Crystal structures of three anionic lanthanide–aluminium [3.3.1] metallacryptate complexes

The three isomorphous [3.3.1] metallacryptate complexes bis(pyridinium) diaquadipyridinehexakis[μ3-salicylhydroximato(3−)]bis[μ2-salicylhydroximato(1−)]hexaaluminiumgadolinium–pyridine–water (1/7.396/1), (C5H6N)2[GdAl6(C7H6NO3)2(C7H4NO3)7(C5H5N)1.855(H2O)2]·7.396C5H5N·H2O or [Hpy]2[GdAl6(H2shi)2(shi)7(py)1.855(H2O)2]·7.396py·H2O, 1, bis(pyridinium) diaquadipyridinehexakis[μ3-salicylhydroximato(3−)]bis[μ2-salicylhydroximato(1−)]hexaaluminiumdysprosium–pyridine–water (1/7.429/1), (C5H6N)2[DyAl6(C7H6NO3)2(C7H4NO3)7(C5H5N)1.855(H2O)2]·7.429C5H5N·H2O or [Hpy]2[DyAl6(H2shi)2(shi)7(py)1.891(H2O)2]·7.429py·H2O, 2, and bis(pyridinium) diaquadipyridinehexakis[μ3-salicylhydroximato(3−)]bis[μ2-salicylhydroximato(1−)]hexaaluminiumytterbium–pyridine–water (1/7.386/1), (C5H6N)2[YbAl6(C7H6NO3)2(C7H4NO3)7(C5H5N)1.855(H2O)2]·7.429C5H5N·H2O or [Hpy]2[YbAl6(H2shi)2(shi)7(py)1.818(H2O)2]·7.386py·H2O, 3, where Hpy+ is pyridinium, shi3− is salicylhydroximate, and py is pyridine, consist of an aluminium-based metallacryptand that captures an Ln III ion in the central cavity. The metallacryptand portions are comprised of an Al—N—O repeat unit; thus, they can be considered three-dimensional metallacrowns. The encapsulated Ln III ions are nine-coordinate with a spherical capped-square-antiprism geometry, while the six AlIII ions are all octahedral. Four of the AlIII ions are chiral centers with 2 Δ and 2 Λ stereoconfigurations. The remaining two AlIII ions have trans chelate rings from two different shi3− ligands. For 1–3, a section of the main molecule is disordered induced by the presence or absence of a pyridine ligand coordinated to one of the AlIII ions. In the absence of the pyridine moiety, an H2shi− ligand moves into the space otherwise occupied by the pyridine and the phenol oxygen atom coordinates to the AlIII ion. The movement of the H2shi− ligand induces movement for the Ln III ion, for another AlIII ion that also binds the same H2shi− ligand, and for one of the shi3− ligands coordinated to the latter AlIII ion. For 1–3 the occupancy ratio of the metallacryptand portions refined to 0.8550 (13):0.1450 (13), to 0.8909 (13):0.1091 (13), and to 0.8181 (14):0.1819 (14), respectively.

Regulating the single-molecule magnetic properties of phenol oxygen-bridged binuclear lanthanide complexes through the electronic and spatial effect of the substituents

Series of Dy2 SMMs displayed the nearly maximum tenfold increase in energy barrier and the hysteresis temperature increased from zero to 2.5 K using the electronic and spatial effect on substituent of the bridging ligand and co-ligands.

Synthesis of 3-(2-Hydroxyphenyl)-5-(2-Pyridinyl)-1,2,4-triazoles as a potential chelate ligand for Uranyl ion

Two new uranyl complexes with the molecular formula [(UO2)(H2L1)](СH3OH) and [(UO2)(H3L2)](СH3OH) {H4L1 = 2-[5-[[5-[[5-(2-pyridyl)-1H-1,2,4-triazol-3‑yl]methyl]-1H-1,2,4-triazol-3-yl]methyl]-1H-1,2,4-triazol-3-yl]phenol and H5L2 = 2-[5-[[5-[[5-[[5-(2-pyridyl)-1H-1,2,4‑triazol-3-yl]methyl]-1H-1,2,4-triazol-3-yl]methyl]-1H-1,2,4-triazol-3-yl]methyl]-1H-1,2,4-triazol-3-yl]phenol)} have been synthesized. All compounds have been characterized by NMR and IR spectroscopy. With H4L1 and H5L2 uranyl ion forms mononuclear complexes. In [(UO2)(H3L2)](СH3OH) pyridyl nitrogen was uncoordinated and bonding of H5L2 was realized only through phenol oxygen and N4-nitrogens of triazole cycles.

Structural and Spectroscopic Properties of Two New Isostructural Complexes of Lapacholate with Cobalt and Copper

The molecular structures of two isostructural complexes of lapacholate (Lap) anion and dimethylformamide (DMF), M(Lap)2(DMF)2 with M: Co Cu, were determined by X-ray diffraction methods. The substances crystallize in the triclinic space group P1¯ with one molecule per unit cell and cell constants a=7.7591(3), b=10.3560(3), c=11.2224(4) Å, α=95.110(2), β=94.310(2), and γ=107.704(2)° for the Co complex and a=7.9308(2), b=10.0033(4), c=10.7508(4), α=97.387(2), β=93.621(2), and γ=103.980(2)° for the Cu complex. The structures were solved from 2933 (Co) and 2888 (Cu) reflections with I>2σ (I) and refined by full matrix least squares to agreement R1-factors of 0.041 (Co) and 0.033 (Cu). The metal M(II) ion is sited on a crystallographic inversion center in a MO6 distorted octahedral environment. This ion is coordinated equatorially to two lapacholate anions through their adjacent carbonyl and phenol oxygen atoms [M–O bond distances of 2.134(1) and 2.008(1) Å (Co) and 2.301(1) and 1.914(1) Å (Cu)] and axially to two DMF molecules through oxygen atoms [M–O bond lengths of 2.143(1) Å (Co) and 2.069(1) Å (Cu)]. The solid state IR transmittance and solution electronic absorption spectra of both Co and Cu compounds are also reported and compared to each other and to the corresponding spectra of other members of the lapacholate metal family of complexes.

pH-Potentiometric Investigation towards Chelating Tendencies ofp-Hydroquinone and Phenol Iminodiacetate Copper(II) Complexes

Copper ions in the active sites of several proteins/enzymes interact with phenols and quinones, and this interaction is associated to the reactivity of the enzymes. In this study the speciation of theCu2+with iminodiacetic phenolate/hydroquinonate ligands has been examined by pH-potentiometry. The results reveal that the iminodiacetic phenol ligand forms mononuclear complexes withCu2+at acidic and alkaline pHs, and a binuclearOphenolate-bridged complex at pH range from 7 to 8.5. The binucleating hydroquinone ligand forms only 2 : 1 metal to ligand complexes in solution. The pK values of the protonation of the phenolate oxygen of the two ligands are reduced about 2 units after complexation with the metal ion and are close to the pK values for the copper-interacting tyrosine phenol oxygen in copper enzymes.

2-Hydroxyisophthalic acid: hydrogen-bonding patterns in the monohydrate and the tetraphenylphosphonium salt. An instance of dramatic acidity enhancement by symmetric, internally hydrogen-bonded anion stabilization

The monohydrate of the title phenolic diacid (C8H6O5·H2O, 2-hydroxybenzene-1,3-dioic acid or 3-carboxysalicylic acid) adopts a planar conformation, with the phenol hydrogen internally hydrogen-bonded to the carbonyl of one highly ordered carboxyl, which, in turn, donates a hydrogen bond to the oxygen of water. The second carboxyl is disordered and hydrogen-bonded both to water and to the disordered carboxyl of a centrosymmetrically related neighbor in a static disorder arrangement extending over two full asymmetric units. The water accepts either one or two hydrogen bonds and donates a long bifurcated hydrogen bond shared equally by O atoms of the phenol and the disordered carboxyl. The hydrogen bonding includes no standard carboxyl pairing and is entirely two-dimensional. The resulting planar ribbons stack translationally at a distance of 3.413 (8) Å, in an offset arrangement having non-translational interplanar distances of 0.821 (5) and 2.592 (6) Å. This structure is compared with two previously reported for this compound. The title compound forms a monoanion, whose tetraphenylphosphonium salt is described (C32H25O5P, tetraphenylphosphonium 2,6-dicarboxyphenolate, tetraphenylphosphonium 2-oxidoisophthalic acid or tetraphenylphosphonium 3-carboxysalicylate). The phenol oxygen is the site of formal negative charge on the anion, which is stabilized in a planar arrangement by symmetrical hydrogen bonds from both ortho-carboxyl groups. The energetics of this arrangement, the phenol and carboxyl acidities, and factors affecting those acidities and providing anion stabilization are discussed.

Transition metal complexes with thiosemicarbazide-based ligands, part 46: Synthesis and physico-chemical characterization of mixed ligand cobalt(III)-complexes with salicylaldehyde semi-, thiosemi- an

Mixed ligand octahedral cobalt(III) complexes with the tridentate salicylaldehyde semi-, thiosemi- and isothiosemicarbazone and pyridine of general formula [CoIII(L1-3)(py)3]X(H2L1=salicylaldehyde semicarbazone X=[CIICl3(py)]-, ClO4-.H2O, I-. 0.5 I2; H2L2=salicylaldehyde thiosemicarbazone, X=[CoIICl3(py)]-, CoIIBr3(py)]-, ClO4-. H2O, I3-; H2L3 = salicylaldehyde S-methylisothiosemicarbazone, X=[CoIIBr3(py)]-, ClO4-. H2O, BF4-) were synthesized. The tridentate coordination of all the three dianionic forms of the ligands involves the phenol oxygen, hydrazine nitrogen and the chalcogen (O or S) in case of salicylaldehyde semi thiosemicarbazone and the terminal nitrogen atom in the case of isothiosemicarbazone. For all the complexes, a meridial octahedral arrangement is proposed, which is a consequence of the planarity of the chelate ligand. The compounds were characterized by elemental analysis molar conductivity, magnetic susceptibility, IR and electronic absorption spectra. The thermal decomposition of the complexes was investigated by thermogravimetry, coupled TG-MS measurements and DSC.