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New ytterbium (III) compounds with β-diketones (2,7-dimethyl-octene-1-dione-3,5 and 2,6-dimethylheptene-1-dione-3,5) and their derivatives with phenanthroline have been synthesized. The composition and chemical structure of the obtained complexes have been determined by several Phy­sico-chemical investigations. It has been shown, that the Yb (III) ion coordinates three ligand molecules and the coordination sphere of the complexes is supplemented by two mole­cules of water or a molecule of phenanthroline. It has been shown that the СN of the ytterbium ion is 8, the coordination polyhedron is a square antiprism, and the complex is characte­rized by no cubic symmetry. All synthesized compounds exhibit intense IR luminescence. The significant increase in the relative emission intensity of mixed ligand complexes is due to the additional antenna effect of the phenanthroline molecule.

Three nickel(II), manganese(II) and cadmium(II) complexes, [NiL2] (I), [MnL2] (II) and [Cd(HL)2(NO3)]·NO3 (III), derived from 4-bromo-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide (HL) were prepared and characterized by IR and UV spectra. Structures of the complexes were further confirmed by single crystal X-ray diffraction techniques (CIF files CCDC nos. 1874307 (I), 1874308 (II), and 1874309 (III)). The Ni atom in complex I and the Mn atom in complex II are in octahedral coordination. The Cd atom in complex III is in square antiprism coordination. The nickel complex is effective on the inhibition of Jack bean urease.

The mononuclear complexes [Dy(3Br,5Cl-H3L1,1,4)(D)]·solvate (D = H2O, solvate = 0.25MeOH, 1W·0.25MeOH; D = Py without solvate, 1Py), and [Dy(3NO2,5Br-H3L1,1,4)(H2O)] (2W) were isolated. The crystal structures of 1W·0.25MeOH, 1Py and 2W·2CH3C6H5 show that the DyIII ion is octacoordinated, in N4O4 or N5O3 environments, with distorted geometries, between square antiprism, biaugmented trigonal prism and triangular dodecahedral. A similar environment for the metal ion is shown in the chiral crystals of the diamagnetic yttrium analogue [Y(3Br,5Cl-H3L1,1,4)(MeOH)] (3M), which were spontaneously resolved. Magnetic analyses of the three dysprosium complexes, and their diluted analogous 1W@Y, 1Py@Y and 2W@Y, reveal that none of them seem to relax through an Orbach mechanism at Hdc = 0. However, the three complexes show Orbach relaxation under Hdc = 1000 Oe, and 1Py is the in-field SIM with the highest energy barrier among these complexes, with a Ueff value of 358 K. Analysis of ac magnetic data shows that the electron-withdrawing substituents on the phenol rings of the aminophenol ligands, as well as the auxiliary oxygen donors from water ligands, reduce the energy barriers of the complexes, which is attributed to a charge reduction in the coordinating atoms of the aminophenol donor. Ab initio calculations support the experimental results.

Based on the organic ligand 2,2′-(((pyridine-2,6-diylbis(methylene))bis((pyridin-2-ylmethyl)-azanediyl))-bis(methylene))diphenol (H2L), and dysprosium salts with different anions, two mononuclear and one dinuclear complexes, namely, [Dy(L)(H2O)](ClO4)·2CH3CH2OH (1), [Dy(L)(NO3)] (2) and [Dy2(L)(dbm)4] (3, Hdbm = dibenzoylmethane), were synthesized and structurally and magnetically characterized. In complexes 1 and 3, the Dy centers are octa-coordinated with triangular dodecahedral (local D2d symmetry) environments. Complex 1 is dimeric by hydrogen bond interactions between coordinated water molecules. In complex 3, two DyIII ions are linked by two phenoxy oxygen atoms to form a dinuclear cluster. The DyIII ion in complex 2 is nine-coordinated and adopts a spherical capped square antiprism geometry with a C4v symmetry. Magnetic measurements and theoretical calculations reveal that the magnetic couplings between two phenoxyl-bridging DyIII ions in complex 3 are antiferromagnetic and mostly originate from the exchange coupling. Both complexes 1 and 2 exhibit single molecule magnet behaviors under zero direct-current field with effective energy barriers of 50.94 K and 12.26 K, respectively. Complex 3 only exhibits frequency-/temperature-dependent out-of-phase signals, and no peak is observed.

A triangular prismatic metal-organic cage based on mixed valence copper ions has been designed and synthesized by using metallocycle panels and pillar ligands. The triangular prism will be quickly transformed to a 10-nuclear cage upon an external chemical stimulus, which features a bicapped square antiprism structure. This prismatic cage can act as a catalyst for oxidation of aromatic alcohols to their corresponding aromatic aldehydes with high yields at room temperature under O2 atmosphere.

The study reveals the relationship between structural and spectroscopic characteristics of lanthanide dipivaloylmethanates with 2,2′-bipyridine derivatives [Ln(DPM)3L] (Ln = Eu, Tb; L = 2,2′-bipyridine, 4,4′-dimethyl-2,2′-bipyridine, 4,4′-diphenyl-2,2′-bipyridine) and fluorinated β-diketonates [Ln(β)3Bpy] (β = TTFA, TFAA, BTFA) with the CN (Ln3+) = 8 and the LnN2O6 coordination polyhedron in the form of a square antiprism. We discuss structural regularities resulting from the difference between Eu–O and Eu–N bond lengths in β-diketonates due to the changes in donor-acceptor properties of substituents and the steric factor. The effect of the main distortion Δ = r(Eu–N) – r(Eu–O) of the Eu coordination polyhedron on the luminescence spectra and vibrational Raman spectra is considered. A qualitative correlation is demonstrated between the relative intensity of the 5D0–7F2 (Eu3+) electric dipole transition, which characterizes the degree of distortion of the nearest environment of the Eu3+ ion, and the lifetimes of excited electronic states 5D0 (Eu3+) and 5D4 (Tb3+). The contribution of nonradiative processes caused by high-frequency vibrations of ligands to the decay rate of 5D0 (Eu3+) and 5D4 (Tb3+) levels is discussed. The Raman spectra are analyzed in terms of studying the changes in vibrational frequencies of the Bpy molecule depending on the distortion Δ of the Eu coordination polyhedron.

Three new main group ferrocenyldithiocarbamate complexes, viz., {Pb[(FcCH2)(CH2CH2OH)(NCS2)]2}·(FcCH2-3-oxazolidine-2-thione)·(H2O) (1), {Sb[(FcCH2)(CH2CH2OH)(NCS2)]3} (2) and {Bi[(FcCH2)(CH2CH2OH)(NCS2)]3} (3), (Fc = ferrocenyl) have been synthesized and characterized by elemental analyses and IR, 1H and 13C NMR spectroscopy as well as X-ray crystallography. The X-ray analysis of 1 indicates distorted trigonal bipyramidal geometry around Pb(II) and a cyclised product, 3-ferrocenylmethyl-oxazolidine-2-thione (4), co-crystallizes with 1. The geometry around Sb(III) in 2 is pseudo-octahedral, while 3 forms a dimer, displaying distorted square antiprism geometry around the Bi(III) center. Several attempts to synthesize the pure cyclised product 3-ferrocenylmethyl-oxazolidine-2-thione (4) using Pb(II) salts failed but 4 was fortuitously obtained in an attempt to synthesize the Cu(I) cluster by the comproportionation of {Cu[(FcCH2)(CH2CH2OH)(NCS2)]2} using copper powder. Interestingly, varying the reaction time yielded another completely desulfurized cyclised product 3-ferrocenylmethyl-oxazolidine-2-one (5). Both 4 and 5 have been characterized using spectroscopic techniques and X-ray crystallography, and the possible mechanism for the conversion of {Cu[(FcCH2)(CH2CH2OH)(NCS2)]2} to 3-ferrocenylmethyl-oxazolidine-2-thione (4) has been explained with the help of periodic UV-Vis and ESI-MS experiments. This investigation will pave a new pathway for the synthesis of similar cyclised products using similar safe and sustainable reaction conditions.

By employing mixed ligands, a new trinuclear dysprosium complex [Dy3(dbm)3(L)4](ClO4)2·CH2Cl2·2MeOH (1, Hdbm = dibenzoylmethane; HL = 2-methoxy-6-((quinolin-8-ylimino)methyl)phenol) was synthesized by a one-pot reaction. According to structural characterization, all the 8-coordinated Dy(iii) sites are well arranged with slightly distorted square antiprism (D4d) geometries. Magnetic measurements reveal that 1 exhibits typical single-molecule magnetic behavior at zero magnetic field and shows rarely open hysteresis loops up to 3 K among open-ring {Dy3} SMMs, where the relaxation time remains very stable under the protection from the Dy-Dy magnetic coupling in the open-ring arrangement of Ising spins.

Here, we report our trials to regulate the luminescence performance of the macrocyclic samarium(III) complex and prepare four excellent luminescent Sm(III) complex-doped poly(methylmethacrylate) (PMMA) composites. Four 23-membered [1 + 1] Schiff-base macrocyclic mononuclear Sm(III) complexes, Sm-2a–Sm-2d, originating from dialdehydes with different pendant arms and 1,2-bis(2-aminoethoxy)ethane, have been constructed by the template method. Crystal structures reveal that every Sm(III) ion with the coordination geometry of a distorted bicapped square antiprism is capsulated by the macrocyclic cavity environment forming the “lasso-type” protection. Relative photophysical properties of macrocyclic Sm(III) complexes are carefully investigated in solid-state, methanol solution, and doped PMMA film, and all these show characteristic emissions of the Sm(III) ion associated with satisfactory lifetimes and quantum yields in all media, which could be comparable to reported outstanding examples. Especially, the luminescence performance for this type of Sm(III) complex could be regulated in the solid state by the use of different functional groups in the pendant arm while it is not achieved in solution and the doped PMMA composite. High emitting and air-stable plastic materials could be obtained when these Sm(III) complexes are doped in PMMA with 0.1 wt % mixing ratio, and the corresponding maximum lifetime and quantum yield are 61.2 μs and 0.63% in the case of complex Sm-2a, respectively. We believe that these highly luminescent “lasso-type” Sm(III) complexes and doped PMMA composites are valuable references in the design of luminescent lanthanide(III) hybrid materials.

The first complexes of cerium tetrafluoride in solutions have been studied by 19F NMR and IR spectroscopy. The temperature dependence of the 19F NMR spectra has been explored, and conclusion has been made that dynamic equilibrium between the molecular adduct and singly charged ionic forms, including geometric isomers, exists in solution. The statistical probability for the formation of [CeF4(dmso)4] stereoisomers of square antiprism configuration has been calculated, and their assignment to possible stereoisomers have been made on the basis of relative intensities of the 19F NMR signals. Quantum-chemical calculations of the structure of one of the possible isomers have been performed for the [CeF4(dmso)4] molecular adduct, [CeF3(dmso)5]+ cation, and [CeF5(dmso)3]– anion to show their thermodynamic stability.

Lanthanide pyrrole-2-carboxylates [{Ln(L)3(H2O)2}·H2O]n (Ln = Eu, Gd, Tb) were synthesized and investigated using single crystal X-ray diffraction and optical spectroscopy (luminescence, luminescence excitation and vibrational IR spectra). The europium pyrrole-2-carboxylate crystallizes as a 2D network structure in the P21/c space group. The Eu3+ coordination polyhedron formed by five carboxylic groups and two water molecules can be described as a distorted single-capped square antiprism. The luminescence spectra indicate a low symmetry of the charge distribution around the Ln3+ ion that corresponds to the C1 symmetry of the coordination environment of Eu3+ ion in the [{Eu(L)3(H2O)2}·H2O]n crystal lattice. The low-energy ligand–metal charge transfer (LMCT) state was identified in the europium compound. The shortening of the 5D0 (Eu3+) lifetime in the 230–295 K temperature region, when the compound is heated from 77 to 295 K, and the low luminescence intensity of the europium pyrrole-2-carboxylate are caused by the participation of the LMCT state in quenching processes. The energy of activation determined for the 5D0 – LMCT crossover is 3900 ± 100 cm−1.

We report the crystal structure of Ba(CN3H4)2 as synthesized from liquid ammonia. Structure solution based on X-ray diffraction data suffers from a severe pseudo-tetragonal problem due to extreme scattering contrast, so the true monoclinic symmetry is detectable only from neutron powder diffraction patterns, and structure solution and refinement was greatly aided by density-functional theory. The symmetry lowering is due to slight deviations of the guanidinate anion from the mirror plane in space group P 4 ‾ b2, a necessity of hydrogen bonding. At 300 K, barium guanidinate crystallizes in P21/c with a=6.26439(2) A, b=16.58527(5) A, c=6.25960(2) A, and a monoclinic angle of β=90.000(1)°. To improve the data-to-parameter ratio, anisotropic displacement parameters from first-principles theory were incorporated in the neutron refinement. Given the correct structural model, the positional parameters of the heavy atoms were also refinable from X-ray diffraction of a twinned crystal. The two independent guanidinate anions adopt the all-trans- and the anti-shape. The Ba cation is coordinated by eight imino nitrogens in a square antiprism with Ba-N contacts between 2.81 and 3.04 A. The IR and Raman spectra of barium guanidinate were compared with DFT-calculated phonon spectra to identify the vibrational modes.

Four new coordination polymers based on the use of the [Cr(pyim)(C2O4)2]− species as a metalloligand, namely [LiCr(pyim)(C2O4)2(MeOH)]n (1), {[CaCr2(pyim)2(C2O4)4]·2MeOH}n (2), {[SrCr2(pyim)2(C2O4)4(H2O)]·0.45MeOH·4.55H2O}n (3) and {[CdCr2(pyim)2(C2O4)4]·MeOH}n (4) [pyim = 2-(2′-pyridyl)imidazole] have been synthesized and characterized by elemental analyses, IR spectra and X-ray diffraction on single crystals. Complex 1 is a neutral heterobimetallic chain where the tris(chelated) chromium(III) unit acts as a bis-bidentate ligand towards {Li(MeOH)}+ fragments through its two oxalate ligands, each lithium ion being five-coordinate in a intermediate surrounding between square pyramidal and trigonal bipyramidal. The structure of 2 consists of neutral oxalato-bridged chromium(III)-calcium(II) double chains of single chirality [all the tris(chelated) chromium centres have the same chirality either Λ or λ] and methanol molecules of crystallization. Each calcium ion in 2 exhibits a square antiprism environment which is built by four bidentate oxalate ligands from four [Cr(pyim)(C2O4)2]− units. Neutral oxalato-bridged chromium(III)-strontium(II) double chains also occur in 3 with methanol and water molecules of crystallization, each alkaline-earth cation being nine-coordinate in a monocapped square antiprism environment which is defined by a water molecule and eight oxalate-oxygens from four [Cr(pyim)(C2O4)2]− units. The CrIII2MII2 loops [M = Ca (2) and Sr (3)] within each double chain are planar. The structure of 4 is also made of neutral oxalato-bridged chromium(III)-cadmium(II) double chains but in contrast to 2 and 3, the chirality of the tris(chelated) chromium unit in 4 is alternated in each loop and the adjacent CrIII2CdII2 loops are not planar but form a dihedral angle of 84.8°. The potential use of the [Cr(pyim)(C2O4)2]− entity as a metalloligand in designing heterobimetallic compounds is analyzed and discussed.

Herein we report a stable and high-performance Dy(iii) single-ion magnet (SIM) showing an energy barrier of 944 K under zero dc field, with an open hysteresis loop up to 6 K. To the best of our knowledge, this is the highest energy barrier for a square antiprism as well as phosphine oxide based Dy-SIMs, reported so far.

In this paper we report a novel probe based on a luminescent 23-membered [1 + 1] Schiff-base macrocyclic mononuclear Sm(iii) complex Sm-2e, originating from the dialdehyde H2Qe and 1,2-bis(2-aminoethoxy)ethane precursors, which is synthesized by the Sm(iii) ion template method. X-ray structural analyses confirm that each ten-coordinate Sm(iii) center with the coordination geometry of a distorted bicapped square antiprism is fully encapsulated by a flexible macrocyclic ligand H2L2e to form a "lasso-type" architecture, and this architecture could enable efficient energy transfer in various solvents confirmed by long lifetimes (33.5-65.2 μs) and high quantum yields (0.23-0.76%) of the Sm(iii) ion. Simultaneously, complex Sm-2e could serve as a probe for sensing organic solvents. Particularly, this complex probe Sm-2e exhibits a highly selective, rapid and sensitive response to tetrahydrofuran (THF), which is easily distinguished by a large absorption shift, even visible to the naked eye, and complete fluorescence quenching. Moreover, the limit of detection for THF is about 0.20% determined by titration experiments, and good selectivity for THF could still be realized in mixture solvents. Consequently, this colorimetric and "turn off" fluorescent probe Sm-2e could be a valuable candidate as a sensor material for sensing THF which has been rarely reported.

A series of binuclear dysprosium compounds, namely, [Dy(api)]2 (1), [Dy(api)]2·2CH2Cl2 (2), [Dy(Clapi)]2·2C4H8O (3), and [Dy(Clapi)]2·2C3H6O (4) (H3api = 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazoline; H3Clapi = 2-(2′-hydroxy-5′-chlorophenyl)-1,3-bis[3′-aza-4′-(2′′-hydroxy-5′′-chlorophenyl)prop-4′-en-1′-yl]-1,3-imidazolidine), have been isolated by the reactions of salen-type ligands H3api/H3Clapi with DyCl3·6H2O in different solvent systems. Structural analysis reveals that each salen-type ligand provides a heptadentate coordination pocket (N4O3) to encapsulate a DyIII ion and all of the DyIII centers in 1–4 adopt a distorted square antiprism geometry with D4d symmetry. Magnetic studies showed that compound 1 did not exhibit single-molecule magnetic (SMMs) behavior. With the introduction of different lattice solvents, compounds 2–4 showed filed-induced slow magnetic relaxation with barriers Ueff of 18.2 K (2), 28.0 K (3) and 16.4 K (4), respectively. Ab initio calculations were employed to interpret the magnetization behavior of 1–4. The combination of experimental and theoretical data reveal the importance of the weak exchange interaction between the DyIII ions in the observation of slow magnetic relaxation, and a relaxation mechanism has been developed to rationalize the observed difference in the Ueff values. The different lattice solvents influence Dy–O–Dy bond angles and thus alter the torsion of the square antiprism geometry, consequently resulting in distinct magnetic interactions and the magnetic behavior.

A thorough structural characterization of the La(NO3)3 salt dissolved into several mixtures of ethyl ammonium nitrate (EAN) and methanol (MeOH) with EAN molar fraction χEAN ranging from 0 to 1 has been carried out by combining molecular dynamics (MD) and X-ray absorption spectroscopy (XAS). The XAS and MD results show that changes take place in the La3+ first solvation shell when moving from pure MeOH to pure EAN. With increasing the ionic liquid content of the mixture, the La3+ first-shell complex progressively loses MeOH molecules to accommodate more and more nitrate anions. Except in pure EAN, the La3+ ion is always able to coordinate both MeOH and nitrate anions, with a ratio between the two ligands that changes continuously in the entire concentration range. When moving from pure MeOH to pure EAN, the La3+ first solvation shell passes from a 10-fold bicapped square antiprism geometry where all the nitrate anions act only as monodentate ligands to a 12-coordinated icosahedral structure in pure EAN where the nitrate anions bind the La3+ cation both in mono- and bidentate modes. The La3+ solvation structure formed in the MeOH/EAN mixtures shows a great adaptability to changes in the composition, allowing the system to reach the ideal compromise among all of the different interactions that take place into it., The structural properties of the La(NO3)3 salt dissolved into EAN/methanol mixtures were characterized by molecular dynamics and X-ray absorption spectroscopy. The La3+ solvation shell undergoes significant changes with increasing the ionic liquid content of the mixture, progressively losing methanol molecules to accommodate more and more nitrate anions. The La3+ solvation structure shows great adaptability to composition changes, passing from a 10-fold bicapped square antiprism geometry in pure methanol to a 12-coordinated icosahedral complex in EAN.

Accurate knowledge of rare earth elements (REE) speciation in high pressure – high temperature fluids is required to model REE transport and precipitation in subduction zones and magmatic-hydrothermal environments, and the formation of rare metal deposits. Recent experiments (lanthanum, ytterbium, erbium) have demonstrated that REE chloride complexes are the main REE form in many hydrothermal fluids (Migdisov et al., 2016). However, the speciation of yttrium (Y(III)), a cation with an ionic radius similar to that of Ho(III), remains poorly constrained in chloride-rich hydrothermal solutions. We used ab initio molecular dynamics (MD) simulations to calculate the nature of Y(III)-Cl complexes and the thermodynamic properties of these species at temperatures up to 500 °C and pressures of 800 bar and 1000 bar. The MD results were complemented by in situ X-ray absorption spectroscopy (XAS) measurements. Our results indicate that at temperatures below 200 °C, chloro-complexes do not form readily, even in highly concentrated brines. At ambient condition, the Y(III) aqua ion binds to eight water molecules in a square antiprism geometry, which is consistent with previous ab initio studies (Ikeda et al., 2005a). The thermodynamic integration method was employed to calculate the formation constants (log K Θ ) of Y(III)-Cl− complexes in two simulation boxes containing different Y:Cl ratios; we obtained very consistent results of the standard log K Θ of the individual complexes from the two independent calculations, which confirms that the thermodynamic integration method is reliable and not significantly affected by technical limitations in box size, box composition, or simulation time. Based on the derived formation constants, we fit modified Ryzhenko–Bryzgalin (MRB) equation of state parameters, which enable extrapolation of the formation constants at elevated temperature and pressure. The results are consistent with the XAS data, and show that the stability of Y(III)-Cl complexes increases with increasing temperature, Y(III) forming high order Cl− complexes (up to YCl4−) in high salinity solutions at high temperature and pH = 3. We also compare the extrapolated log K Θ with the available data for other REE at 150 °C, 200 °C and 250 °C. At 200 °C, yttrium behaves more like a heavy REE, but from 200 °C to 250 °C, the formation constants of Y(III)-Cl complexes increase dramatically and behave more like the light REE. The difference of Cl− dominant species between Ho(III) (HoCl2+) and Y(III) (YCl2+) may account for the formation of anomalous Y/Ho ratios in some hydrothermal environments.

Two one-dimensional dysprosium(III) complexes based on α-glycine (gly) and β-alanine (β-ala) amino acids, with the formula {[Dy2(gly)6(H2O)4](ClO4)6·5H2O}n (1) and {[Dy2(β-ala)6(H2O)4](ClO4)6·H2O}n (2), have been synthesised and characterised structurally and magnetically. Both compounds crystallise in the triclinic system with the space group P. In 1, two DyIII ions are eight-coordinate and bound to six oxygen atoms from six gly ligands and two oxygen atoms from two water molecules, showing different geometries (bicapped trigonal prism and square antiprism). In 2, two DyIII ions are nine-coordinate and bound to seven oxygen atoms from six β-ala ligands and two oxygen atoms from two water molecules in the same geometry (capped square antiprism). In the crystal packing of both compounds, cationic {[Dy2(L)6(H2O)4]6+}n [L = α-glycine (1) and β-alanine (2)] chains, ClO4− anions, and water molecules generate a network connected through H-bonding interactions. The study of the magnetic properties of 1 and 2 through dc magnetic susceptibility measurements reveals different magnetic behaviour 1 and 2. In addition, ac magnetic susceptibility measurements show a field-induced slow relaxation of magnetisation for both compounds, pointing out that the single-molecule magnet (SMM) phenomenon occurs in both 1 and 2.

The reactivity of the well-known pentadentate N3O2 Schiff base H2L (2,6-bis(2-hydroxyphenyliminomethyl)pyridine) towards a lanthanoid metal, in this case DyIII, has been investigated for the first time. This reactivity markedly depends on the pH of the medium and, accordingly, two different complexes, [Dy(HL)(NO3)2]·H2O (1·H2O) and [Dy(L)(NO3)(EtOH)(H2O)]·2H2O (2·2H2O), could be isolated from dysprosium(III) nitrate and H2L. In addition, reaction of H2L with dysprosium(III) chloride in methanol yields [Dy(HL′)2][Dy(L)(Cl2)] (3), where H2L′ ((6-(2-hydroxyphenyliminomethyl)-2-methoxyhydroxymethyl)pyridine) is an N2O2 hemiacetal donor derived from the partial hydrolysis of the H2L ligand, and subsequent addition of the methanol solvent to the carbonyl group. This latter reaction has been firstly observed for a lanthanoid metal. Single crystal X-ray diffraction studies of 1·1.15Py·0.3CH3C6H5, 2·2H2O and 3 show that the Schiff base is acting as a nearly flat pentadentate donor in all the cases, this behaviour being independent of the deprotonation degree of the phenolic oxygen atoms, both mono- or bisdeprotonated. Complexes 1·1.15Py·0.3CH3C6H5 and 2·2H2O show DyN3O6 cores, with distorted geometries closer to spherical tricapped trigonal prism or spherical capped square antiprism for 1·1.15Py·0.3CH3C6H5 and 2·2H2O, respectively. In the case of 3, the [Dy(HL′)2]+ cation shows a dysprosium ion in an N4O4 triangular dodecahedron environment, while the [Dy(L)(Cl2)]− anion displays a DyN3O2Cl2 core with distorted pentagonal bipyramidal geometry. Moreover, attempts to dilute 1·H2O with yttrium yielded single crystals of (Et3NH)[Dy0.09Y0.91(L)(NO3)2] (4), where the Schiff base shows a similar pentadentate coordination mode. Dynamic magnetic studies of 1·H2O, 2·2H2O and 3 show that 2·2H2O and 3 present field-induced slow relaxation of the magnetisation, with Ueff barriers of 46.1(9) and 31.0(7) K for 2·2H2O and 3, respectively, while 1·H2O does not exhibit frequency-dependent peaks of the out of phase susceptibility, even in the presence of an external dc magnetic field. By contrast, the dilute sample 4 behaves as a SIM at zero dc field, with an energy barrier of ca. 49 K. Ab initio calculations using CASSCF methods including spin–orbit effects qualitatively support the obtained magnetic results, indicating that axiality is not the only factor that should be taken into account in order to increase effective energy barriers.

The reaction of [Ni6(CO)12]2– as a [NBu4]+ salt in CH2Cl2 with 0.8 equiv of PCl3 afforded [Ni14P2(CO)22]2–. In contrast, the reactions of [Ni6(CO)12]2– as a [NEt4]+ salt with 0.4–0.5 equiv of POCl3 afforded [Ni22–xP2(CO)29–x]4– (x = 0.84) or [Ni39P3(CO)44]6– by using CH3CN and thf as a solvent, respectively. Moreover, by using 0.7–0.9 mol of POCl3 per mole of [NEt4]2[Ni6(CO)12] both in CH3CN and thf, [Ni23–xP2(CO)30–x]4– (x = 0.82) was obtained together with [Ni22P6(CO)30]2– as a side product. [Ni23–xP2(CO)30–x]4– (x = 0.82) and [Ni22P6(CO)30]2– were separated owing to their different solubility in organic solvents. All the new molecular nickel phosphide carbonyl nanoclusters were structurally characterized through single crystal X-ray diffraction (SC-XRD) as [NBu4]2[Ni14P2(CO)22] (two different polymorphs, P21/n and C2/c), [NEt4]4[Ni23–xP2(CO)30–x]·CH3COCH3·solv (x = 0.82), [NEt4]2[Ni22P6(CO)30]·2thf, [NEt4]4[Ni22–xP2(CO)29–x]·2CH3COCH3( x = 0.84) and [NEt4]6[Ni39P3(CO)44]·C6H14·solv. The metal cores’ sizes of these clusters range from 0.59 to 1.10 nm, and their overall dimensions including the CO ligands are 1.16–1.63 nm. In this respect, they are comparable to ultrasmall metal nanoparticles, molecular nanoclusters, or atomically precise metal nanoparticles. The environment of the P atoms within these molecular Ni–P–CO nanoclusters displays a rich diversity, that is, Ni5P pentagonal pyramid, Ni7P monocapped trigonal prism, Ni8P bicapped trigonal prism, Ni9P monocapped square antiprism, Ni10P sphenocorona, Ni10P bicapped square antiprism, and Ni12P icosahedron., Five new molecular nickel phosphide carbonyl clusters have been obtained displaying overall sizes in the range 1.16−1.63 nm and very diverse environments for the phosphide atoms.

A series of new anionic lanthanide(III) complexes with the general formula NEt4[LnL4] (1-Ln; HL = dimethyl[(4-methylphenyl)sulfonyl]amidophosphate; Ln = La, Nd, Eu), were synthesized and characterized by IR, UV–vis, and NMR spectroscopies, the differential scanning calorimetry method, thermogravimetric and X-ray analysis, and photoluminescence measurements. Single-crystal structures of NEt4[EuL4] (1-Eu) were determined at 293 and 100 K and evidenced the single-crystal-to-single-crystal phase transition. Both phases are in the monoclinic crystal system in centrosymmetric groups of the same Laue class. The room temperature structure is in C2/c (No. 15), while low-temperature structure is in the P21/c (No. 14) space groups. The coordination environment geometry around the central europium(III) ion is a distorted square antiprism in both polymorphs, while the peripheral methoxy and tolyl groups show different orientations. This phenomenon indicates the occurrence of a thermally driven second-order phase trans...

In this work, we synthesized the {tris(thenoyltrifluoroacetone)pyrazino[2,3-f][1,10]phenanthroline}europium (III) complex and studied its thermal emission quenching. The crystal structure of the [Eu(tta)3(pyphen)] complex show that the europium (III) ion occupies a distorted D4d symmetry of a square antiprism site. The complex shows an absolute emission quantum yield of 43.3 ± 1.2. The temperature dependence of the photophysical properties of the complex was evaluated and indicates that the complex has potential to be applied as a lifetime based luminescent thermometer. The quenching of the luminescence as a function of temperature occurs due the energy back-transfer from the emitter state to the ligand centered triplet state. The temperature induced blue-shift in the 5D0 → 7F0 transition band indicates the presence of the electron-phonon coupling in this complex.

A cerium(III) complex, [Ce2(NA)6(H2O)4] (1) and an erbium(III) complex, [Er2(2-AMB)6(H2O)4]·3H2O (2), where NA = nicotinic acid and 2-AMB = 2-aminobenzoic acid, have been prepared and characterized by IR spectroscopy, thermogravimetric analysis and X-ray crystallography. The single crystal analysis reveals that both complexes are dinuclear. In 1, the two cerium(III) ions are bridged by carboxylate groups of four nicotinate ligands. Each cerium atom in 1 is nine-coordinate and exhibits a distorted monocapped square antiprism geometry. The Ce(III) ions are coordinated by seven oxygen atoms of the carboxylate groups and two oxygen atoms of water molecules. In 2, each Er(III) ion is eight-coordinated adopting a distorted ErO8 dodecahedral geometry. The Er(III) ions are bound to four oxygen atoms of the chelating carboxylate ligands, to one oxygen each from the two bridiging carboxylates, and two oxygen atoms of water molecules. In 2 there is an intramolecular hydrogen bond forming a six-membered ring between the NH2 group and one of the carboxylate oxygens in each of the six 2-AMB ligands. In the crystal packing, the molecules of 1 and 2 are associated through O(or N)–H⋯O and O–H⋯N hydrogen bonds. In 2 the intermolecular hydrogen bonding results in a 3D supramolecular network structure.

Three dinuclear complexes, [Tb2(H2daps)2(CH3OH)5.5(H2O)0.5](Cl)2 (Tb2Cl), [Dy2(H2daps)2(Cl)(CH3OH)3(H2O)]Cl (Dy2Cl), and [Dy2(H2daps)2(H2O)6](CF3SO3)2 (Dy2CF3SO3), as well as the heterohexanuclear compound [Zn2Dy4(daps)2(Hdaps)(Cl)3(OH)2(CH3OH)(H2O)5] (Zn2Dy4) (H4daps: 2,6-bis(1-salicyloylhydrazonoethyl)pyridine), which crystallize with different lattice molecules, show their hexa- or heptadentate hydrazone ligands acting with hitherto unknown μ2-κ5:κ1, μ3-κ5:κ4:κ1, μ4-κ5:κ4:κ1:κ1, or μ4-κ5:κ2:κ1:κ1 bridging modes. The single X-ray crystal structures of the dinuclear complexes show nine-coordinated N3 O6 environments for lanthanoid atoms in Tb2Cl and Dy2CF3SO3, with distorted geometries, between spherical capped square antiprism and muffin-like, while the dysprosium atoms in Dy2Cl are eight-coordinated, with distorted triangular dodecahedron geometries. In the case of Zn2Dy4, both eight-coordinated, O8 and O7 Cl, as well as nine-coordinated N3 O6 environments coexist in the crystal structure, with biaugmented trigonal prism, triangular dodecahedron, and muffin-like pseudogeometries. The magnetic study of all the complexes shows that none of the pure samples behaves as a single molecular magnet (SMM) and that the quantum tunnel cannot be removed by dilution of any of the dinuclear complexes, but except in diluted [Y1.904Dy0.096(H2daps)2(Cl)(H2O)4]Cl (Dy2Cl@Y), behaves as a weak field induced SMM. The heterohexanuclear Zn2Dy4 complex also lacks slow relaxation of the magnetization.

A solid state Eu3+ complex with dehydroacetic acid (DHA) has been synthesized and characterized by elemental analysis, UV–visible, FT-IR, FT-Raman, powder and single-crystal X-ray diffraction and optical spectroscopy studies. The complex has formula [Eu(DHA)2(H2O)5]NO3 with DHA = C8H7O4−, where the europium ions is in monocapped distorted square antiprism environment with coordination number nine. Its photophysical properties have been analyzed in terms of its molecular structure and DFT calculations performed for the representative crystal fragment including Eu3+ and two DHA ligands. The luminescence and dynamics of the excited states depopulation have been studied using femtosecond laser excitation. The energy transfer mechanism between the ligand and Eu3+ electronic energy levels has been proposed. The obtained results have been compared to those of Gd3+ dehydroacetic derivative.

A novel samarium compound, [Sm(Phen)2(H2O)5]2(Phen)2(Bipy)Cl6 · 7H2O (I) (Phen = 1,10-phenanthroline and Bipy = 2,2'-bipyridine), was prepared by a solvothermal reaction. The crystal structure of I was characterized by X-ray single-crystal diffraction method (CIF file CCDC no. 1025736). Compound I is an isolated structure with the samarium ions possessing a nine-coordinated distorted monocapped square antiprism geometry. There are abundant hydrogen bonding and π–π stacking interactions which connect the molecules together to yield a three-dimensional (3D) supramolecular structure. The fluorescence spectra data reveals that I can display the characteristic emission 4G5/2 → 6H J transitions (J = 5/2, 7/2, 9/2 and 11/2, respectively) of Sm3+ ions.

The synthesis, crystal structures, and magnetic properties of a nonanuclear dysprosium complex [Dy9(μ3-OH)8(μ4-OH)2(N3)8{(py)2C(OCH3)O}8](OH)·4H2O (1, (py)2C(OCH3)OH = the hemiacetal form of di-2-pyridyl ketone) and a tetranuclear dysprosium complex [Dy4(μ4-O)(μ-N3)2(μ-OCH3)2(L)4](OH)2·3.5CH3OH (2, HL = 2-(benzothiazol-2-yl-hydrazonomethyl)-6-methoxyphenol) have been prepared and structural characterization. Nine DyIII ions in 1 form a sandglass with the eight DyIII atoms at the apexes and one DyIII ion located at the center of a square antiprism formed by eight DyIII ions, while four DyIII ions in 2 form an irregular tetrahedron. Complexes 1 and 2 have been investigated by direct current (dc) and alternating current (ac) susceptibility measurements. The ac susceptibility studies revealed that complexes 1 and 2 exhibit slow magnetic relaxation. Moreover, complex 2 shows two-step thermal magnetic relaxation with their energy barriers of about 15 K and 2.68 K, respectively. The orientations of the magnetic anisotropy of DyIII ions in 1 and 2 were also estimated by electrostatic calculations.

The new lanthanide coordination compounds of general formula [LnL3Q], where Ln = Eu, Gd, Tb; L = dimethyl-N-trichloroacetylamidophosphate and Q = 2-(1,3,4-oxadiazole-2-yl)pyridine, have been synthesized and isolated in crystalline state with the purpose of finding new interesting optical materials. X-ray data reveal that complexes have molecular structure with numerous Van-der-Vaals contacts between molecules. All the ligands are coordinated in bidentate chelate manner, coordination polyhedron was interpreted as distored square antiprism (CN 8). The obtained complexes were investigated by means of IR, absorption and luminescence spectroscopy as well and thermal gravimetric analysis. It was found that complex [TbL3Q] is resistant to temperature of 200 °C. The Eu3+ and Tb3+ complexes exhibit bright metal-centered emission with decay time 1.65 and 1.74 ms respectively. Intrinsic quantum yield for [EuL3Q] equals 85% that is one of the highest values, known to date for CAPh based europium complexes.

Four mononuclear dysprosium complexes, namely, [Dy(thd)3(MeOH)2] (1), [Dy(thd)3(Phen)] (2), [Dy(thd)3(Dpq)] (3) and [Dy(thd)3(Dppz)] (4) (thd = 2,2,6,6-tetramethyl-3,5-heptanedione; Phen = 1,10-phenanthroline; Dpq = dipyrazine[2,3-f:2′,3′-h]quinoxaline; and Dppz = dipyrido[3,2-a:2′,3′-c]phenazine), have been designed and isolated by reactions of Hthd with DyCl3·6H2O and corresponding auxiliary capping ligands such as Phen, Dpq and Dppz. The crystal structure analysis exhibits that Dy(III) ions in complexes 1–4 adopt distorted square antiprism geometry with D4d symmetry. Magnetic analysis reveals that all complexes 1–4 exhibit slow magnetic relaxation with the barrier heights (Ueff/kB) of 45.1 K, 98.4 K, 128.9 K and 89.4 K, respectively. The butterfly magnetic hysteresis loops were observed up to 5 K for complex 2. The co-relationship between the barrier heights and the structure in terms of the Dy–Oβ-diketone bond lengths, the quantify distortion degree (σα2 or σΦ2) and the deviation angles (θ) of magnetic easy axes for the SAP coordination environment were investigated and discussed.

The first complexes of Ce(IV)fluoride in solution have been observed and studied by 19F{1H}, 1H NMR and IR spectroscopy in saturated solutions of CeF4*H2O in Me2SO diluted by CH3CN or CH2Cl2. On the base of analysis of the temperature dependence of the 19F{1H} NMR spectra and the assumption that the usual for the solid Ce(IV) fluorocomplexes square antiprism coordination polyhedron is retained in the solution, the conclusion has been made that dynamic equilibrium between the molecular adduct [CeF4(Me2SO)4] and ionic forms [CeF3(Me2SO)5]+ and [CeF5(Me2SO)3]− exists in solution, including geometric isomers. The statistical probability of formation of [CeF4(Me2SO)4] and [CeF5(Me2SO)3]− stereoisomers has been calculated. Quantum chemical calculations of the structures of some visually distinguishable isomers of [CeFn(Me2SO)8-n]4-n (n=3–5) and [CeF4(Me2SO)3(H2O)] showed their thermodynamic stability. The experimental IR spectrum of the solution is in a good agreement with calculated spectra of [CeFn(Me2SO)8-n]4-n and [CeF4(Me2SO)3(H2O)] stable complexes.

Polymeric terbium(III) squarate hydrate [{Tb2(C4O4)3(H2O)8}n] was prepared from TbCl3 or Tb2O3 and squaric acid. The crystal structure was determined in a monoclinic Pc space group, and the whole molecular arrangement gives a sandwiched two-dimensional structure. The coordination polyhedra are described as a square antiprism. The solid complex emits green light under UV irradiation at room temperature with the quantum yield of 25%. Although Tb3+ is a non-Kramers ion, the alternating-current magnetic susceptibility showed frequency dependence in a 2000-Oe DC field, and the effective energy barrier for magnetization reorientation was 33(2) K. Thus, [{Tb2(C4O4)3(H2O)8}n] displayed functions of a potential luminescent magnet.

The lanthanide-doped materials have been widely used. The well shielded f orbitals make the f-f transitions be sharp lines and non-tunable which are hurdles to the generation of ultrashort lasers. In the work, the spectral properties of neodymium-doped fluorite crystal are modulated to be varied significantly with the compositions of the crystal. The first principles calculation is combined and the results show that there exist two types of centers of cubic and square antiprism sublattice clusters. The concentrations of the centers could be tuned in large scale by adjusting the compositions of the host. Then tunable broadband photoluminescence is obtained which is promising for the generation of ultrashort pulses. The designing of new ultrafast laser materials is highly expected in the rare-earth-doped fluoride crystals.

A series of zirconium (IV) Schiff-base complexes formulated as [Zr (L x ) 2 ] and [Zr (L x ′) 2 ] were synthesized by reaction of tetradentate salicylaldimine Schiff-base ligands with [Zr (acac) 4 ] in methanol. These ligands are as follows: H 2 L x and H 2 L x ′ (x = x′ = 1,2,3,4). The new complexes have been characterized using FT-IR, l H NMR, 13 C{ 1 H} NMR spectroscopic techniques, elemental analyses (CHN) and the crystal structure of Zr (L 3 ) 2 , Zr (L 1′ ) 2 and Zr (L 3′ ) 2 were determined by X-ray crystallography. The crystal structure analysis revealed that the coordination environment of the metal in all complexes is eight-coordinate occupied by N 2 O 2 sets of the coordinated ligands in distorted square-antiprism geometry. The in vitro biological screening effects of the synthesized compounds were tested against different microbial kinds and the zirconium (IV) complexes exhibit antimicrobial activity.

The structure and thermal properties of a novel zirconium(IV) complex with a methoxy substituted β-diketonate ligand tetrakis-(2-methoxy-2,6,6-trimethylheptane-3,5-dionato)zirconium are described. The complex sublimes without decomposition under low pressure (10–2 Torr) at 200 °C. The crystal structure of the complex is molecular and is composed of two structural Zr(zis)4 isomers in a 1:1 ratio. The crystallographic data are as follows: C88H152F24O24Zr2, P-1, a = 12.1350(7) A, b = 19.7733(10) A, c = 21.0526(12) A, α = 83.338(2)°, β = 89.571(2)°, γ = 73.515(2)°, V = 4809.5(5) A3, Z = 2, d = 1.227 g/cm3. The coordination environment of the zirconium atom consists of eight oxygen atoms from four β-diketonate ligands; the coordination polyhedron is a square antiprism. The Zr–O distances are in a range 2.127-2.202 A. The thermal properties of the complex are studied by TG–DTA. The effect of the crystal structure (molecular packing) on the volatility and thermal properties is compared for the new complex and two other analogous zirconium complexes with β-diketonate ligands containing bulky terminal substituents. The results of the mass spectrometric study of thermal behavior of the complexes on programmed heating of vapor under the conditions similar to those in a hot wall CVD reactor under low pressure, including the decomposition in the presence of oxygen, are discussed.

Two Dy compounds, [Dy2(Phen)2(CH3COO)6] (1; Phen = 1,10-phenanthroline) and [Dy(Phen)2(NO3)3] (2), were obtained by the reactions of Phen with different dysprosium salts containing different anions, which act as bridging groups and greatly affect the coordination polyhedra of the metal ions. In the former complex, the DyIII ions are bridged by acetate anions and adopt a spherical capped square antiprismatic (C4v) coordination environment, whereas a bicapped square antiprism (D4d) was observed for 2, in which the DyIII ions are bridged by nitrate anions. Static and dynamic magnetic measurements revealed that both compounds display slow magnetic relaxation but with fast quantum tunneling of magnetization (QTM). In an applied direct-current (dc) field, the QTM was suppressed, and two slow magnetic relaxation processes occurred for both compounds. Comparative studies on the magnetic properties indicate how the ligand field and the local geometric symmetry of the magnetic anisotropy of the DyIII center leads to differing magnetic behavior.

Two β-diketone mononuclear Dy(III) compounds, formulated as Dy(BTFA)3(H2O)2 (1) and Dy(BTFA)3(bpy) (2) (BTFA = 3-benzoyl-1,1,1-trifluoroacetone, bpy = 2,2′-bipyridine), were prepared. Compound 1 can be identified to transform to 2 in the attendance of bpy coligand, when the local geometry symmetry of eight-coordinated Dy(III) ion changes from a dodecahedron (D2d) in 1 to a square antiprism (D4d) in 2. Fine-tuning structure aroused by auxiliary ligand has dramatical impact on magnetic properties of compounds 1 and 2. Magnetic investigations demonstrate that both 1 and 2 display dynamic magnetic relaxation of single-molecule magnets (SMMs) behavior with different effective barriers (ΔE/kB) of 93.09 K for 1 under zero direct-current (DC) field as well as 296.50 K for 1 and 151.01 K for 2 under 1200 Oe DC field, respectively. As noticed, compound 1 possesses higher effective barrier than 2, despite 1 exhibiting a lower geometrical symmetry of the Dy(III) ion. Ab initio studies reveal that the Kramers doublet ...

The structures and stabilities of K+Xen (n ≤ 54) clusters are theoretically studied using the potential model and unconstrained global optimisation. The potential energy of these systems is described in terms of pair-additive functions, with and VXe–Xe representing the pair potential interactions, complemented by the three-body contributions. We show that the three-body contributions stabilise the bent or three-dimensional structures versus the linear or planar shapes for n < 4. For n ≥ 22, the growth around the icosahedral (ICOS) core is favoured while the square antiprism (SA) or capped square antiprism (CSA) pattern-based isomers exist but not as the lowest ones. Also, we show the presence of mixed (ICOS-SA) or (ICOS-CSA) isomer structures. Finally, a transition in the metal ion coordination from 10 (ICOS-SA) to 12 (ICOS) is seen to occur near n = 22, which is obtained for the first time at this little number. Indeed, for Na+Arn and Na+Xen systems, a transition from 8 (SA) to 12 (ICOS) has been...

Mononuclear complexes of stoichiometry [Ln(H3L)(H2O)(NO3)](NO3)2 (Ln = Tb, 1; Dy, 2, Er, 3), which crystallise with different solvates, and the heterotrinuclear compound [Zn2Dy(L)(NO3)3(OH)] (4) can be obtained with the same H3L compartmental ligand. The single X-ray crystal structure of the mononuclear complexes shows a LnO9 core with a muffin-like disposition while the geometry of the DyO9 core in 4 seems to be closer to spherical capped square antiprism. The analysis of the magnetic properties of all the complexes demonstrates that the mononuclear lanthanide compounds do not show slow relaxation of the magnetization, even when the samples are diluted with a diamagnetic matrix and subjected to a dc applied field of 1000 Oe. Nevertheless, the heterotrinuclear dysprosium complex 4·3H2O is a field-induced single ion magnet, with an estimated Ueff barrier of 59 K. The luminescence characterisation of all the metal complexes in methanol solution at 298 K also shows a notable increase in the fluorescence emission of the heterotrinuclear complex with respect to the mononuclear ones, in such a way that 4 can be defined as a fluorescent single ion magnet.

We report the design, preparation and characterisation of three small-molecule, Formyl Peptide Receptor (FPR)-targeted lanthanide complexes (Tb·14, Eu·14 and Gd·14). Long-lived, metal-based emission was observed from the terbium complex (τH2O = 1.9 ms), whereas only negligible lanthanide signals were detected in the europium analogue. Ligand-centred emission was investigated using Gd·14 at room temperature and 77 K, leading to the postulation that metal emission may be sensitised via a ligand-based charge transfer state of the targeting Quin C1 unit. Comparatively high longitudinal relaxivity values (r1) for octadentate metal complexes of Gd·14 were determined (6.9 mM−1 s−1 at 400 MHz and 294 K), which could be a result of a relative increase in twisted square antiprism (TSAP) isomer prevalence compared to typical DOTA constructs (as evidenced by NMR spectroscopy). In vitro validation of concentration responses of Tb·14via three key neutrophil functional assays demonstrated that the inflammatory responses of neutrophils (i.e. chemotaxis, transmigration and granular release) remained unchanged in the presence of specific concentrations of the compound. Using a time-resolved microscopy set-up we were able to observe binding of the Tb·14 probe to stimulated human neutrophils around the cell periphery, while in the same experiment with un-activated neutrophils, no metal-based signals were detected. Our results demonstrate the utility of Tb·14 for time-resolved microscopy with lifetimes several orders of magnitude longer than autofluorescent signals and a preferential uptake in stimulated neutrophils.

Protonation of a distant, noncoordinated group of metal-based magnetic resonance imaging contrast agents potentially changes their relaxivity. The effect of a positive charge of the drug on the human serum albumin (HSA)-drug interaction remains poorly understood as well. Accordingly, a (dibenzylamino)methylphosphinate derivative of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) was efficiently synthesized using pyridine as the solvent for a Mannich-type reaction of tBu3DO3A, formaldehyde, and Bn2NCH2PO2H2 ethyl ester. The ligand protonation and metal ion (Gd3+, Cu2+, and Zn2+) stability constants were similar to those of the parent DOTA, whereas the basicity of the side-chain amino group of the complexes (log KA = 5.8) was 1 order of magnitude lower than that of the free ligand (log KA = 6.8). The presence of one bound water molecule in both deprotonated and protonated forms of the gadolinium(III) complex was deduced from the solid-state X-ray diffraction data [gadolinium(III) and dysprosium(III)], from the square antiprism/twisted square antiprism (SA/TSA) isomer ratio along the lanthanide series, from the fluorescence data of the europium(III) complex, and from the 17O NMR measurements of the dysprosium(III) and gadolinium(III) complexes. In the gadolinium(III) complex with the deprotonated amino group, water exchange is extremely fast (τM = 6 ns at 25 °C), most likely thanks to the high abundance of the TSA isomer and to the presence of a proximate protonable group, which assists the water-exchange process. The interaction between lanthanide(III) complexes and HSA is pH-dependent, and the deprotonated form is bound much more efficaciously (∼13% and ∼70% bound complex at pH = 4 and 7, respectively). The relaxivities of the complex and its HSA adduct are also pH-dependent, and the latter is approximately 2-3 times increased at pH = 4-7. The relaxivity for the supramolecular HSA-complex adduct ( r1b) is as high as 52 mM-1 s-1 at neutral pH (at 20 MHz and 25 °C). The findings of this study stand as a proof-of-concept, showing the ability to manipulate an albumin-drug interaction, and thus the blood pool residence time of the drug, by introducing a positive charge in a side-chain amino group.

The lowest energy structure of Li15 cluster is a capped double centred square antiprism sharing a square face. Interestingly, when a lithium atom is substituted by a transition-metal atom T...

One coordination polymer {[Dy(BTTA)1.5(H2O)4.5]n (Dy-1) was successfully obtained via solvo-thermal reaction of Dy(NO3)3⋅6H2O and 2,5-bis-(1H-1,2,4-triazol-1-yl)terephthalic acid (H2BTTA). Single-crystal X-ray diffraction analysis shows that the complex exhibits two-dimensional lay-by-lay structure with one-dimensional channels along b direction, while DyIII ion exhibited as distorted spherical capped square antiprism (C4v) finished by nine oxygen atoms from three BTTA ligands and five water molecules. Magnetic studies show that both of the Orbach and Raman processes contribute to the magnetic relaxation behavior of Dy-1 under low temperature.

The coordination chain {[Dy(dbm)3bpy]·C7H8}n (1) having only 4,4′-bipyridine as connector has been prepared in high yield and its structural and magnetic properties have been investigated. It is isostructural with the terbium analogue {[Tb(dbm)3bpy]·C7H8}n (2) and features units repeating in a 1D-zigzag fashion, where the metal is octa-coordinated in a distorted square antiprism geometry. Despite the 1D structure, the absence of paramagnetic connectors prevents the direct magnetic intrachain interaction among the lanthanide ions. In zero magnetic field, only a small fraction of the magnetization of 1 displayed slow dynamics with no dependence on temperature. Upon application of a 1 kOe magnetic field, a relaxation process appears, compatible with a mixed Raman/Direct mechanisms. Magnetic dilution in the diamagnetic Y(III)-based analogue revealed that actually two distinct relaxation processes are active for 1, whose temperature dependence can be interpreted again with a mixed Raman/Direct relaxation model. Compound 2 displayed only in-field slow relaxation, compatible with the models employed for 1.

Lanthanide(III) complexes of general formula [La(BPAH)2(NO3)3] and [Ce(BPAH)2(NO3)(H2O)2] 2NO3.H2O (where, BPAH = 2-benzoylpyridine acetyl hydrazone), were synthesized and characterized by elemental analysis, molar conductance, IR spectroscopy and single crystal X-ray diffraction and Hirschfeld studies. The central metal ion is 12-coordinate in lanthanum complex and 10-coordinated in the cerium complex. The coordination polyhedra around the lanthanum and cerium were found to have distorted icosahedron and distorted bicapped square antiprism respectively. DNA binding and nuclease activity of these complexes were also investigated in the present work.

Three mononuclear dysprosium(III) complexes derived from three β-diketonate ligands, 4,4,4-trifluoro-1-(4-methylphenyl)-1,3-butanedione (tfmb), 4,4,4-trifluoro-1-(4-fluorophenyl)-1,3-butanedione (tffb) and 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (tfnb) as well as auxiliary ligands, 5-nitro-1,10-phenanthroline (5-NO2-Phen), DMF and 2,2'-bipyridine (bpy) have been synthesized and structurally characterized, namely [Dy(5-NO2-Phen)(tfmb)3] (1), [Dy(DMF)2(tffb)3] (2) and [Dy(bpy)2(tfnb)3]·0.5(1,4-dioxane) (3). The metal ions in 1-3 adopt an approximately square-antiprismatic (SAP) coordination environment with D4d axial symmetry. The magnetic properties of 1-3 have been investigated, displaying weak out-of-phase AC signals under a zero-DC field. With an applied DC field of 1200 Oe, the quantum tunnelling of the magnetization was suppressed in 1-3 with the pre-exponential factor τ0 = 5.3 × 10(-7) s and the effective barrier ΔE/kB = 83 K for 1 as well as the pre-exponential factor τ0 = 3.09 × 10(-7) s and the effective barrier ΔE/kB = 39 K for 3. Interestingly, for the frequency dependence of the out-of-phase (χ'') of the AC susceptibility of 2, two slow relaxation of the magnetization processes occurred under the applied magnetic field of 1200 Oe, corresponding to the fast relaxation (FR) phase and slow relaxation (SR) phase, respectively. Arrhenius analysis gave the effective energy barrier (ΔE/kB) of 55 K and the pre-exponential factor (τ0) of 8.23 × 10(-12) for the SR. It is thus very likely that the FR process in complex 2 results from QTM enhanced by dipolar interactions between the Dy ions or the presence of the applied field. The structure-property relationship of some Dy(III) based mononuclear SMMs with the SAP configuration was further discussed.

Near-infrared (NIR) Ytterbium(ΙΙΙ) complexes namely [Yb(dpq)(DMF)2Cl3] (1), [Yb(dppz)(DMF)2Cl3] (2), [Yb(dpq)(ttfa)3] (3) and [Yb(dppz)(ttfa)3] (4) based on photosensitizing antenna: dipyrido-[3,2-d:2′,3′-f]-quinoxaline (dpq), dipyrido-[3,2-a:2′,3′-c]-phenazine (dppz) and 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Httfa), were designed as NIR bioimaging agents utilizing cooperative upconversion luminescence (CUCL) of Yb(III). Their structures, detailed photophysical properties, biological interactions, photo-induced DNA cleavage, NIR photocytotoxicity and cellular internalization and bioimaging properties were examined. Discrete mononuclear complexes adopt a seven-coordinated {LnN2O2Cl3} mono-capped octahedron (1, 2) and eight-coordinated {LnN2O6} distorted square antiprism geometry (3, 4) with bidentate N, N-donor dpq, dppz and O,O-donor ttfa ligands. The designed Yb(III) probes (3, 4) having advantages of dual sensitizing antennae (dpq/dppz and Httfa) to modulate the desirable optical properties in NIR region for bioimaging in biologically transparent window and light-responsive intracellular damage with spatiotemporal control. The lack of inner-sphere water (q = 0), remarkable photostability, large Stokes' shifts, presence of energetically rightly poised ligand 3T states allows efficient energy transfer (ET) to the emissive 2F5/2 state of Yb(ΙΙΙ). The unique cooperative upconversion luminescence (CUCL) of Yb(III) was observed in 1–4 in the visible blue region (λem = 490 nm) upon NIR excitation at 980 nm, makes them special candidates for NIR-to-visible or NIR-to-NIR cellular imaging probes. The CUCL property of Yb(III) were observed in the discrete mononuclear complexes both in solid state and solution. We elegantly utilized this remarkable property of Yb(III) for cellular imaging application for the first time to the our knowledge including potential uses in CUC/multiphoton excitation microscopy. The complexes exhibit significant binding propensity to DNA, HSA and BSA (K ∼ 105 M−1). They effectively cleave supercoiled (SC) DNA to its nicked circular (NC) form at 365 nm via photoredox pathways. The cellular uptake studies evidently displayed cytosolic and nuclear localization of the complexes. Finally, the capability of Yb(III) complexes usage for PDT were demonstrated through significant near-IR photocytotoxicity at 980 nm CW laser. The results depicted here offers an intelligent strategy towards developing light-responsive highly photostable Yb(III) probes for NIR theranostic application in the biologically transparent phototherapeutic window.

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fchem. 2018.00420/full#supplementary-material, The coordination chemistry of dysprosium and terbium toward phosphine and arsine oxides was further explored. Thus, the new nitrate [M(NO3)3(Ph3PO)3] (M = Tb, 1; Dy, 2), [Dy(NO3)3(EtOH)(Ph3XO)2] (X = P, 3; As, 4), chloride [DyCl2(Ph3AsO)4]Cl (5), triflate [Dy(OTf)2(MePh2PO)4]OTf (6; OTf = triflate) and hexafluoroacetylacetonate [M(hfa)3(Ph3PO)2] (hfa = hexafluoroacetylacetonate; M = Tb, 7; Dy, 8) complexes were isolated and fully characterized. The crystal structures of 1·CH3CN, 2·CH3CN, 4, 5·2.75EtOH·1.25H2O, 6, 7, and 8 show MO9 cores in 1, 2, and 4, with highly distorted geometry, between spherical capped square antiprism and muffin-like, hexacoordinated environments for the dysprosium ions in 5 and 6, with octahedral geometry, and octacoordination for the lanthanoid metals in 7 and 8, with geometry closer to square antiprism. Comparison of the magnetic behavior of all the complexes allows analyzing which metal ion (Tb or Dy), phosphine or arsine oxide, or anionic ligand favor more the slow relaxation of the magnetization. Alternating current magnetic measurements show that only 2, 4, and 8 present slow relaxation of the magnetization in the presence of an external magnetic field, 8 being the complex with the highest Ueff (44.85 K) of those described herein., Financial support from Ministerio de Economía y Competitividad (MINECO, CTQ2014-56312-P), Junta de Andalucía (FQM-195 and Project of excellence P11-FQM-7756) and the University of Granada are grateful acknowledged. JC-V acknowledges Xunta de Galicia for his Ph.D. fellowship.

[Sm(H 2 O) 4 (NO 3 ) 3 ](4,4'-Hbipy) 2 (NO 3 ) 2 ( 1 ) (bipy = bipyridine) has been synthesized via hydrothermal reaction and characterized by X-ray diffraction. The title complex features an isolated structure, based on discrete 4,4'-Hbipy moieties, isolated nitrates and [Sm(H 2 O) 4 (NO 3 ) 3 ] species. The samarium ion is in a distorted bicapped square antiprism environment, coordinated by three bidentate nitrates and four coordination water molecules. The 4,4'-Hbipy moieties, isolated nitrates and [Sm(H 2 O) 4 (NO 3 ) 3 ] species are held together via hydrogen bonds and p…p interactions to form a 3-D supramolecular framework. Luminescent investigation reveals a strong emission in blue region. Optical absorption spectrum of 1 reveals the presence of an optical gap of 3.60 eV. KEY WORDS : Bipyridine, Crystal structure, Fluorescence, Hydrothermal reaction, Samarium Bull. Chem. Soc. Ethiop. 2017 , 31(3), 435-444. DOI: http://dx.doi.org/10.4314/bcse.v31i3.7

The experimentally known dibismaborane Bi 2 B 10 H 10 is a potential precursor for the synthesis of metalladibismaboranes. In this connection the CoBi 2 B n frameworks of the lowest energy cobaltadibismaboranes CpCoBi 2 B n H n ( n = 7, 8, 9) have been investigated by density functional theory. In contrast to the corresponding cobaltadiphosphaboranes CpCoP 2 B n H n , as well as the related cobaltadicarbaboranes CpCoC 2 B n H n +2 , the lowest energy CpCoBi 2 B n H n structures have a CoBi 2 triangular face. Furthermore, structures with adjacent bismuth atoms in Bi–Bi edges are energetically preferred over isomeric structures with non-adjacent bismuth atoms. The ten lowest energy structures of the 10-vertex system CpCoBi 2 B 7 H 7 within 12 kcal/mol of the global minimum have a central CoBi 2 B 7 bicapped square antiprism. Nine of the ten lowest energy 11-vertex CpCoBi 2 B 8 H 8 structures within 9 kcal/mol of the global minimum have a central CoBi 2 B 8 most spherical deltahedron; eight of these structures have a bismuth atom at the unique degree 6 vertex. The tenth low-energy CpCoBi 2 B 8 H 8 structure has a central CoBi 2 B 8 polyhedron with a trapezoidal Bi 2 B 2 face. The only structures of the 12-vertex CpCoBi 2 B 9 H 9 within 65 kcal/mol of the global minimum are the nine possible structures with a central CoBi 2 B 9 icosahedron. The four such CpCoBi 2 B 9 H 9 structures with adjacent bismuth atoms all lie in energy below their isomers with non-adjacent bismuth atoms.