Unequivocal synthetic pathway to heterodinuclear (4f,4f') complexes: magnetic study of relevant (Ln(III), Gd(III)) and (Gd(III), Ln(III)) complexes

The tripodal ligand tris[4-(2-hydroxy-3-methoxyphenyl)-3-aza-3-buten]amine (LH(3)) is capable of coordinating to two different lanthanide ions to give complexes formulated as [LLnLn'(NO(3))(3)].x H(2)O. The stepwise synthetic procedure consists of introducing first a Ln(III) ion in the inner N(4)O(3) coordination site. The isolated neutral complex LLn is then allowed to react with a second and different Ln' ion that occupies the outer O(6) site, thus yielding a [LLnLn'(NO(3))(3)].x H(2)O complex. A FAB(+) study has confirmed the existence of (Ln, Ln') entities as genuine, when the Ln' ion in the outer site has a larger ionic radius than the Ln ion in the inner site. The qualitative magnetic study of the (Gd, Ln) and (Ln, Gd) complexes, based on the comparison of the magnetic properties of (Gd, Ln) (or (Ln, Gd)) pairs and (Y, Ln) (or (Ln, La)) pairs, is very informative. Indeed, these former complexes are governed by the thermal population of the Ln(III) Stark levels and the Ln-Gd interaction, while the latter are influenced by the thermal population of the Ln(III) Stark levels. We have been able to show that a ferromagnetic interaction exists at low temperature in the (Gd, Nd), (Gd, Ce), and (Yb, Gd) complexes. In contrast, an antiferromagnetic interaction occurs in the (Dy, Gd) and (Er, Gd) complexes. Although we cannot give a quantitative value to these interactions, we can affirm that their magnitudes are weak since they are only perceptible at very low temperature.     

Using the flexible ligand bis(2-hydroxyethyl)amino-tris (hydroxymethyl)methane ("bis-tris") to access a family of 3d-4f Mn(III)4Ln4 complexes

A series of isostructural 3d-4f coordination clusters (CCs) [Mn(4)Ln(4)(OH)(6)(H(2)L)(2)(H(3)L)(2)(PhCO(2))(2)(N(3))(2)(MeOH)(4)]Cl(1.6)(N(3))(0.4)(NO(3))(2)·2.4H(2)O·1.6MeOH where Ln = Gd, Tb, Dy, Ho and Er and H(5)L = bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane (bis-tris) has been synthesised and structurally characterised. The paramagnetic metal ions within the clusters are weakly antiferromagnetically coupled, with the Tb and Dy compounds displaying slow relaxation of their magnetisation. This is the first report of this versatile ligand being used to target 3d-4f CCs.     

Nitrate-Bridged "Pseudo-Double-Propeller"-Type Lanthanide(III)-Copper(II) Heterometallic Clusters: Syntheses, Structures, and Magnetic Properties

Two discrete nitrate-bridged novel "pseudo-double-propeller"-shaped hexanuclear Cu/Ln clusters of the formula [Cu(4)Ln(2)L(4)L'(4)(NO(3))(2)(OH(2))(2)]·3NO(3)·4H(2)O [Ln = Dy, Gd; LH = o-vanilin; L'H = 2-(hydroxyethyl)pyridine] were synthesized and characterized. Single-crystal X-ray diffraction studies revealed the trimeric half-propeller-type Cu(2)/Ln core connected to other opposite-handed similar trimers by a bridging nitrate ligand. The Dy analogue, [Cu(4)Dy(2)L(4)L'(4)(NO(3))(2)(OH(2))(2)]·3NO(3)·4H(2)O, shows frequency-dependent out-of-phase alternating-current magnetic susceptibility, which indicates that this novel discrete [Cu(4)Dy(2)] heterometallic cluster may exhibit single-molecule-magnet behavior.     

Two three-dimensional 2p-3d-4f heterometallic frameworks featuring a Ln6Cu24Na12 cluster as a node

Two three-dimensional 2p-3d-4f heterometallic frameworks featuring a nanosized Ln(6)Cu(24)Na(12) (Ln = Gd, Dy) cluster as a node have been obtained under microwave irradiation conditions through the reaction of H(2)ANMA (H(2)ANMA = L-alanine-N-monoacetic acid), Cu(NO(3))(2), and Ln(NO(3))(3) (Ln = Gd for 1, Dy for 2) with NaOH in deionized water. Investigations on the magnetic properties show that 1 exhibits ferrimagnetic behavior. The electrical conductivity measurements reveal that 1 behaves as a proton conductor.     

Study of the luminescent and magnetic properties of a series of heterodinuclear [Zn(II)Ln(III)] complexes

Herein, we report the synthesis, structural investigation, and magnetic and photophysical properties of a series of 13 [Zn(II)Ln(III)] heterodinuclear complexes, which have been obtained employing a Schiff-base compartmental ligand derived from o-vanillin [H(2)valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol)]. The complexes have been synthesized starting from the [Zn(valpn)(H(2)O)] mononuclear compound and the corresponding lanthanide nitrates. The crystallographic investigation indicated two structural types: the first one, [Zn(H(2)O)(valpn)Ln(III)(O(2)NO)(3)], contains 10-coordinated Ln(III) ions, while in the second one, [Zn(ONO(2))(valpn)Ln(III)(H(2)O)(O(2)NO)(2)]·2H(2)O, the rare earth ions are nine-coordinated. The Zn(II) ions always display a square-pyramidal geometry. The first structural type encompasses the larger Ln ions (4f(0)-4f(9)), while the second is found for the smaller ions (4f(8)-4f(11)). The dysprosium derivative crystallizes in both forms. Luminescence studies for the heterodinuclear compounds containing Nd(III), Sm(III), Tb(III), Dy(III), and Yb(III) revealed that the [Zn(valpn)(H(2)O)] moiety acts as an antenna. The magnetic properties for the paramagnetic [Zn(II)Ln(III)] complexes have been investigated.     

Cooperative processes governing formation of small pentanuclear lanthanide(III) nanoclusters and energy transport within and between them

Syntheses, lanthanide quantitative analyses, mass spectrometry and luminescence spectroscopy, and decay dynamics of crystals containing pentanuclear hetero-lanthanide(III) nanoclusters [(Ln'(5-x)Ln(x))(NO(3))(6)(mu(5)-OH)(mu(4)-L)(2)] (0 < or = x < or = 5), Ln' = Eu or Tb; Ln = La-Nd, Sm-Ho (hereafter Ln'(5-x) Ln(x)) were undertaken in search of information on factors governing self-assembly processes by which the clusters are formed and electronic interactions within and between them. The data obtained are consistent with the self-assembly of Ln'(5-x) Ln(x) nanoclusters being a concerted process featuring a profound expression of complementarity among mutually bridging [Ln(mu(4)-L](-) and [Ln(NO(3))(2)](+) components. The energy transport regime in crystals of Eu(5-x) Ln(x) is in the dynamic regime when x = 0 or Ln = La and, at 293 K, Ln = Dy, despite the presence of two crystallographically different Eu(3+) coordination environments which give rise to a doublet in the excitation and emission spectra of Eu(3+)((5)D(0)). The luminescence decay behavior of Eu(3+)((5)D(0)) in Eu(5-x) Ln(x) (Ln = Dy (for 77 K), Sm) is intermediate between the static and dynamic limits and reveals extensive electronic coupling among lanthanide ions, including many-body processes at relatively high Dy(3+) or Sm(3+) concentrations.     

Luminescence tuning of imidazole-based lanthanide(III) complexes [Ln = Sm, Eu, Gd, Tb, Dy

To tune the lanthanide luminescence in related molecular structures, we synthesized and characterized a series of lanthanide complexes with imidazole-based ligands: two tripodal ligands, tris{[2-{(1-methylimidazol-2-yl)methylidene}amino]ethyl}amine (Me(3)L), and tris{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(3)L), and the dipodal ligand bis{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(2)L). The general formulas are [Ln(Me(3)L)(H(2)O)(2)](NO(3))(3)·3H(2)O (Ln = 3+ lanthanide ion: Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)), [Ln(H(3)L)(NO(3))](NO(3))(2)·MeOH (Ln(3+) = Sm (6), Eu (7), Gd (8), Tb (9), and Dy (10)), and [Ln(H(2)L)(NO(3))(2)(MeOH)](NO(3))·MeOH (Ln(3+) = Sm (11), Eu (12), Gd (13), Tb (14), and Dy (15)). Each lanthanide ion is 9-coordinate in the complexes with the Me(3)L and H(3)L ligands and 10-coordinate in the complexes with the H(2)L ligand, in which counter anion and solvent molecules are also coordinated. The complexes show a screw arrangement of ligands around the lanthanide ions, and their enantiomorphs form racemate crystals. Luminescence studies have been carried out on the solid and solution-state samples. The triplet energy levels of Me(3)L, H(3)L, and H(2)L are 21?000, 22?700, and 23?000 cm(-1), respectively, which were determined from the phosphorescence spectra of their Gd(3+) complexes. The Me(3)L ligand is an effective sensitizer for Sm(3+) and Eu(3+) ions. Efficient luminescence of Sm(3+), Eu(3+), Tb(3+), and Dy(3+) ions was observed in complexes with the H(3)L and H(2)L ligands. Ligand modification by changing imidazole groups alters their triplet energy, and results in different sensitizing ability towards lanthanide ions.     

Planar tetranuclear lanthanide clusters with the Dy4 analogue displaying slow magnetic relaxation

Two isostructural tetranuclear lanthanide clusters of general formula [Ln(III)(4)(μ(3)-OH)(2)(o-van)(4)(O(2)CC(CH(3))(3))(4)(NO(3))(2)]·CH(2)Cl(2)·1.5H(2)O (Ln = Gd (1) and Dy (2)) (o-van = 3-methoxysalicylaldehydato anion) are reported. The metallic cores of both complexes display a planar 'butterfly' arrangement. Magnetic studies show that both are weakly coupled, with 2 displaying probable SMM behaviour.     

Synthesis, structures, and luminescence properties of lanthanide complexes with structurally related new tetrapodal ligands featuring salicylamide pendant arms

To explore the relationships between the structures of ligands and their complexes, we have synthesized and characterized a series of lanthanide complexes with two structurally related ligands, 1,1,1,1-tetrakis{[(2'-(2-benzylaminoformyl))phenoxyl]methyl}methane (L(I)) and 1,1,1,1-tetrakis{[(2'-(2-picolyaminoformyl))phenoxyl]methyl}methane (L(II)). A series of zero- to three-dimensional lanthanide coordination complexes have been obtained by changing the substituents on the Pentaerythritol. Our results revealed that, complexes of the L(I) ligand, {Ln(4)L(I)(3)(NO(3))(12).nC(4)H(10)O}(infinity) (Ln = Nd, Eu, Tb, Er, n = 3 or 6)] show the binodal 3,4-connected three-dimensional interpenetration coordination polymers with topology of a (8(3))(4)(8(6))(3) notation. Compared to L(I), complexes of L(II) present a cage-like homodinuclear [Ln(2)L(II)(2)(NO(3))(6).2H(2)O].nH(2)O (Ln = Nd, Tb, Dy, n = 0 or 1) or a helical one-dimensional coordination {[ErL(II)(NO(3))(3).H(2)O].H(2)O}(infinity) polymer. The luminescence properties of the resulting complexes formed with ions used in fluoroimmunoassays (Ln = Eu, Tb) are also studied in detail. It is noteworthy that subtle variation of the terminal group from benzene to pyridine not only sensibly affects the overall molecular structures but also the luminescence properties as well.     

Structure, magnetism and theory of a family of nonanuclear Cu(II)5Ln(III)4-triethanolamine clusters displaying single-molecule magnet behaviour

Synthesis, crystal structures and magnetic studies are reported for four new heterometallic Cu(II)-Ln(III) clusters. The reaction of Cu(NO(3))(2)·3H(2)O with triethanolamine (teaH(3)), pivalic acid, triethylamine and Ln(NO(3))(3)·6H(2)O (Ln=Gd, Tb, Dy and Ho) results in the formation of four isostructural nonanuclear complexes of general formula [Cu(II)(5)Ln(III)(4)O(2)(teaH)(4){O(2)CC(CH(3))(3)}(2)(NO(3))(4)(OMe)(4)]·2MeOH·2Et(2)O [Ln=Gd (1), Tb (2), Dy (3) and Ho (4)]. The metal core of each cluster is made up of four face- and vertex-sharing tetrahedral units. Solid-state DC magnetic susceptibility studies reveal competing anti- and ferromagnetic interactions within each cluster leading to large-spin ground states for 1-4. Solid-state AC magnetic susceptibility studies show frequency-dependent out-of-phase (χ'(M)) signals for 2-4 below 4 K, suggestive of single-molecule magnet behaviour. Ab initio calculations on one of the anisotropic examples (3) provided a rare set of J values for Dy-Cu and Cu-Cu exchange interactions (Dy-Dy zero), some ferro- and some antiferromagnetic in character, that explain its magnetic behaviour.     

Structural and photophysical properties of heterobimetallic 4f-zn iminophenolate cryptates

Lanthanide complexes with the Schiff base axial macrobicyclic ligand L(1) react with Zn(II) nitrate in the presence of CaH(2) to yield Ln(III)-Zn(II) heterodinuclear cryptates with the formula [Ln(NO(3))(L(1)-3H)Zn](NO(3)).xH(2)O.yMeOH. The macrobicyclic receptor L(1) is an azacryptand N[(CH(2))(2)N=CH-R-CH=N-(CH(2))(2)](3)N (R = 1,3-(2-OH-5-Me-C(6)H(2))). The crystal structures of the Pr(III), Yb(III), and Lu(III) complexes, chemical formulas [Ln(NO(3))(L(1)-3H)Zn](NO(3)).xSolv (monoclinic, C2/c, Z = 8), as well as that of [Zn(2)(L(1)-3H)](NO(3)).H(2)O (15) (triclinic, P(-)1, Z = 2), have been determined by X-ray crystallography. The ligand is helically wrapped around the two metal ions, leading to pseudo-C(3) symmetries around the metals. The Ln(III)-Zn(II) distances lie in the range 3.3252(13) to 3.2699(14) A, while the Zn(II)-Zn(II) distance in 15 amounts to 3.1037(18) A. The three five-membered chelate rings of the ligand backbone coordinating the Ln(III) ion adopt a (lambdalambdadelta)(5) (or (deltadeltalambda)(5)) conformation while the three pseudochelate rings formed by the coordination of the ligand to the Zn(II) ion adopt a (lambda'lambda'lambda')(5) (or (delta'delta'delta')(5)) conformation. Thus in the solid state the conformation of the three cations is Lambda(deltadeltalambda)(5)(delta'delta'delta')(5) or its enantiomeric form Delta(lambdalambdadelta)(5)(lambda'lambda'lambda')(5). In solution, the helicates present a time-averaged C(3) symmetry, as shown by (1)H NMR, and the conformation of the cations is described as Lambda(deltadeltadelta)(5)(delta'delta'delta')(5) (or Delta(lambdalambdalambda)(5)(lambda'lambda'lambda')(5)). The photophysical properties of the cryptates depend on the nature of the Ln(III) ion, and (L-3H)(3)(-) is revealed to be a good sensitizer for Eu(III) and Tb(III) at low temperatures, but the emission at room temperature is limited by the low energy of the ligand (3)pipi state. While Eu(III) is most effectively sensitized by the ligand triplet state, the Tb(III) ((5)D(4)) sensitization occurs via the singlet state. The quantum yield of the metal-centered luminescence in the Eu-Zn cryptate amounts to 1.05% upon ligand excitation. The low energy of the ligand (3)pipi state allows efficient sensitization of the Nd(III) and Yb(III) cryptates, which emit in the near-infrared.     

Synthesis, characterisation and biological evaluation of lanthanide(III) complexes with 3-acetylcoumarin-o-aminobenzoylhydrazone (ACAB)

Lanthanide(III) complexes of the general formula [Ln(ACAB)(2)(NO(3))(2)(H(2)O)(2)].NO(3).H(2)O where Ln=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III), ACAB=3-acetylcoumarin-o-aminobenzoylhydrazone have been isolated and characterised based on elemental analyses, molar conductance, IR, (1)H- and (13)C-NMR, UV, TG/DTA and EPR spectral studies. The ligand behaves in bidentate fashion coordinating through hydrazide >C=O and nitrogen of >C=N. A coordination number of ten is assigned to the complexes. Antibacterial and Antifungal studies indicate an enhancement of activity of the ligand on complexation.     

A series of 3d-4f heterometallic frameworks comprising 2D lanthanide-organic layers and diverse Cu-complex pillars

Six novel 3D layer-pillared lanthanide-transition metal coordination polymers,LnCuX(IN)2(Ac)(H2O)(Ln = Tb,X = Br(1);Ln = Er,X = Cl(2)),[LnCuCl(IN)2(Ac)].H2O(Ln = Gd(3);Ln = Eu(4)),and [LnCu2Br2(IN)2(Ac)(H2O)].nH2O(Ln = Dy,n =0(5);Ln = Gd,n = 0.5(6))(IN = isonicotinate,Ac = acetate),have been obtained by linking Ln-organic layers and diverse Cu-complex pillars under hydrothermal conditions.1 and 2 are isostructural and formed by 2D Ln-IN-Ac layers and CuX(IN)2 pillars(X = Br(1),X= Cl(2));3 and 4 are isomorph...     

Structural,electrical, and magnetic properties of a series of molecular conductors based on BDT-TTP and lanthanoid nitrate complex anions (BDT-TTP = 2,5-Bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene)

The platelike crystals of a series of novel molecular conductors, which are based on the pi-donor molecules BDT-TTP (2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene) with a tetrathiapentalene skeleton and lanthanide nitrate complex anions [Ln(NO3)x](3-x)(Ln = La, Ce, (Pr), Tb, Dy, Ho, Er, Tm, Yb, Lu) with localized 4f magnetic moments, were synthesized. Except for the Ce complex, the salts were composed of (BDT-TTP)(5)[Ln(NO(3))(5)] and were isostructural. Even though the Ce crystal had a different composition, (BDT-TTP)(6)[Ce(NO(3))(6)](C(2)H(5)OH)(x)() (x approximately 3), the crystals all had the space group P(-)1. Although the X-ray examination of the Pr salts was insufficient, the existence of two modifications was suggested in these systems by preliminary X-ray examination. Previously, we reported the crystal structures and unique magnetic properties of (BDT-TTP)(5)[Ln(NO(3))(5)] (Ln = Sm, Eu, Nd, Gd). Thus, by combining the results of this work with previous one, we for the first time succeeded in obtaining a complete set of organic conductors composed of the identical pi-donors (BDT-TTP in this case) and all the lanthanide nitrate complex anions (except the complex with Pm(3+)). The crystals were all metallic down to 2 K. Electronic band structure calculations resulted in two-dimensional Fermi surfaces, which was consistent with their stable metallic states. Except for the Lu complex, which lacked paramagnetic moments, the magnetic susceptibilities were measured on the six heavy lanthanide ion complex salts by a SQUID magnetometer (Ln = Tb, Dy, Ho, Er, Tm, Yb). The large paramagnetic susceptibilities, which were caused by the paramagnetic moments of the rare-earth ions, were obtained. The Curie-Weiss law fairly accurately reproduced the temperature dependence of the magnetic susceptibilities of (BDT-TTP)(5)[Ho(NO(3))(5)] in the experimental temperature range (2-300 K) and a comparatively large Weiss temperature (|THETAV;|) was obtained (THETAV;(Ho) = -15 K). A Weiss temperature (THETAV;(Tm) = -8 K) was also obtained for Tm. The |THETAV;| values of other (BDT-TTP)(5)[Ln(NO(3))(5)] salts and (BDT-TTP)(6)[Ce(NO(3))(6)](C(2)H(5)OH)x(x approximately 3) were as follows: |THETAV;|/K = 4 (Er), < or =2 (Ce, Tb, Dy, Yb). The comparatively strong intermolecular magnetic interaction between Ho(3+) ions, which was suggested by the |THETAV;| value, is inconsistent with the traditional image of strongly localized 4f orbitals shielded by the electrons in the outer 5s and 5p orbitals. The dipole interactions between Ln(3+) ions causing the Curie-Weiss behavior and the comparatively large THETAV; value of (BDT-TTP)(5)[Ho(NO(3))(5)] is inconsistent with the data, since the complexes exhibit isostructural properties and there is not a clear relationship between the magnitudes of THETAV; values and those of magnetic moments. Therefore, it is possible that the 4f orbitals of Ho atom are sensitive to the ligand field, which will have an effect on the orbital moment of the Ho(3+) ion and/or produce a small amount of mixing between 4f and ligand orbitals to give rise to "real" intermolecular antiferromagnetic interaction through intermolecular overlapping between pi (BDT-TTP) and ligand orbitals of lanthanide nitrate complex anions.     

Complexes of lanthanide nitrates with bis(diphenylphosphino)methane dioxide

The reactions of lanthanide nitrates, Ln(NO(3))(3), with bis(diphenylphosphino)methane dioxide, Ph(2)P(O)CH(2)P(O)Ph(2) (L), lead to complexes with three distinct classes of structure. At low ratios of Ln:L (<1:1.5) in acetonitrile the ionic complexes [Ln(NO(3))(2)L(2)](+)[Ln(NO(3))(4)L](-) (Ln = Pr, Eu) have been isolated. When carried out with a 1:2 or higher ratio in ethanol the reaction yields Ln(NO(3))(3)L(2) (Ln = La,Ce) and [Ln(NO(3))(2)L(2)H(2)O](+)[NO(3)](-) (Ln = Nd, Gd, Ho). Geometrical isomerism is found for the cations [Ln(NO(3))(2)L(2)H(2)O](+) and is attributed to the extent of hydrogen bonding to the coordinated water. Ligand redistribution occurs on heating in the solid state giving yellow solids in all cases. Crystallization of these materials from ethanol or acetonitrile gives [Ln(NO(3))L(3)](2+).2[NO(3)](-), which have been structurally characterized for Ln = Gd and Yb. Electrospray mass spectra indicate that extensive ligand exchange reactions occur in solution.     

Fluoride bridges as structure-directing motifs in 3d-4f cluster chemistry

The use of kinetically robust chromium(III) fluorido complexes as synthons for mixed 3d-4f clusters is reported. The tendency toward linear {Cr(III)-F-Ln(III)} units dictates the cluster topology. Specifically, we show that reaction of cis-[Cr(III)F(2)(NN)(2)]NO(3) (NN = 1,10-phenanthroline ("phen") or 2,2'-bipyridine ("bpy")) with Ln(NO(3))(3)·xH(2)O produces isostructural series of molecular {Ln(2)Cr(2)} squares (1-9) with linear fluoride bridges. In a parallel fashion, fac-[Cr(III)F(3)L], where L = N,N',N″-trimethyl-1,4,7-triazacyclononane ("Me(3)tacn"), reacts with Nd(NO(3))(3)·6H(2)O to form a fluoride-centered penta-nuclear complex and fac-[Cr(III)F(3)L'], with L' = 1,1,1-tris-((methylamino)methylethane) ("Me(3)tame"), reacts with [Ln(hfac)(3)(H(2)O)(2)] (hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone) to yield an isostructural series of {Ln(3)Cr(2)} (10-14) trigonal bipyramids with no central ligand. The formation of the latter is accompanied by a partial solvolysis of the Cr(III) precursor but without formation of insoluble LnF(3). The magnetic properties of the gadolinium containing clusters allow quantification of fluoride-mediated, antiferromagnetic Gd-Cr exchange interactions of magnitude between 0.14 cm(-1) and 0.71 cm(-1) (? = J(12)?(1)·?(2) formalism) and vanishingly small J(Gd-Gd) of 0.06(0) cm(-1). The large spin and small anisotropy together with weak exchange interactions in the {Gd(3)Cr(2)} (11) cluster give rise to a very large magneto-caloric effect of -ΔS(m) = 28.7 J kg(-1) K(-1) (μ(0)H = 90 to 0 kOe).     

Family of carboxylate- and nitrate-diphenoxo triply bridged dinuclear Ni(II)Ln(III) complexes (Ln = Eu, Gd, Tb, Ho, Er, Y): synthesis, experimental and theoretical magneto-structural studies, and single-molecule magnet behavior

Seven acetate-diphenoxo triply bridged M(II)-Ln(III) complexes (M(II) = Ni(II) and Ln(III) = Gd, Tb, Ho, Er, and Y; M(II) = Zn(II) and Ln(III) = Ho(III) and Er(III)) of formula [M(μ-L)(μ-OAc)Ln(NO(3))(2)], one nitrate-diphenoxo triply bridged Ni(II)-Tb(III) complex, [Ni(μ-L)(μ-NO(3))Tb(NO(3))(2)]·2CH(3)OH, and two diphenoxo doubly bridged Ni(II)-Ln(III) complexes (Ln(III) = Eu, Gd) of formula [Ni(H(2)O)(μ-L)Ln(NO(3))(3)]·2CH(3)OH have been prepared in one pot reaction from the compartmental ligand N,N',N"-trimethyl-N,N"-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H(2)L). Moreover, Ni(II)-Ln(III) complexes bearing benzoate or 9-anthracenecarboxylate bridging groups of formula [Ni(μ-L)(μ-BzO)Dy(NO(3))(2)] and [Ni(μ-L)(μ-9-An)Dy(9-An)(NO(3))(2)]·3CH(3)CN have also been successfully synthesized. In acetate-diphenoxo triply bridged complexes, the acetate bridging group forces the structure to be folded with an average hinge angle in the M(μ-O(2))Ln bridging fragment of ~22°, whereas nitrate-diphenoxo doubly bridged complexes and diphenoxo-doubly bridged complexes exhibit more planar structures with hinge angles of ~13° and ~2°, respectively. All Ni(II)-Ln(III) complexes exhibit ferromagnetic interactions between Ni(II) and Ln(III) ions and, in the case of the Gd(III) complexes, the J(NiGd) coupling increases weakly but significantly with the planarity of the M-(O)(2)-Gd bridging fragment and with the increase of the Ni-O-Gd angle. Density functional theory (DFT) theoretical calculations on the Ni(II)Gd(III) complexes and model compounds support these magneto-structural correlations as well as the experimental J(NiGd) values, which were found to be ~1.38 and ~2.1 cm(-1) for the folded [Ni(μ-L)(μ-OAc)Gd(NO(3))(2)] and planar [Ni(H(2)O)(μ-L)Gd(NO(3))(3)]·2CH(3)OH complexes, respectively. The Ni(II)Dy(III) complexes exhibit slow relaxation of the magnetization with Δ/k(B) energy barriers under 1000 Oe applied magnetic fields of 9.2 and 10.1 K for [Ni(μ-L)(μ-BzO)Dy(NO(3))(2)] and [Ni(μ-L)(μ-9-An)Dy(9-An)(NO(3))(2)]·3CH(3)CN, respectively.     

New Cd(II)-, Co(II)-, and Cu(II)-containing coordination polymers synthesized by using the rigid ligand 1,2-bis(3-pyridyl)ethyne (3,3'-DPA)

Four new organic/inorganic coordination polymers, [Cd(C(10)H(8)N(2))(2)(H(2)O)(2)(NO(3))(2)](n)(1), [Co(C(10)H(8)N(2))(H(2)O)NO(3)CH(3)OH](n)(2), [Cu(C(10)H(8)N(2))(CH(3)OH)(NO(3))(2)](n) (3), and [Cu(C(10)H(8)N(2))(hfac)(2)](n)(4), were synthesized by using the rigid ligand 1,2-bis(3-pyridyl)ethyne (3,3'-DPA). Complex 1 crystallizes in space group P2/n: a = 12.462(2) A, b = 9.485(1) A, c = 13.383(2) A, beta = 96.629(2) degrees, V = 1559.6(3) A(3), Z = 4. Complex 2 crystallizes in space group Fddd: a = 9.248(4) A, b = 19.982(7) A, c = 35.093(16) A, V = 6485.0(4) A(3), Z = 8. Complex 3 crystallizes in space group I2/a: a = 18.315(2) A, b = 8.517(1) A, c = 20.494(3) A, beta = 104.042(2) degrees, V = 3101.2(7) A(3), Z = 8. Complex 4 crystallizes in space group P21/c: a = 6.576(1) A, b = 16.189(1) A, c = 11.653(1) A, beta = 91.337(1) degrees, V = 1240.3(2) A(3), Z = 2. The coordination polymers display a variety of structural architectures, ranging from sinusoidal and zigzag chains (1, 3, 4) to two-dimensional channel-type architectures (2). The effects of the orientation of the nitrogen atom in the pyridine rings on the resultant structures are discussed.     

A tetranuclear, macrocyclic 3d-4f complex showing single-molecule magnet behavior

[Cu(II)(3)Tb(III)(L(Pr))(NO(3))(2)(MeOH)(H(2)O)(2)](NO(3))·3H(2)O is a rare example of a 3d-4f single-molecule magnet prepared using a macrocyclic ligand: at low T, it exhibits frequency-dependent alternating-current susceptibility, indicative of slow relaxation of the magnetization.     

Organic-inorganic hybrid materials constructed from inorganic lanthanide sulfate skeletons and organic 4,5-imidazoledicarboxylic acid

Five different types of the lanthanide sulfate-carboxylates family, [La(2)(SO(4))(Himdc)(2)(H2O)2] , [Gd(2)(SO(4))(2)(Himdc)(H2O)3].H2O , [Ln(2)(SO(4))(2)(Himdc)(H2O)(3)].H2O (Ln = Gd3a, Eu3b), [Eu(6)Cu(SO(4))(6)(Himdc)(4)(H2O)(14)] , and [Ln(Himc)(SO(4))(H2O)] (Ln = Eu5a, Gd5b, Tb5c, Dy5d, Er5e); H(2)imc = 4-imidazolecarboxylic acid, H(3)imdc = 4,5-imidazoledicarboxylic acid) have been obtained by hydrothermal reactions of Ln(2)O(3), transition metal sulfates and H(3)imdc at 170 degrees C and characterized by means of elemental analyses, IR, TG analysis, luminescence spectroscopy and single crystal X-ray diffraction. The 3D structure of 1 is constructed from alternately linkages of organic {La(Himdc)} layers and inorganic {La(2)O(2)(SO(4))} layers, with the La atoms as hinges. 2 and 3a/3b both contain alternately arranged 1D left- and right-handed helical {Ln(imdc)} chains bridged by SO(4)(2-) anions to form a 3D framework with 1D rectangle-like channels along the b axis. The structural differences of 2 and 3a/3b lie in the linkages of the SO(4)(2-) anions. Complex 4 consists of 2D tubular Eu-sulfate layers pillared by {Cu(Himdc)(2)} units to generate a 3D network. Complexes 5a-5e possess 2D bamboo-raft-like layer structures based on helical tubes. Interestingly, H(2)imc comes from the in-situ decarboxylation of H(3)imdc in the hydrothermal reactions. The luminescence properties of the complexes 3a, 4, 5a 5c, 5d were investigated in solid state at room temperature.