Some lanthanide metal complexes of n-isonicotinamidosalicylaldimine

Trivalent lanthanide complexes of the type K[ML ₂] whereM=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III) and Dy(III) and H₂ L=N-isonicotinamidosalicyladimine, have been prepared and characterised. The nephelauxetic ratio (β), covalency (δ) and bonding parameter (b ²) of K[NdL ₂] have been calculated. Infrared spectral studies reveal that N-isonicotinamidosalicylaldimine acts as a dibasic tridentate ligand. A coordination number six has been proposed for the lanthanide metal ions.     

Nicotinoyl hydrazide complexes of some first row transition metal ions

Summary Nicotinoyl hydrazide, L, complexes of the MLCl₂ · n EtOH type [M = manganese(II), iron(ll), cobalt(II), nickel(II) and copper(II); n = 0 or 1], WL₂) (NO₃)₂ [M = cobalt(II) and nickel(II)] and mixed metal complexes such as HgCo₂ L₂ Cl₆ and (NiL₂)HgI₄ have been prepared and their nature and structure studied by molar conductance, magnetic susceptibility, electronic, e.s.r. and i.r. spectral measurements. Octahedral structures have been proposed for all the complexes except MnLCl₂, CoLCl₂ and HgCo₂ L₂ C1₆ for which tetrahedral geometry is suggested.     

Transition metal complexes of isonicotinic acid (2-hydroxybenzylidene)hydrazide

A new series of transition metal complexes of Schiff base isonicotinic acid (2-hydroxybenzylidene)hydrazide, HL, have been synthesized. The Schiff base reacted with Cu(II), Ni(II), Co(II), Mn(II), Fe(III) and UO2(II) ions as monobasic tridentate ligand to yield mononuclear complexes of 1:2 (metal:ligand) except that of Cu(II) which form complex of 1:1 (metal:ligand). The ligand and its metal complexes were characterized by elemental analyses, IR, UV-vis, mass and 1H NMR spectra, as well as magnetic moment, conductance measurements, and thermal analyses. All complexes have octahedral configurations except Cu(II) complex which has an extra square planar geometry distorted towards tetrahedral. While, the UO2(II) complex has its favour hepta-coordination. The ligand and its metal complexes were tested against one strain Gram +ve bacteria (Staphylococcus aureus), Gram -ve bacteria (Escherichia coli), and Fungi (Candida albicans). The tested compounds exhibited higher antibacterial activities.     

Synthesis and fluorescent properties of bis-salicyloyl hydrazide metal complexes of some group IV ions

Four novel organometallic compounds containing tin(IV), titanium(IV) and zirconium (IV) ions were synthesized and strong fluorescent emission was observed from two tin(IV) complexes.     

Metal complexes of isonicotinic acid hydrazide

Complexes of platinum(IV), ruthenium(III), rhodium(III), iridium(III), gold(III), dioxouranium(II), zinc(II), cadmium(II), mercury(II) and manganese(II) with isonicotinic acid hydrazide were prepared and characterized on the basis of analytical, conductometric, magnetic susceptibility and spectral data. Platinum(IV) ruthenium(III), rhodium(III), iridium(III), dioxouranium(II) and manganese(II) form six-coordinate complexes while gold(III), zinc(II), cadmium(II) and mercury(II) form four coordinate complexes.     

Two isostructural triboluminescent lanthanide complexes

(4‐Di­methyl­amino­pyridine)­tris(2,2,6,6‐tetra­methyl­heptane‐3,5‐dionato)­terbium(III), [Tb(C₁₁H₁₉O₂)₃(C₇H₁₀N₂)], and its samarium analogue, [Sm(C₁₁H₁₉O₂)₃(C₇H₁₀N₂)], are isostructural. Their polar space group is consistent with observed second harmonic generation and with the involvement of piezoelectric charging in their intense triboluminescence properties, which are of interest for the development of damage sensors in composite materials. The metals display irregular seven‐coordination by one substituted pyridine and three chelating diketonate ligands, bond lengths to Tb being shorter than those to Sm.     

Adjustment of twist angles in pseudo-helical lanthanide complexes by the size of metal ions

Control of self-assembled nanostructures is a promising technique for nanotechnology. We have examined as to whether nanostructures could be controlled by the size of the central metal ion. Lanthanides are a natural choice for such a study as the size of their trivalent ions changes with atomic number gradually. For this investigation, a series of rare earth complexes ([LaL(1)], [CeL(1)], [SmL(1)], [TbL(1)], [YL(1)], and [LuL(1)]) with a tripodal heptadentate ligand L(1) were synthesized, and their X-ray crystallographic analysis was performed. Although the structures of the ligand (H(3)L(1)) and of the metal complex ([ML(1)]) were quite different, all complexes were almost isostructural pseudohelices. The result of the crystallographic studies demonstrated that the twist angles of helices in the complexes depend on the ionic size of the central metal. A detailed analysis helped determine which portion of the helical strand contributed to the total helicity, and the major cause for the difference in helicity among the lanthanides is discussed. Moreover, this result is the first example showing that La(I) (II) and Lu(I) (II) complexes with the same tripodal heptadentate ligand are isostractural.     

Polymerization of lanthanide acrylonitrile complexes

The molecular complexes of some lanthanides scandium (Sc3+), yttrium (Y3+), lanthanum (La3+), gadolinium (Gd3+), cerium (Ce3+) and ytterbium (Yb3) have been studies in dimethyl formamide (DMF) spectrophtometrically equilibrium constants (K), molar extintion coefficient (epsilon), energy of transition (E) and free energy (delta G*) were calculated. The polymerization of acrylonitrile has been studied and investigated in the presence of Sc3+, Y3+, La3+, Gd3+, Ce3+, and Yb3+ ions. The IR spectra of the formed AN-M (III) Br3 polymer complexes show the absence of the C identical to N band and the presence of two new bands corresponding to NH2 and OH groups. Magnetic moment values and the thermal stabilities of homopolymer and the polymer complexes were studied by means of thermogravimetric analysis and the activation energies for degradation were calculated.     

Thermolysis of lanthanide dithiocarbamate complexes

Polycrystalline lanthanide sulfide materials were formed at low temperatures using a single-source precursor based on the lanthanide dithiocarbamate complex. The synthesis temperatures are generally lower than standard solid state preparations, avoid toxic sulfurizing gases and provide a convenient route to prepare lanthanide chalcogenide nanoparticles. Depending on the reaction conditions and oxophilicity of the lanthanide, the sulfide material was formed with oxidized products including oxysulfides, oxysulfates and the oxide.     

Polymetallic lanthanide complexes with PAMAM-naphthalimide dendritic ligands: luminescent lanthanide complexes formed in solution

Generation 3 PAMAM dendrimers functionalized with 2,3-naphthalimide chromophoric groups on the end branches were synthesized, and the formation of Eu3+ polymetallic complexes was investigated. The luminescence properties of these complexes upon binding were fully characterized. On addition of Eu3+ to the dendrimer solution, lanthanide luminescence appears. The formation of a luminescent species corresponding to a dendrimer:lanthanide ratio of 1:8 was determined by luminescence batch titration and indicated by the maximum of Eu3+ emission. This indicates an overall average coordination number of 7.5 around each lanthanide metal cation. This is the first report of such characterization in the literature. Luminescence lifetimes indicate that the metal cation is well protected from nonradiative deactivation by the dendritic structure. Despite the limited efficiency of the sensitization of Eu3+, the absolute quantum yield being 0.0006, the good protection of the eight lanthanide cations bound in the dendrimer structure and the high absorptivity leads to the red emission from Eu3+ that is easily observed in solution under irradiation with 354 nm UV light.     

Thermal decomposition of metal complexes. IX. Polynuclear complexes of lanthanide(III) ions with a metal schiff base complex as ligand

The kinetics of the thermal decomposition of some binuclear and trinuclear complexes of lanthanide(III) ions with the ligand N, N′-propilenbis (salicylideniminato) Cu(II) were studied under high vacuum (2 × 10⁻⁶ mm Hg) and in isothermal conditions. The trend of E^*_a values of the heavier lanthanoid complexes does not fit a reliable relation with the ionic radius, while the lighter lanthanoid complexes parallel those observed in other already studied lanthanoid derivatives.     

X-ray crystal structure of phenylglycine hydrazide: synthesis and spectroscopic studies of its transition metal complexes

Phenylglycine hydrazide was synthesized and investigated by X-ray crystallography. It crystallizes in the monoclinic space group P121/c with cell parameters a=5.9459 (18) Angstrom, b=5.1940 (16) Angstrom, c=26.7793 (83) Angstrom and Z=2. Its conformational changes, on complexation with transition metal ions Cu(II), Co(II), Ni(II), Mn(II) and Zn(II) has been studied on the basis of elemental analysis, magnetic moment and spectral (IR, (1)H NMR, UV-vis) studies. The bidentate nature of the ligand was confirmed on the basis of a comparative IR and NMR spectral studies. The trigonal bipyramidal geometries were observed for Cu(II), Ni(II) and Co(II) complexes, while it is octahedral for the remaining complexes. The conductivity data suggest them to be non-electrolytes.     

First mixed hydrazide/hydroxylamide metal aggregates

The first organometallic clusters of mixed hydrazide/hydroxylamide clusters of zinc, [Zn(MeZn)(4)(HNNMe(2))(2)(ONEt(2))(4)] and {Zn(EtZn)(4)[HNN(CH(2))(5)](2)(ONEt(2))(4)} were synthesized in one-pot synthesis protocols from dialkylzinc solutions, substituted hydrazines and N,N-diethylhydroxylamine; competing for the Zn atoms, the different binding properties of hydrazide and hydroxylamide ligands in these heteroleptic clusters are discussed.     

Solid state decomposition studies on metal salicylates. Thermal decomposition of some lanthanide salicylato complexes

The thermal stability and mechanism of thermal decomposition in air of the four lanthanide complexes of 2-hydroxybenzoic acid have been studied by TG, DSC, IR and MS techniques. An analysis of the prepared compounds show that Pr(III), Nd(III) and Tb(III) form anhydrous salicylato (Hsal)⁻ complexes while the corresponding holmium compound contains four water molecules. The TG curves show two (praseodymium, terbium), three (neodymium) or four (holmium) main stages of thermal decomposition. The most unstable among the complexes studied is Ho(Hsal)₃·4H₂O which releases four water molecules in an endothermic dehydration step. Ligand molecules decompose mainly in two stages of which the first is endothermic and is attributed to the release of the ligand acid and the second is a strongly exothermic decarboxylation process. The final decomposition product is the corresponding lanthanide(III) oxide, except in the case of terbium which decomposes to Tb₄O₇.     

Solution structure of chiral lanthanide complexes

The determination of solution structure of small to medium size chiral lanthanide complexes through paramagnetic NMR and circular dichroism is briefly reviewed. The main focus is on ytterbium as the rare earth, because of its negligible contact contribution to the hyperfine shift and of its intense CD spectrum in the near IR. The structures discussed contain various stereogenic elements: classical chiral centres, atropisomeric axes, slowly interconverting conformations, which gives rise to a manifold of situations to be identified, classified, and characterised through spectroscopic tools. The fallout of these structural properties are in enantioselective catalysis, in molecular recognition, or even in biomedicine, on account of the role of Gd³⁺ complexes as MRI contrast agents. Moreover, the information encoded in the NMR and CD spectra of Ln³⁺ complexes may be used to extract original data on the solution stereochemistry of organic molecules used as ligands. The first part summarises some basic theoretical aspects, with special emphasis onto those which have practical consequences in the experimental design. A discussion of selected applications can be found in the second part.     

Heterometallic lanthanide group 12 metal iodides

Neodymium tri-iodide reacts with Group 12 metal (M; M = Zn, Cd, Hg) iodides to form heterometallic compounds. These Lewis acidic M cleave Nd-I bonds to give either ionic ([(THF)(5)NdI(2)][MI(3)THF]; M = Zn, Cd) or charge-neutral [(THF)(5)NdI(micro(2)I)HgI(3)] compounds. Differences in structure are interpreted primarily in terms of M-L bond strengths, rather than Nd-L bond strengths. Experiments with Yb indicate that if there is any excess iodide present in these syntheses then the most readily isolated product is a triiodide salt, i.e., [(THF)(5)YbI(2)][I(3)]. In conventional solvents the presence of Lewis acid is not required for iodide displacement-from pyridine, "YbI(3)" crystallizes as [(py)(5)YbI(2)][I]. These compounds are potentially useful as heterometallic sources of lanthanide-doped iodide matrixes, they illustrate the ease with which iodides are displaced from lanthanide coordination spheres, and they underscore the complexity associated with using lanthanide iodides as Lewis acid catalysts.     

Expeditious synthesis of ‘P’-protected macrocycles en route to lanthanide chelate metal complexes

Phosphonic acid appended tetraazacyclododecane (cyclen)-based macrocycles are attractive metal-ion chelators for diagnostic imaging and therapeutic delivery. Here, we report a novel P-protected methodology that facilitates the rapid synthesis and purification of targeted phosphonic acid bearing macrocycles. Purification of these intermediates is facile, and deprotection using neat TFA is rapid, yet mild enough to preserve the integrity of delicate peptides and/or targeting moieties.