanthanide-free [Zn(3)(L(Pr))] macrocyclic complex. The reaction of H(2)L(1) and zinc(II) acetate in a 1:1 ratio yielded the pentanuclear homometallic complex of the dialdehyde H(2)L(1), [Zn(5)(L(1))(5)(H(2)O)(6)]·3H(2)O. An X-ray crystal structure determination revealed [Zn(3)(II)Pr(III)(L(Pr))(NO(3))(2)(DMF)(3)](NO(3))·0.9DMF has the large ten-coordinate lanthanide(III) ion bound in the central O(6) site with two bidentate nitrate anions completing the O(10) coordination sphere. The three square pyramidal zinc(II) ions are in the outer N(2)O(2) sites with a fifth donor from DMF. Measurement of the magnetic properties of [Zn(II)(3)Dy(III)(L(Pr))(NO(3))(3)(MeOH)(3)]·4H(2)O with a weak external dc field showed that it has a frequency-dependent out-of-phase component of ac susceptibility, indicative of slow relaxation of the magnetization (SMM behaviour). Likewise, the Er and Yb analogues are field-induced SMMs; the latter is only the second example of a Yb-based SMM. The neodymium, ytterbium and erbium complexes are luminescent in the solid phase, but only the ytterbium and neodymium complexes show strong lanthanide-centred luminescence in DMF solution.     

Oligonuclear 3d-4f complexes as tectons in designing supramolecular solid-state architectures: impact of the nature of linkers on the structural diversity

Heteronuclear cationic complexes, [LCuLn]3+ and [(LCu)2Ln]3+, were employed as nodes in designing high-nuclearity complexes and coordination polymers with a rich variety of network topologies (L is the dianion of the Schiff base resulting from the 2:1 condensation of 3-methoxysalycilaldehyde with 1,3-propanediamine). Two families of linkers have been chosen: the first consists of exo-dentate ligands bearing nitrogen-donor atoms (bipyridine (bipy), dicyanamido (dca)), whereas the second consists of exo-dentate ligands with oxygen-donor atoms (anions derived from the acetylenedicarboxylic (H2acdca), fumaric (H2fum), trimesic (H3trim), and oxalic (H2ox) acids). The ligands belonging to the first family prefer copper(II) ions, whereas the ligands from the second family interact preferentially with oxophilic rare-earth cations. The following complexes have been obtained and crystallographically characterized: [LCu(II)(OH2)Gd(III)(NO3)3] (1), [{LCu(II)Gd(III)(NO3)3}2(mu-4,4'-bipy)] (2), 1infinity[LCu(II)Gd(III)(acdca)(1.5)(H2O)2].13H2O (3), 2infinity[LCu(II)Gd(III)(fum)(1.5)(H2O)2].4H2O.C2H5OH (4), 1infinity[LCu(II)Sm(III)(H2O)(Hfum)(fum)] (5), 1infinity[LCu(II)Er(III)(H2O)2(fum)]NO3.3H2O (6), 2infinity[LCu(II)Sm(III)(fum)(1.5)(H2O)2].4H2O.C2H5OH (7), [{(LCu(II))2Sm(III)}2fum2](OH)2 (8), 1infinity[LCu(II)Gd(III)(trim)(H2O)2].H2O (9), 2infinity[{(LCu(II))2Pr(III)}(C2O4)(0.5)(dca)]dca.2H2O (10), [LCu(II)Gd(III)(ox)(H2O)3][Cr(III)(2,2'-bipy)(ox)2].9H2O (11), and [LCuGd(H2O)4{Cr(CN)6}].3H2O (12). Compound 1 is representative of the whole family of binuclear Cu(II)-Ln(III) complexes which have been used as precursors in constructing heteropolymetallic complexes. The rich variety of the resulting structures is due to several factors: 1) the nature of the donor atoms of the linkers, 2) the preference of the copper(II) ion for nitrogen atoms, 3) the oxophilicity of the lanthanides, 4) the degree of deprotonation of the polycarboxylic acids, 5) the various connectivity modes exhibited by the carboxylato groups, and 6) the stoichiometry of the final products, that is, the Cu(II)/Ln(III)/linker molar ratio. A unique cluster formed by 24 water molecules was found in crystal 11. In compounds 2, 3, 4, 9, and 11 the Cu(II)-Gd(III) exchange interaction was found to be ferromagnetic, with J values in the range of 3.53-8.96 cm(-1). Compound 12 represents a new example of a polynuclear complex containing three different paramagnetic ions. The intranode Cu(II)-Gd(III) ferromagnetic interaction is overwhelmed by the antiferromagnetic interactions occurring between the cyanobridged Gd(III) and Cr(III) ions.