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Four ternary lanthanide(III) complexes, namely [Eu(Anpp)(TTA)3] (1), [Tb(Anpp)(TTA)3] (2), [Eu(Pypp)(TTA)3] (3) and [Tb(Pypp)(TTA)3] (4), [TTA = 1,1,1-trifluoro-3-(2-theonyl)acetone, Anpp = 3-(anthracen-9-yl)-1-(pyridine-2-yl)prop-2-en-1-one, Pypp = 3-(pyren-1-yl)-1-(pyridine-2-yl)prop-2-en-1-one] were designed, synthesized and characterized by various spectroscopic techniques like FT-IR, 1H-NMR, ESI-MS, UV-Vis and spectral emission studies. [Eu(Pypp)(TTA)3] (3) was structurally characterized, showing an eight coordinated {EuN1O7} square antiprismatic geometry with one N,O-donor chalcone and three O,O-donor β-diketonate ligands. Detailed photophysical properties like excited state lifetime (τ) and hydration number (q) were determined. The presence of three TTA ligands inhibits non-radiative deactivation with lifetimes in H2O in the range of 0.306–0.445 ms. The calculated hydration number (q) values (0.37–0.63) from the excited state lifetime measurements show the absence of any bound H2O molecules in the coordinatively saturated complexes (q < 1). Complexes 1–4 were studied for their biological interactions with DNA and protein and their DNA photocleavage activity was investigated. The binding constants with CT-DNA (Kb = 1.15–8.8 × 105 M−1) and HSA (KHSA = 6.5–8.1 × 105 M−1) of complexes 1–4 show their significant affinity towards these biological targets. Incorporation of chalcone ligands containing anthracene or pyrene as a photosensitizing moiety in these complexes were effective in generating reactive oxygen species (ROS). Complexes 1–4 display moderate photocleavage of supercoiled (SC)-DNA to its nicked circular (NC) form on exposure to UV-A light of 365 nm through the generation of singlet oxygen (1O2) and hydroxyl radicals (˙OH) under physiological conditions.

A new series of heterometallic trinuclear Cu2Ln complexes [lanthanide ions Ln = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5)] has been synthesized using a Cu(II)-metalloligand derived from a N2O2 donor unsymmetrical Schiff base, H2L (where H2L = N-α-methylsalicylidene-N′-salicylidene-1,3-propanediamine), and structurally characterized. Among these complexes, [(CuL)2Gd(NO3)3(CH3CN)2] (1), [(CuL)2Tb(NO3)3(CH3CN)2] (2) and [(CuL)2Dy(NO3)3(CH3CN)2] (3) are isomorphic and isostructural. In these complexes two metalloligands coordinate to the central Ln(III) (Ln = Gd, Tb and Dy respectively) ion in a transoid fashion via μ2-phenoxido oxygen atoms. The Ln(III) ions are deca-coordinated with a distorted tetradecahedron geometry. The two terminal Cu(II) ions of the complexes possess a hexa-coordinated distorted octahedral geometry. In contrast, in complexes [(CuL)2Ho(NO3)3(CH3CN)], (4) and [(CuL)2Er(NO3)3(CH3CN)]·0.5(CH3CN) (5), the two metalloligands coordinated to the Ln(III) ions in a cisoid fashion. The Ho(III) ion in 4 is nona-coordinated with a distorted tricapped trigonal prismatic geometry and the Er(III) ion in 5 is octa-coordinated with a distorted square antiprismatic geometry. The two terminal Cu(II) ions in complexes 4 and 5 are penta-coordinated with a distorted square-pyramidal geometry. The dc magnetic susceptibilities and field dependent magnetization measurement of complex 1 reveal the occurrence of ferromagnetic interactions between Cu(II) and Gd(III) ions as well as intermolecular antiferromagnetic interactions. Both complexes 2 and 3 show ferromagnetic interactions between Cu(II) and Ln(III) ions. The ac magnetic susceptibilities of all the complexes were also recorded and it was found that only complexes 2 and 3 exhibit slow relaxation of magnetization reorientation below 10 K at 2000 Oe applied dc field, this being characteristic of single molecule magnets.

Reactions of DyCl3·6H2O or Dy2O3 with 2-quinolinecarboxylic acid (H-QLC) yielded two compounds, namely, [Dy4(QLC)12(H2O)6]·4H2O (1) and [Dy(QLC)3(H2O)2]n (2). Compound 1 is a linear tetranuclear structure with one central [Dy2(QLC)4(H2O)4] subunit and two terminal [Dy(QLC)3(H2O)] subunits linked by bridging QLC− ligands. Compound 2 has a one-dimensional (1D) chain wherein the [Dy(QLC)2] unit formed by two QLC− ligands chelating a Dy(III) ion is connected by the bridging QLC− ligands. Compounds 1 and 2 exhibit slow magnetic relaxation behaviour in the absence of a static magnetic field, which is rarely observed in lanthanide-carboxylate compounds. During the structural evolution from a linear Dy4 cluster of 1 into a 1D chain of 2, the anisotropy energy barrier (Ueff) is enhanced from 45.4(2) to 144.2(1) K. Though the Dy(III) centers in 1 and 2 all are eight-coordinated with square antiprismatic coordination environments, the higher energy barrier observed for 2 could be the result of a more favorable crystal field for the Dy(III) ions in 2.

Five novel lanthanide complexes [Ln 2 (2-ClQL) 6 (phen) 2 (H 2 O) 2 ]·2H 2 O (Ln = Pr(1), Sm(2), Eu(3), Ho(4), Er(5)); 2-ClQL: 2-chloroquinoline-4-carboxylate; phen: 1,10-phenanthroline; were synthesized by conventional solution method at room temperature and characterized via elemental analysis, powder x-ray diffraction, Infrared spectroscopy and Raman spectrometry. The results indicate that complexes 1–5 are isostructural, and each Ln 3+ ion is eight-coordinated adopting a distorted square antiprismatic molecular geometry. Binuclear complex 1 are stitched together via hydrogen bonding interactions to form 1D chains, and further to form 2D sheets by the π-π interactions. Luminescence investigation reveals that complex 3 displays strong red emission. TG/DTG-FTIR, reveal the thermal decomposition processes and products of title complexes. The bacteriostatic activities of the complexes were evaluated against Candida albicans , Escherichia coli , and Staphylococcus aureus .

Two new actinide metal-organic frameworks were constructed by using a tripodal flexible ligand tris (2-carboxyethyl) isocyanurate (H3tci) under hydrothermal condition. The combination of H3tci and uranyl nitrate hexahydrate in aqueous solution leads to the isolation of [(UO2)2(H2O)4]0.5(tci)2(UO2)4(OH)4·18H2O (1), which contains two distinct UO22+ coordination environments. Four uranyl cations, linked through μ3-OH respectively, result in the edge-sharing ribbons. Then, the layer structure is constructed by U-O clusters linked through other eight-coordinated uranyl unions, giving rise to a porous structure in the space. Topological analysis reveals that complex 1 belongs to a (4, 8)-connected net with a schlafli symbol of (34.26.3)2(34.46.56.68.73.8). Th3(tci)2O2(OH)2(H2O)3·12H2O (2) generated by the reaction of H3tci and thorium nitrate tetrahydrate, possesses nine-fold coodinated Th(IV) centers with a monocapped square antiprismatic geometry. The hexamers “Th6O4(OH)4” motifs are connected together by the carboxylate groups, showing a three-dimensional structures. Complex 2 takes on an 8-connected architecture and the point symbol is (424.64).

The new ligand HPDO3MA [(R,R,R,R)-10-(2-hydroxypropyl)-α,α',α''-trimethyl-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid] was designed to combine and optimize the chemical properties of the macrocyclic ligands HPDO3A and DOTMA. The presence of the methyl groups on the acetic pendant arms of HPDO3A is expected to rigidify the structure of the ligand and favor an increase of the kinetic inertness of the Ln complexes. 1 H NMR spectra of Eu(HPDO3MA) displayed the presence of two pairs of diastereoisomers: SAP (square antiprismatic) and TSAP (twisted square antiprismatic) isomers (56 and 44 %, respectively). In addition, 1 H and 17 O relaxometric NMR studies of Gd(HPDO3MA) showed approximately a 10 % increase in relaxivity and a faster water exchange rate with respect to Gd(HPDO3A). Moreover, a detailed chemical exchange saturation transfer (CEST) characterization of Yb(HPDO3MA) displayed a sensitivity about two times larger than that of Yb(HPDO3A) both in phantom and in cell labeling experiments. Finally, the kinetic inertness of Yb(HPDO3MA) was measured to be twice as high as that of Yb(HPDO3A), with a dissociation half-life at physiological pH of about 2500 years.

By means of a solvothermal reaction of isonicotinic acid and europium perchlorate, a novel europium(III) complex, i.e. catena-[tri(μ2-isonicotinato-O,O′)-(biaqua-europium(III))-(triperchlorate)-(monohydrate)], [Eu(HIA)3(H2O)2]n·3n(ClO4)·nH2O (1; HIA ​= ​isonicotinic acid), was obtained. The molecular structure of complex 1 was characterized by single-crystal X-ray crystallography. Complex 1 crystallized in the space group Pī of the triclinic system with a ​= ​9.5500(2), b ​= ​10.9680(3), c ​= ​15.1214(4) A, α = 104.299(2)°, β = 91.532(2)°, γ = 111.310(2)°, V ​= ​1417.92(6) A3, C18H21Cl3EuN3O21, Mr ​= ​873.69, Z ​= ​2, Dc ​= ​2.046 ​g/cm3, μ(MoKα) ​= ​2.595 ​mm−1 and F(000) ​= ​864. The europium(III)) ions are coordinated by eight oxygen atoms (of which six come from six HIA ligands and two come from two water molecules) and displays a EuO8 square antiprismatic geometry. The adjacent europium(III) ions are interlinked by four or two μ2-bridging HIA ligands to generate an infinite one-dimensional (1-D) –Eu–(HIA)4–Eu–(HIA)2–Eu–(HIA)4–Eu– chain running along the a axis. The chains are further connected by π···π stacking and hydrogen bonding interactions to yield a three-dimensional (3-D) supramolecular network. Complex 1 exhibits red photoluminescence emission bands at 593 ​nm, 617 ​nm and 699 ​nm, which are originated from the 5D0 → 7F1, 5D0 → 7F2 and 5D0 → 7F4 characteristic transitions of europium(III) ions. It has CIE chromaticity coordinates of (0.5742, 0.3275). A solid-state UV/Vis diffuse reflection spectrum shows that complex 1 has a band gap of 5.02 ​eV with a direct transition process.

Five new lead(II) complexes {[Pb(DOTAM)](OTf)2 (1a), [Pb(TETAM)](OTf)2·2H2O (2a), [Pb(TETAM)](ClO4)2·2.8H2O (2b), [Pb(TRITAM)]2(OTf)4 (3a), [Pb(TRITAM)](ClO4)2·nH2O (3b, n = 2.3 or 2.4)} with amide-appended tetraazamacrocyclic ligands were synthesized and characterized structurally, spectroscopically and thermogravimetrically. The crystal structures were solved based on the single-crystal X-ray diffraction and were compared with molecular geometries obtained from the DFT B3LYP/LANL2DZ,6-31G(d,p) calculations. The dimeric [Pb(TRITAM)]24+ (3a) and monomeric [Pb(TRITAM)]2+ (3b) complexes were obtained by reactions of lead(II) triflate and perchlorate with TRITAM. For the other ligands, the monomeric cationic complexes were only obtained. The total coordination number of the lead(II) ion is nine in 3a and eight in the remaining compounds. The coordination polyhedrons around the metal center adopt distorted mono-capped square antiprismatic and square antiprismatic geometries. The complexes were analyzed by FT-IR and UV–Vis techniques. UV–Vis and IR spectra of three simple cationic complexes were also simulated by DFT and TD-DFT calculations. TD-DFT simulations indicated that the lowest energy absorption band is mainly due to the 6s → 6p transition within the lead(II) ion. TGA studies demonstrated high thermal stability of the studied complexes which are stable even to about 300 °C.

One monocapped square-antiprismatic Ba(II) coordination polymer [Ba4(L)2(H2O)8·H2O]n (Ba-CP1, H4L ​= ​1,1’-(1,4-phenylenebis(methylene))bis(1H-pyrazole-3,5-dicarboxylic acid), was designed and synthesized via self-assembly processes. Structure of the complex was characterized by X-ray single crystal analysis, with features of Ba–O metal-inorganic chains linked to carboxylate oxygen atoms from a six-dentate flexible chelating ligand to construct a complicated 3D Ba-metal-organic framework. Optically, luminescent investigations show that this Ba-CP is an excellent CP-based fluorescent probe, with high sensitivity for environmentally relevant Fe3+ and Cr2O72− ions. This is the first Ba-CP dual-responsive fluorescent material recognizing Fe3+ or absorbing Cr2O72− ions in DMF solution.

Two novel mononuclear lanthanide complexes, [Ln(2,4-DClBA)3(terpy)(H2O)]·H2O (Ln = Dy(1), Er(2)); 2,4-DClBA: 2,4-dichlorobenzoate; terpy: 2,2′:6′,2″-terpyridine; have been synthesized and characterized by single-crystal and powder X-ray diffraction. The results reveal that complexes 1–2 are isomorphous, and each Ln3+ ion is nine coordinated adopting a distorted monocapped square antiprismatic molecular geometry. Mononuclear complexes 1–2 are stitched together via Cl–π and hydrogen bonding interactions to form the 1D, 2D, 3D supramolecular structures, which the 3D is rarely observed. Thermal decomposition mechanism is determined by TG/DSC-FTIR, and the 3D stacked plots for the FTIR spectra of the evolved gases were recorded. Heat capacities of complexes 1–2 were measured, and the derived thermodynamic functions (H T − H 298.15), (S T − S 298.15) and (G T − G 298.15) of the complexes relative to the standard reference temperature 298.15 K were obtained. The activation energy E values of the first decomposition stage for title complexes were calculated by integral isoconversional nonlinear (NL-INT) and Starink methods. Complex 1 shows the characteristic emission of Dy3+ with strong yellow emission.

The synthesis, crystal structure, and spectral characteristics (IR, Raman, and 1H and 13C NMR) of a monomeric hexa(aqua)calcium compound, viz. [Ca(C7H5O4)2(H2O)6]·H2O (C7H5O4 = 2,5-dihydroxybenzoate), are reported. The central Ca(II) located on a twofold axis is eight coordinate in an approximate square antiprismatic environment, bonded to two monodentate 2,5-dihydroxybenzoate ligands via the carboxylate oxygen, and six waters. The adjacent monomeric units are linked with the aid of several O–H⋯O hydrogen bonds.

The introduction of 4-bromopyridine (4-Brpy) to a self-assembled MII-[NbIV(CN)8] (M = 3d metal ion) coordination system results in the formation of three-dimensional cyanido-bridged networks, {[MII(4-Brpy)4]2[NbIV(CN)8]}·nH2O (M = Zn, n = 1, 1; M = Mn, n = 0.5, 2; M = Ni, n = 2, 3). All these compounds are coordination frameworks composed of octahedral [MII(4-Brpy)4(μ-NC)2] complexes bonded to square antiprismatic [NbIV(CN)8]4– ions bearing four bridging and four terminal cyanides. 1 and 2 crystallize in the chiral I4122 space group as the mixture of two enantiomorphic forms, named 1(+)/1(−) and 2(+)/2(−), respectively. The chirality is here induced by the spatial arrangement of nonchiral but sterically expanded 4-Brpy ligands positioned around MII centers in the distorted square geometry, which gives two distinguishable types of coordination helices, A and B, along a 4-fold screw axis. The (+) forms contain left handed helices A, and right handed helices B, while the opposite helicity is presented in the...

Two novel lanthanide complexes, (EnH)[LuIII(Egta)] · 2H2O (I) and (EnH2)[YIII(Egta)H2O]2 · 6H2O (II), where En = ethylenediamine and H4Egta = ethyleneglycol-bis-(2-aminoethylether)-N,N,N′,N′-tetraacetic acid, have been successfully synthesized through direct heating reflux and their molecular crystal structures were determined by FT-IR spectroscopy, thermal analysis and single crystal X-ray diffraction techniques (CIF files CCDC nos. 966211 (I) and 966210 (II)). X-ray diffraction reveals that I has a eight-coordinate mononuclear structure with distorted square antiprismatic conformation. The reason that the Lu(III) adopts a eight-coordinate conformation is the small ionic radius and more f-orbital electrons, which generates a relatively small coordination number. Complex I crystallizes in a orthorhombic system with Pca21 space group. The crystal data are as follows: a = 22.4933(14), b = 9.1067(7), c = 10.6450(5) A and V = 2180.5(2) A3. Complex II takes nine-coordinated structure with a monocapped square antiprism, and crystallizing in the monoclinic crystal system with P21/c space group. The cell dimensions are as follows: a = 12.9600(11), b = 12.6209(12), c = 16.9151(15) A, β = 122.021(2)° and V = 2345.8(4) A3. Each ethylenediammonium (EnH 2 2+ ) cation in (EnH2)[YIII(Egta)H2O]2 · 6H2O (II) connects three adjacent [YIII(Egta)(H2O)] 2 2- anions through hydrogen bonds. While in II, there are two types of EnH 2 2+ cations, which form hydrogen bonds with the neighboring [YIII(Egta)(H2O)] 2 2- anions, leading to the formation of a 2D ladder-like layer structure. The results showed that the ionic radius of rare earth metals play a crucial role in crystal and molecular structure of their complexes.

et al., A solvothermal reaction between Ln(NO)·6HO (Ln: Gd, Tb and Dy), 2-hydroxy-1-naphthaldehyde, 2-OH-naphth, and ethylenediamine, en, in MeOH in the presence of a base, NEt, led to the formation of the 1D coordination polymers [Ln(L)(MeO)(MeOH)]·MeOH (Ln = Gd (1·MeOH), Tb(2), Dy (3·MeOH); HL = 1,1′-((1E,1′E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(naphthalen-2-ol), the Schiff-base ligand derived from the condensation of 2-OH-naphth and en), while a similar reaction in an excess of NaN yielded 1D coordination polymers [Ln(L)(N)(MeO)(MeOH)] (Ln = Gd (4), Tb (5), Dy (6)). Finally, upon replacing ethylenediamine with o-phenylenediamine, o-phen, we managed to isolate the discrete dimers [Dy(L′)(MeOH)]·2MeOH (7·2MeOH) and [Gd(L′)(MeOH)]·2MeOH (8·2MeOH) (HL′ = 1,1′-((1E,1′E)-(1,2-phenylenebis(azanylylidene))bis(methanylylidene))bis (naphthalen-2-ol), the Schiff-base ligand from the condensation of 2-OH-naphth and o-phen). Polymers 1-3 describe one-dimensional chains, containing alternating seven- and eight-coordinate Ln metal centers, polymers 4-6 contain eight-coordinate lanthanide ions, while in both 7 and 8 the two Ln centers are eight- and seven-coordinate, adopting square antiprismatic and “piano-stool” geometry, respectively. The magnetocaloric properties of the three Gd analogues were determined from magnetic measurements, yielding the magnetic entropy change-ΔS = 21.8, 23.0 and 16.0 J kg K at T = 3.0 K on demagnetization of 7 T to 0, for 1, 4 and 8, respectively. The study of the magnetic properties also revealed that all three Dy analogues (3, 6 and 7) display out-of-phase signals, therefore suggesting slow magnetic relaxation, while such behaviour was not established in the Tb analogues., The research fund for CJM and ABC has been co-financed by the European Union (European Social Fund – ESF) and Greek national funds through the Operational Program “Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) – Research Funding Program: THALES. Investing in knowledge society through the European Social Fund. GL and ME thank Spanish MINECO (MAT2015-68204-R). MS, MO and TL: “Project partially supported by Wroclaw Centre of Biotechnology, programme The Leading National Research Centre (KNOW) for years 2014–2018”

Four novel lanthanide complexes, [Ln(2,4-DClBA)3(terpy)(H2O)]·H2O (Ln = Eu(1), Tb(2)); [Ln(2,4-DClBA)3(5,5′-DM-2,2′-bipy)(C2H5OH)]2 (Ln = Eu(3), Tb(4); 2,4-DClBA: 2,4-dichlorobenzoate; terpy: 2,2′:6′,2′′-terpyridine; 5,5′-DM-2,2′-bipy: 5,5′-dimethyl-2,2′-bipyridine) have been synthesized via a conventional solution method at room temperature and structurally characterized by single crystal and powder X-ray diffraction. Complexes 1–2 exhibit mononuclear lanthanide architectures and each Ln3+ ion is nine-coordinated adopting a distorted monocapped square antiprismatic molecular geometry, while complexes 3–4 exhibit binuclear lanthanide architectures in which each Ln3+ ion is eight-coordinated adopting a distorted square antiprismatic molecular geometry. Mononuclear complexes 1–2 are stitched together via Cl–π and hydrogen bonding interactions to form the 1D, 2D, 3D supramolecular structures. While complexes 3–4 are packed together through Cl–Cl, π–π, and hydrogen bonding interactions to form 1D, 2D supramolecular structures. Luminescence investigation reveals that complexes 1, 3 and 2, 4 display strong red and green emission respectively, showing that terpy and 5,5′-DM-2,2′-bipy can act as sensitizing chromophores, but the former is more effective. The IR, TG-DTG, and the heat capacities of complexes 1–4 were also measured.

Two novel rare earth metal coordination compounds, {K[SmIII(Egta)] · H2O} n (I) (H4Egta = ethyleneglycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid) and (NH4)[LuIII(Egta)] · H2O (II), have been successfully synthesized through direct heating reflux and characterized by FT-IR spectroscopy, thermal analysis and single-crystal X-ray diffraction techniques (NIF file CCDC nos. 966211 (I) and 966210 (II)). Complex I shaps a polynuclear and nine-coordinate structure with distorted monocapped square antiprismatic (MC-SAP) conformation and crystallizes in the monoclinic crystal system with space group C2/c. The central Sm3+ ion is coordinated by two nitrogens and six oxygens from one octadentate Egta ligand. Meanwhile, one oxygen atom comes from one carboxylic group of the neighboring Egta ligand, forming one dimensional unlimited polynuclear complexes. The cell dimensions are: a = 38.253(3), b = 13.7769(11), c = 8.7652(7) A, β = 100.696(2)° and V = 4539.0(6) A3. Complex (II) adopts a mononuclear structure with eight-coordinate pseudo-SAP conformation and crystallizes in the monoclinic crystal system with space group P21/c. The central Lu3+ ion is coordinated by two nitrogens and six oxygens all from one octadentate Egta ligand. The crystal data are as follows: a = 13.9817(10), b = 9.7392(6), c = 14.6305(13) A, β = 110.267(9)° and V = 1868.9(2) A3.

A linear Zn(II) complex, [Zn3(LOMe-pn)2(ƞ1-NCS)2] (1) containing a N2O2O′2 donor Schiff base, (H2LOMe-pn = N, N-bis(3-methoxysalicylidene)-2, 2-dimethylpropane-1, 3 diamine) has been synthesized and structurally well characterized. SCXRD study reveals that in 1, the asymmetric section contains two identical discrete unit and each discrete unit contains three zinc metal ions (Zn1, Zn2 and Zn3) which are crystallographic independent, two deprotonated ligands [LOMe-pn]2- and [SCN−] ions which are linked with only terminal zinc ion in a η1 mode where terminal zinc atoms (Zn1/Zn3) are distorted square pyramidal while Zn2 is square antiprismatic. All computational calculations were performed by the DFT/M06 functional level and the 6-31G * basis set in the ground state. Complex optimized structure, HOMO-LUMO energy gap, Hirshfeld surface, MEP and NLO property was nicely explained with the help of DFT. Total dipole moment, average polarizability and first hyperpolarizability were calculated where α and βhyp values are well demonstrate the NLO property of complex (1). In addition, Bader’s “atoms-in-molecules” was analysed to delineate complex non-covalent interactions using the same level of theory. Experimental electronic spectra were explained using TD-DFT level of calculations with an IEFPCM solvent model. DMF solvent explore complex (1) is a fluorescent material with maximum emission at 479 nm at an excitation wavelength of 300 nm. Finally, molecular docking was executed with cytochrome P450 from B. megaterium and M. tuberculosis. Results of molecular docking and HOMO-LUMO energy gap can provide new insights in the development of antimycobacterial drugs and next-generation semiconductor devices.

A sensitizer ligand, 1,1,1,5,5,5-Hexafluoro-2,4-pentandione (Hhfaa) is employed to synthesize two new ternary–lanthanide(III) complexes, [Ho(hfaa)3(Hind)2] and [Tm(hfaa)3(Hind)2], in which the monodentate N-donor indazole (Hind) was used as the antenna ligand. Both the complexes were characterised thoroughly. The single-crystal XRD suggests that the complexes are eight-coordinate where the metal ions are coordinated to three hfaa and two Hind ligands making the coordination polyhedra as LnO6N2 with distorted square antiprismatic geometries. The one- and two-dimensional NMR analyses confirm the eight-coordinate structures and show that the complexes are isostructural in the solution. The complexes are thermally stable up to 200 °C, which is quite suitable to find the potential application in the optoelectronic devices. Furthermore, the UV-excitation of the complexes led to characteristic emission transitions in the visible and NIR regGive a space between NIR and region on from the [Ho(hfaa)3(Hind)2] and [Tm(hfaa)3(Hind)2] complexes. The NIR luminescence, particularly 1.5 μm from the Ho complex and 1.4 μm from the Tm complex makes them potential candidates for optical communications and of broadening amplification band from C– band (1530–1560 nm) to S + band (1450–1500 nm) in optical fibre, respectively.

A series of [LnIII1.375(pydc)2(H2O)4] (Ln = SmIII (I), EuIII (II), GdIII (III), TbIII (IV), DyIII (V), HoIII (VI), ErIII (VII) and pydc2− = 2,5-pyridinedicarboxylate) were synthesized and characterized, disclosing a non-porous and highly disordering three-dimensional frameworks. The framework architecture is described based on four unique LnIII centers of two different square antiprismatic coordination spheres and discussed with reference to the closely relevant lanthanide coordination frameworks of pydc2−. Influences of the subtle change in synthesis parameters on crystallographic disordering and therefore diversity of the framework architectures are presented. The temperature-dependent photoluminescent properties of the titled complexes were studied, revealing variation in sensitization efficiency of pydc2− and the bi-exponential behavior in time-dependent luminescent decay. The influences of the crystallographic disorder in the framework structures on photoluminescent properties are demonstrated. Based on the temperature-dependent photoluminescent properties of the bimetallic [EuIIIxTbIII1.375−x(pydc)2(H2O)4] (VIII-X) and [SmIIIxTbIII1.375−x(pydc)2(H2O)4] (XI-XIII), the life times and the energy transfer efficiencies of the common TbIII-to-EuIII and the rare TbIII-to-SmIII energy transfer process have been studied. Temperature sensing performance of VIII-X and the potential of XIII as white light emitting material are also included.

Lanthanide chelating tags (LCTs) have been used with great success for determining structures and interactions of proteins and other biological macromolecules. Recently LCTs have also been used for in-cell NMR spectroscopy, but the bottleneck especially for demanding applications like pseudocontact shift (PCS) NMR is the sparse availability of suitable tags that allow for site-selective, rigid, irreversible, fast, and quantitative conjugation of chelated paramagnetic lanthanide ions to proteins via reduction stable bonds. We report here several such tags and focus on a new pyridine thiazole derivate of DOTA, that combines high affinity, rigidity, and selectivity with unprecedented tagging properties. The conjugation to the cysteine thiol of the protein results in a reductively stable thioether bond and proceeds virtually quantitatively in less than 30 min at 100 μM protein concentration, ambient temperature, and neutral pH. Upon conjugation of the new tag to two single cysteine mutants of ubiquitin and a single cysteine mutant of human carbonic anhydrase type II (30 kDa) only one stereoisomer is formed (square antiprismatic coordination, Λ(δδδδ)) and large to very large pseudocontact shifts as well as large residual dipolar couplings (RDCs) are observed by NMR spectroscopy. The PCS and RDC show excellent agreement with the solid state structure of the proteins. We believe that the pyridine thiazole moiety reported here has the potential to serve as a thiole reactive group in various conjugation applications; furthermore, its terbium complex shows strong photoluminescence upon irradiation and may thus serve as a donor group for Forster resonance energy transfer spectroscopy.

Luminescence spectroscopy has been used to monitor the selective and reversible binding of pH sensitive, macrocyclic lanthanide complexes, [LnL1], to the serum protein α1-AGP, whose concentration can vary significantly in response to inflammatory processes. On binding α1-AGP, a very strong induced circularly-polarised europium luminescence signal was observed that was of opposite sign for human and bovine variants of α1-AGP-reflecting the differences in the chiral environment of their drug-binding pockets. A mixture of [EuL1] and [TbL1] complexes allowed the ratiometric monitoring of α1-AGP levels in serum. Moreover, competitive displacement of [EuL1] from the protein by certain prescription drugs could be monitored, allowing the determination of drug binding constants. Reversible binding of the sulphonamide arm as a function of pH, led to a change of the coordination environment around the lanthanide ion, from twisted square antiprism (TSAP) to a square antiprismatic geometry (SAP), signalled by emission spectral changes and verified by detailed computations and the fitting of NMR pseudocontact shift data in the sulphonamide bound TSAP structure for the Dy and Eu examples. Such analyses allowed a full definition of the magnetic susceptibility tensor for [DyL1].

We synthesized the dinuclear and mononuclear dysprosium(III) complexes [{Dy(Tp)2}2(Cl2An)]·2CH2Cl2 (1) and [Co(Cp)2][Dy(Tp)2(Cl2An)] (3), where Cl2An2− and Tp− are the chloranilate and hydrotris(pyrazolyl)borate ligand, respectively. In addition, the magnitude of the magnetic coupling between the lanthanide centers through the Cl2An2− bridge has been probed through the synthesis of [{Gd(Tp)2}2(Cl2An)]·2CH2Cl2 (2), which is a gadolinium(III) analogue of 1. Complexes 1–3 were characterized by infrared (IR) spectroscopy, elemental analysis, single-crystal X-ray diffraction, and SQUID measurements. IR and single-crystal X-ray structural analyses confirm that the coordination environments of the lanthanide(III) centers in 1 and 3 are similar to each other; i.e., eight-coordinated metal centers, each occupied by an N6O2 donor set from two Tp− ligands and one Cl2An2− ligand. The coordination geometries of the lanthanide(III) centers in 1 and 2 are distorted triangular dodecahedral, while that in the mononuclear complex 3 is square antiprismatic, where the Cl2An2− ligand takes the bi-separated delocalized form in 1 and 2, and the o-quinone form in 3. Alternating-current (AC) magnetic studies clearly reveal that both 1 and 3 exhibit field-induced slow relaxations of magnetization that occur via Raman and direct processes. Complexes 1 and 3 exhibit different spin relaxation behavior, which reflects the coordination geometry around each DyIII center and its nuclearity, as well as the molecular packing in the crystal lattice. Although the magnetic analysis of 2 revealed negligible magnetic coupling, Cl2An2− bridges with small biases may form in the dinuclear complexes, which play roles in the spin relaxation dynamics through dipolar interactions.

A theoretical study of dysprosium(III) and holmium(III) in aqueous solution based on a quantum mechanical charge field-molecular dynamics (QMCF-MD) simulation is presented. The obtained structural and dynamical data were found to be in good agreement with several experimental and theoretical data. It is shown that the coordination number is constantly switching between eight and nine adopting square antiprismatic and tricapped trigonal prismatic configurations, thus supporting the interpretation of experimental data.

Two hexagonal series of lanthanoid(III) oxide fluoride selenides with similar structure types can be obtained by the reaction of the components MF3, M2O3, M, and Se in sealed niobium tubes at 850 °C using CsI as fluxing agent. The compounds with the lighter and larger representatives (M = La – Nd) occur with the formula M6O2F8Se3, whereas with the heavier and smaller ones (M = Nd, Sm, Gd – Ho) their composition is M2OF2Se. For both systems single-crystal determinations were used in all cases. The compounds crystallize in the hexagonal crystal system (space group: P63/m) with lattice parameters of a = 1394–1331 pm and c = 403–372 pm (Z = 2 for M6O2F8Se3 and Z = 6 for M2OF2Se). The (M1)3+ cations show different square antiprismatic coordination spheres with or without an extra capping fluoride anion. All (M2)3+ cations exhibit a ninefold coordination environment shaped as tricapped trigonal prism. In both structure types the Se2– anions are sixfold coordinated as trigonal prisms of M3+ cations, being first condensed by edges to generate trimeric units and then via faces to form strands running along [001]. The light anions reside either in threefold triangular or in fourfold tetrahedral cationic coordination. For charge compensation, both structures have to contain a certain amount of oxide besides fluoride anions. Since F– and O2– can not be distinguished by X-ray diffraction, bond-valence calculations were used to address the problem of their adjunction to the available crystallographic sites.

The quaternary thioaluminogermanates Na(AlS2)(GeS2) (1) and K(AlS2)(GeS2) (2) crystallize in the tetragonal space group I4/mcm (no. 140) with unit cell parameters a = 7.4274(11) A, c = 5.8560(12) A for Na(AlS2)(GeS2) and a = 7.8826(2) A, c = 5.8642(4) A for K(AlS2)(GeS2). The crystal structure comprises of one-dimensional [(AlS2)(GeS2)]– anionic chains with Al and Ge sharing the tetrahedral site. The alkali metal cations fill the square antiprismatic voids between chains. Both 1 and 2 are semiconductors with bandgap of around 3.6 eV and 3.5 eV, respectively.

A new type of ionic ferroelectric based on a chiral salen-type Schiff base erbium(III) complex (ErL) was synthesized by the reaction of erbium nitrate with the ligand N,N′-bis(3,5-dichlorosalicylidene)-(1S,2S)-1,2-cyclohexylenediamine (L). The structures of the ligand L and the complex ErL were determined by single-crystal X-ray diffraction. The results indicated that ErIII not only acts as central metal atom to coordinate with two Schiff base ligands, but also as Lewis acid catalyst to promote the partial decomposition of another salen-type Schiff base ligand. The central ErIII atom adopts an octacoordinate square antiprismatic arrangement with Λ absolute configuration, coordinating with all nitrogen and oxygen atoms of two ligands due to the influence of the strong electron-withdrawing group on the Schiff base ligand. The complex ErL exhibits good SHG and ferroelectric properties. The results provide a simple and effective approach to construct rare earth complexes coordinated with nitrogen and oxygen atoms of salen-type Schiff base ligands with technologically important properties such as SHG activity and ferroelectricity.

Three ternary rare earth [NdIII (1), SmIII (2) and YIII (3)] complexes based on 3-[(4,6-dimethyl-2-pyrimidinyl)thio]-propanoic acid (HL) and 1,10-phenanthroline (Phen) were synthesized and characterized by IR and UV/Vis spectroscopy, TGA, and single-crystal X-ray diffraction. The crystal structures showed that complexes 1–3 contain dinuclear rare earth units bridged by four propionate groups and are of general formula [REL3(Phen)]2·nH2O (for 1 and 2: n = 2; for 3: n = 0). All rare earth ions are nine-coordinate with distorted mono-capped square antiprismatic coordination polyhedra. Complex 1 crystallizes in the monoclinic system, space group P21/c with a = 16.241(7) A, b = 16.095(7) A, c = 19.169(6) A, β = 121.48(2)°. Complex 2 crystallizes in the monoclinic system, space group P21/c with a = 16.187(5) A, b = 16.045(4) A, c = 19.001(4) A, β = 120.956(18)°. Complex 3 crystallizes in the triclinic system, space group P1 with a = 11.390(6) A, b = 13.636(6) A, c = 15.958(7) A, α = 72.310(17)°, β = 77.548(15)°, γ = 78.288(16)°. The antioxidant activity test shows that all complexes own higher antioxidant activity than free ligands.

Six- and seven-membered cyclic hydroxamic acids, such as 1-hydroxypiperidine-2-one (1H, 1,2-PIPOH) and 1-hydroxyazepan-2-one (2H), have recently been identified in some mixed siderophores as one of their three chelating subunits. Compared to their ubiquitous noncyclic counterparts, cyclic hydroxamates are preorganized for metal binding. Surprisingly, the coordination chemistry of these bidentate, monoanionic ligands remains virtually unknown, even in the case of iron(III). We report herein the first structural study of the complexes of 1– and of 6–, an unsaturated seven-membered ring analog of 2–, with tetravalent cations of transition metals (zirconium and hafnium), lanthanide (cerium), and actinides (thorium and uranium). Structural characterization by means of X-ray crystallography of the corresponding ML4 complexes evidenced distorted square antiprismatic coordination geometries with the exception of U4+, which favors a dodecahedral arrangement.

A systematic quantum mechanical study of σ-hole (chalcogen, pnicogen, and halogen) bonding in neutral experimentally known closo-heteroboranes is performed. Chalcogens and pnicogens are incorporated in the borane cage, whereas halogens are considered as exo-substituents of dicarbaboranes. The chalcogen and pnicogen atoms in the heteroborane cages have partial positive charge and thus more positive σ-holes. Consequently, these heteroboranes form very strong chalcogen and pnicogen bonds. Halogen atoms in dicarbaboranes also have a highly positive σ-hole, but only in the case of C-bonded halogen atoms. In such cases, the halogen bond of heteroboranes is also strong and comparable to halogen bonds in organic compounds with several electron-withdrawing groups being close to the halogen atom involved in the halogen bond.

Lanthanide complexes of the form Ln(DBM)3(Cz-PBM) (where Ln = Gd(III), Tb(III) and Eu(III); DBM = dibenzoylmethane and Cz-PBM = (4-(9H-carbazol-9-yl)phenyl)methyl-2-(2′-pyridyl)benzimidazole) have been successfully synthesized and characterized. The crystal structures of the Gd(III) and Tb(III) complexes were determined by single-crystal X-ray analysis. The results reveal that in the complexes the central metal ions assume a square antiprismatic geometry and are octa-coordinated by six oxygen atoms from DBM ligands and two nitrogen atoms from the Cz-PBM ligand. Under excitation with ultraviolet light, the Eu(III) complex exhibited a strong red emission, but the Tb(III) complex did not show the characteristic emissions of the Tb3+ ion. The results show that the ligands favor energy transfers to the emitting energy level of Eu3+.

A new Er(III) β-diketonate complex, tris(dibenzoylmethanate)mono(2,2′-bipyridine) erbium(III) or [Er(dbm)3(bipy)], has been synthesized and its structural, thermal, photophysical and low temperature magnetic properties have been characterized. In the new complex, Er(III) ions are coordinated by six O atoms and two N atoms in a distorted square antiprismatic geometry. The Er(III) complex exhibits out-of-phase (χM′′) ac susceptibility signals, when a static magnetic field is applied, signaling that at zero field a quantum tunneling regime occurs. The nearly semi-circular and symmetrical shape of the Cole–Cole plots sustains the existence of a single magnetic relaxation process. The solid state luminescent studies show an intense, sharp and narrow emission band in the near infrared region. The combined results demonstrate the ability of dbm and bipy to provide an environment that yields both interesting magnetic and optical properties.

Colorless crystals of ThSiO4 (huttonite) (1) and (Ca0.5Na0.5)2NaThSi8O20 (2) have been synthesized by the solid-state reactions of ThO2, CaSiO3, and Na2WO4 at 1073 K. Green crystals of (Ca0.5Na0.5)2NaUSi8O20 (3) have been synthesized by the solid-state reactions of UO2, CaSiO3, and Na2WO4 at 1003 K. All three compounds have been characterized by single-crystal X-ray diffraction. Compound 1 adopts a monazite-type three-dimensional condensed structure, which is built from edge- and corner-shared ThO9 polyhedra and SiO4 tetrahedra. Compounds 2 and 3 are isostructural and they crystallize in a steacyite-type structure. The structure consists of discrete pseudocubic [Si8O20]8− polyanions, which are connected by An4+ cations into a three-dimensional framework. Each An atom coordinates to eight monodentate [Si8O20]8− moieties in a square antiprismatic geometry. Na+ and Ca2+ ions reside in the void within the framework. Raman spectra of 1, 2, and 3 were collected on single crystal samples. 1 displays more complex vibrational bands than thorite. Raman spectra of 2 and 3 are analogous with most of vibrational bands located at almost the same regions.

Two complexes comprising 9-coordinate capped square antiprismatic [Ln(NO3)3(OH2)2(MeOH)] units [Ln(III) = Dy 6; Tb 7] are reported in which the metal complexes are hydrogen-bonded to 15C5 (15-crown-5) macrocycles to form supramolecular chains, {[Ln(NO3)3(OH2)2(MeOH)]·(15C5)}n. Alternating current magnetic susceptibility measurements supported by ab initio studies show field-induced SMM (single-molecule magnet) behavior for 6, but rapid relaxation of the magnetization for 7 because of the presence of dominant quantum tunneling processes as evidenced by the presence of a significant calculated tunnel splitting within the ground-state multiplet. Modeling the high-resolution emission spectra for 6 afforded energies of 37 ± 5 and 28 ± 5 cm–1 for the first-excited-state Stark sublevels of the two crystallographically independent Dy1 and Dy2 ions, in excellent agreement with the calculated values of 31 and 21 cm–1 for ΔE1 derived from ab initio studies.

[Abstract] Two macrocyclic ligands containing a cyclen unit, a methyl group, a picolinate arm, and two acetate pendant arms attached to two nitrogen atoms of the macrocycle either in trans (1,7-H3Medo2 ampa = 2,2′-(7-((6-carboxypyridin-2-yl)methyl)-10-methyl-1,4,7,10-tetraazacyclododecane-1,4-diyl)diacetic acid) or in cis (1,4-H3Medo2 ampa) positions are reported. These ligands provide eight-coordination to the Ln3+ ions, leaving a coordination position available for a water molecule that occupies a capping position in the twisted square antiprismatic polyhedron (1,4-H3Medo2 ampa) or one of the positions of the square antiprism (1,7-H3Medo2 ampa). The charge neutral [Gd(1,7-Medo2 ampa)] complex presents an unprecedentedly low water-exchange rate (kex298=8.8×103 s−1), whereas water exchange in [Gd(1,4-Medo2 ampa)] is three orders of magnitude faster (kex298=6.6×106 s−1). These results showcase the labile capping bond phenomenon: A ligand occupying a capping position is hindered by the environment and thus is intrinsically labile. Ministerio de Economía y Competitividad; CTQ2009-10721/PPQ Ministerio de Economía y Competitividad; CTQ2013-43243-P Ministerio de Economía y Competitividad; CTQ2015-71211-REDT Xunta de Galicia; CN2012/011 European Commission; GINOP-2.3.2.-15-2016-00008 Hungría. Hungarian Scientific Research Fund; K-109029 Hungría. Hungarian Scientific Research Fund; K-120224

A series of diabolo-like nonanuclear {LnIIICuII8} (Ln = Tb, Dy, Ho, Er, Tm, Yb and Y) clusters in which the LnIII ion is capped by two 8-MC-4 metallacrown ligands to form a nearly ideal square antiprismatic (SAP) coordination geometry with D4d-symmetry have been prepared. Despite the lack of crystallographic symmetry these molecules engender the lanthanide ions with highly axial mJ states. We observe that the axial/equatorial nature of the crystal field in environments close to ideal SAP geometry is very subtle and influenced by the nature of the ligand lone pairs. We find slow magnetic relaxation behaviour for the DyIII, ErIII, TmIII and YbIII analogues, and show that the obtained effective energy barriers are not consistent with excitations on the LnIII ion, suggesting a more nuanced situation.

Two title rare earth metal coordination compounds, (MnH)[GdIII(Edta)(H2O)3] · 4H2O (I) and (MnH)2[Gd2III(H2Ttha)2] · 4H2O (II), where Mn = methylamine, H4Edta = ethylenediamine-N,N,N′,N′-tetraacetic acid, H6Ttha = triethylenetetramine-N,N,N′,N″,N′″,N′″-hexaacetic acid), have been successfully synthesized through direct heating reflux and characterized by FT-IR spectroscopy, thermal analysis and single-crystal X-ray diffraction techniques. In complex I, the Gd3+ ion is nine-coordinated by an Edta ligand and three water molecules, yielding a pseudo-monocapped square antiprismatic (MC-SAP) conformation. Complex I crystallizes in the orthorhombic crystal system with space group Fdd2. The cell dimensions are as follows: a = 19.5207(17), b = 35.387(3), c = 12.5118(11) A, and V = 8642.8(13) A3. The central Gd3+ ion of II is also ninecoordinate, forming tricapped trigonal prismatic (TC-TP) conformation with three amine nitrogen atoms and six oxygen atoms. Complex II crystallizes in the monoclinic crystal system with P2/c space group. The crystal data are as follows: a = 14.4301(13), b = 11.2400(11), c = 17.7102(16) A, β = 112.606(2)°, and V = 2651.8(4) A3. There retain outer-protonated and inner-protonated carboxyl oxygen atoms in the [Gd2III(H2Ttha)2]2− complex anion. In II, there are only one type of methylamine cation (MnH+) as the counter ion, which connects [Gd2III(H2Ttha)2]2− complex anions and lattice water molecules through hydrogen bonds, leading to the formation of 2D ladder-like layer structure.

The reaction of UO3 and H3PO3 at 100 °C and subsequent reaction with dimethylformamide (DMF) produces crystals of the compound (NH2(CH3)2)[UO2(HPO2OH)(HPO3)]. This compound crystallizes in space group P21/n and consists of layers of uranyl pentagonal bipyramids that share equatorial vertices with phosphite units, separated by dimethylammonium. In contrast, the reaction of phosphorous acid and actinide oxides at 210 °C produces a viscous syrup. Subsequent dilution in solvents and use of standard solution-state methods results in the crystallization of two polymorphs of the actinide acid phosphites An(HPO2OH)4 (An=U, Th) and of the mixed acid phosphite–phosphite U(HPO3)(HPO2OH)2(H2O)·2(H2O). α- and β-An(HPO2OH)4 crystallize in space groups C2/c and P21/n, respectively, and comprise a three-dimensional network of An4+ cations in square antiprismatic coordination corner-sharing with protonated phosphite units, whereas U(HPO3)(HPO2OH)2(H2O)2·(H2O) crystallizes in a layered structure in space group Pbca that is composed of An4+ cations in square antiprismatic coordination corner-sharing with protonated phosphites and water ligands. We discuss our findings in using solid inorganic reagents to produce a solution-workable precursor from which solid-state compounds can be crystallized.

The Schiff base N,N′-bis(salicylidene)-1,5-diamino-3-oxapentane (H2L) and its lanthanide(III) complexes, PrL(NO3)(DMF)(H2O) (1) and Ho2L2(NO3)2·2H2O (2), were synthesized and characterized by physicochemical and spectroscopic methods. Single crystal X-ray structure analysis revealed that complex 1 is a discrete mononuclear species. The PrIII ion is nine-coordinate, forming a distorted capped square antiprismatic arrangement. Complex 2 is a centrosymmetric dinuclear neutral entity in which the HoIII ion is eight-coordinate with distorted square antiprismatic arrangement. The DNA-binding properties of H2L and its LnIII complexes were investigated by spectrophotometric methods and viscosity measurements. The results suggest that the ligand H2L and its LnIII complexes both connect to DNA in a groove binding mode; the complexes bind more strongly to DNA than the ligand. Moreover, the antioxidant activities of the LnIII complexes were in vitro determined by superoxide and hydroxyl radical scavenging methods, which indicate that complexes 1 and 2 have OH· and O2–· radical scavenging activity.

Gas-phase measurements using mass-spectrometric techniques allow determination of the luminescence properties of selected molecular systems with knowledge of their exact composition. Furthermore, isolated luminophores are unaffected by matrix effects like solvent interactions or crystal packing. As a result, the system complexity is reduced relative to the condensed phase and a direct comparison with theory is facilitated. Herein, we report the intrinsic luminescence properties of nonanuclear europium(III) and gadolinium(III) 9-hydroxyphenalen-1-one (HPLN)-hydroxo complexes. Luminescence spectra of [Eu9(PLN)16(OH)10](+) ions reveal an europium-centered emission dominated by a 4-fold split Eu(III) hypersensitive transition. The corresponding Gd(III) complex, [Gd9(PLN)16(OH)10](+), shows a broad emission from a ligand based triplet state with an onset of about 1000 wavenumbers in excess of the europium emission. As supported by photoluminescence lifetime measurements for both complexes, we deduce an efficient europium sensitization via PLN-based triplet states. The luminescence spectra of the complexes are discussed in terms of a square antiprismatic europium/gadolinium core structure as suggested by density functional computations.

The Gd(3+)-DO3A-arylsulphonamide (DO3A-SA) complex is a promising pH-sensitive MRI agent. The stability constants of the DO3A-SA and DO3A complexes formed with Mg(2+), Ca(2+), Mn(2+), Zn(2+), and Cu(2+) ions are similar, whereas the logKLnL values of Ln(DO3A-SA) complexes are 2 orders of magnitude higher than those of the Ln(DO3A) complexes. The protonation constant (log KMHL) of the sulphonamide nitrogen in the Mg(2+), Ca(2+), Mn(2+), Zn(2+), and Cu(2+) complexes is very similar to that of the free ligand, whereas the logKLnHL values of the Ln(DO3A-SA) complexes are lower by about 4 logK units, indicating a strong interaction between the Ln(3+) ions and the sulphonamide N atom. The Ln(HDO3A-SA) complexes are formed via triprotonated *Ln(H3DO3A-SA) intermediates which rearrange to the final complex in an OH(-)-assisted deprotonation process. The transmetalation reaction of Gd(HDO3A-SA) with Cu(2+) is very slow (t1/2 = 5.6 × 10(3) h at pH = 7.4), and it mainly occurs through proton-assisted dissociation of the complex. The (1)H and (13)C NMR spectra of the La-, Eu-, Y-, and Lu(DO3A-SA) complexes have been assigned using 2D correlation spectroscopy (COSY, EXSY, HSQC). Two sets of signals are observed for Eu-, Y-, and Lu(DO3A-SA), showing two coordination isomers in solution, that is, square antiprismatic (SAP) and twisted square antiprismatic (TSAP) geometries with ratios of 86-14, 93-7, and 94-6%, respectively. Line shape analysis of the (13)C NMR spectra of La-, Y- , and Lu(DO3A-SA) gives higher rates and lower activation entropy values compared to Ln(DOTA) for the arm rotation, which indicates that the Ln(DO3A-SA) complexes are less rigid due to the larger flexibility of the ethylene group in the sulphonamide pendant arm. The fast isomerization and the lower activation parameters of Ln(DO3A-SA) have been confirmed by theoretical calculations in vacuo and by using the polarizable continuum model. The solid state X-ray structure of Cu(H2DO3A-SA) shows distorted octahedral coordination. The coordination sites of Cu(2+) are occupied by two ring N- and two carboxylate O-atoms in equatorial position. The other two ring N-atoms complete the coordination sphere in axial positions. The solid state structure also indicates that a carboxylate O atom and the sulphonamide nitrogen are protonated and noncoordinated.

Two mononuclear compounds Ln(e-urea)8(NO3)3 (Ln = Dy(1) and Tb(2)) have been urothermally synthesized by using the ethyleneurea (e-urea) as an organic ligand and a solvent. The e-urea ligand with a single donor atom is a unique ligand for coordinating to lanthanide ions, which is very different from those commonly observed polytopic ligands with suitable coordination pockets to encapsulate lanthanide(III) ions or chelating organic ligands. The lanthanide center surrounded by eight e-urea ligands is in a square antiprismatic environment with an approximate D4d local symmetry. Magnetic properties of both compounds have been investigated in detail using direct-current and alternating-current susceptibility measurements. The Dy(1) analogue displays slow magnetic relaxation behavior with an effective energy barrier of the magnetic relaxation of 37.68 K and the pre-exponential factor τ0 of 1.47 × 10−9 s in the presence of direct-current field of 2 kOe.

We report the synthesis and X-ray structural characterization of the new Er3+ ternary complex [Er(hd)3(bipy)] (where Hhd is 3,5-heptanedione and bipy is 2,2′-bipyridine) as well as its absorption/luminescent properties. X-ray analysis of the novel complex reveals its triclinic centrosymmetric structure with two symmetry independent complexes in the unit cell. Each lanthanide ion is surrounded by 6 oxygen atoms and 2 nitrogen atoms in a square antiprismatic geometry. The solid-state electronic absorption spectra and the luminescence spectrum show long-wavelength 4f–4f transitions which provide a potential use of the compound as a NIR emitting material in organic light-emitting devices (OLEDs).

Two dysprosium coordination compounds, (mnH)2[DyIII(Httha)]·3H2O (1) (H6ttha = triethylenetetramine-N,N,N′,N″,N′′′,N′′′-hexaacetic acid and mn = methylamine) and (enH2)3[DyIII(ttha)]2·9H2O (2) (en = ethylenediamine), were synthesized through direct heating and characterized by elemental analysis, FT-IR, thermal analysis, and single-crystal X-ray diffraction. X-ray diffraction analysis displays that 1 is a mononuclear nine-coordinate complex with a pseudo-monocapped square antiprismatic conformation (MCSAP) crystallizing in the monoclinic crystal system with P2(1)/c space group. The crystal data are as follows: a = 16.1363(19) A, b = 13.9336(11) A, c = 13.6619(14) A, β = 102.2490(10)°, and V = 3001.8(5) A3. There are two kinds of methylamine cation in 1. They connect [DyIII(Httha)]2−and crystal waters through hydrogen bonds, leading to formation of a 2-D ladder-like layer structure. The polymeric 2 also is a nine-coordinate structure with a pseudo-MCSAP crystallizing in the monoclinic crystal system with P...

A series of new polyoxometalate(POM)-based mononuclear lanthanide(III)-bi pyridine-N-oxide complexes, [Ln(bpyno)(4)][PMo12O40]center dot 2H(2)O (Ln = Dy (1), Tb (2), Er (3), Ho (4); bpyno = 4,4'-dimethyl-2,2'-bipyridyl-N-N'-dioxide), have been synthesized by the reactions between LnPMo(12)O(40) salts (Ln = Dy (1), Tb (2), Er (3), Ho (4)) and bpyno ligand. All compounds were characterized by elemental analyses, TG analyses, IR, powder X-ray diffraction and single-crystal X-ray diffraction. In 1-4, each mononuclear Ln center is coordinated by eight O atoms derived from four bpyno ligands, exhibiting an approximate square antiprismatic coordination geometry. Furthermore, the [Ln(bpyno)(4)](3+) units are well separated by the alpha-Keggin-type polyoxoanions. Magnetic measurements indicate that compound 1 exhibits frequency dependent ac magnetic susceptibilities indicative of slow relaxation of the magnetization. (c) 2012 Elsevier B.V. All rights reserved.

Two racemic tridentate ligands, N-[(imidazol-4-yl)methylidene]- dl -alanine (H2L dl -ala) and N-[(imidazol-4-yl)methylidene]- dl -phenylalanine (H2L dl -phe), were synthesized by the 1:1 condensation reaction of 4-formylimidazole and either of dl -alanine and dl -phenylalanine, respectively. The EuIII complexes ‘fac’-[EuIII(HL dl -ala)3]·8H2O (1) and ‘mer’-[EuIII(HL dl -phe)3]·7.75H2O (2) were synthesized by mixing the ligand and EuIII(acetate)3 n-hydrate with 3:1 M ratio in methanol and the crystal structures were determined. Compounds 1 and 2 with three tridentate ligands have ‘facial’ and ‘meridional’ geometries, respectively, while they have a tricapped trigonal prismatic (TTP) and a capped square antiprismatic (CSAP) coordination geometry, respectively. In the crystal lattice, 1 consists of enantiomers ‘fac’-[EuIII(HL d -ala)3] and ‘fac’-[EuIII(HL l -ala)3], while 2 consists of ‘mer’-[EuIII(HL d -phe)2(HL l -phe)] and ‘mer’-[EuIII(HL d -phe)(HL l -phe)2]. Compounds 1 and 2 displayed sharp emission bands based on the f−f transitions by excitation and showed a different emission pattern due to their ‘fac’- and ‘mer’-coordination geometries. The luminescence quantum yields and life times of 1 and 2 were estimated to be (Φ = 0.25 and 1.40 ms) and (Φ = 0.30 and 1.23 ms), respectively.

Two novel complexes, (EnH2)1.5[HoIII(Ttha)] · 4.5H2O (I) (En = ethylenediamine and H6Ttha = triethylenetetramine-N,N,N′,N″,N‴,N‴-hexaacetic acid) and (EnH2)[HoIII(Egta)(H2O)]2 · 6H2O (II) (H4Egta = ethyleneglycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid), were synthesized and their crystal structures were determined by single crystal X-ray diffraction techniques. Complex I has a nine-coordinate mononuclear structure with distorted tricapped trigonal prismatic conformation and crystallizes in the monoclinic crystal system with P2/n space group. The crystal data are as follows: a = 17.7541(18), b = 9.6810(10), c = 22.166(2) A, β = 118.913(2)°, and V = 3335.0(6) A3. Complex II has a mononuclear nine-coordinate structure with pseudo-monocapped square antiprismatic conformation and crystallizes in the monoclinic crystal system with P21/n space group. The crystal data are as follows: a = 12.978(8), b = 12.685(8), c = 14.905(9) A, β = 105.333(7)°, and V = 2366(2) A3. In I, there are two types of EnH 2 2+ anions. They connect to [HoIII(Ttha)]3− by hydrogen bonds leading to the formation of 3D pore structure along z axis. In II, EnH 2 2+ cation connects three adjacent [HoIII(Egta)(H2O)]− complex anions through hydrogen bonds, these hydrogen bonds lead to the formation of 2D network structure in [101] plane. The results showed that ligand structures play a crucial role in crystal and molecular structure of their complexes. In addition, the protonated (EnH 2 2+ ) cations conjugating to [HoIII(Ttha)]3− and [HoIII(Egta)(H2O)]− complex anions are reviewed, which act as an important beginning for study of Ho(III) complexes conjugating with other various amino and heterocyclic biomolecule.

Two Pb(II) complexes with 8-quinolinol (8-Quin), 5-chloro thiophene-2-carboxylic acid, and (5-CTPC)/5-bromo thiophene-2-carboxylic acid (5-BTPC) have been synthesized and characterized by IR, 13C NMR, and solid state photoluminescence spectra. The structures of [Pb(8-Quin)4](5-CTPC)2 (1) and [Pb(8-Quin)2(8-Quio)](5-BTPC) (2) [(8-Quio) = 8-quinolinolate] have been confirmed by X-ray crystallography. Both complexes crystallize in the triclinic crystal system with a space group . In 1, Pb(II) is eight coordinate by four bidentate 8-quinolinol groups, while in 2 it is six coordinate by two bidentate 8-quinolinol groups and one bidentate 8-quinolinolate group. This leads to square antiprismatic and pentagonal pyramidal geometries around Pb(II) in 1 and 2, respectively. Two of the 5-CTPC ligands in 1 and a 5-BTPC in 2 are involved in strong O–H···O hydrogen bonding in the lattice. Cl···π interactions are found in 1. The crystal structures are stabilized by weak C–H···O and π–π stacking interactions.

[Abstract] Lanthanide complexes with DOTA–tetraglycinate (DOTA-(gly)4) heavily favor the square antiprismatic (SAP) coordination isomer in aqueous solution, a structural feature that has made them useful as water-based paraCEST agents. In an effort to create amide-based paraCEST agents with rapid water exchange rates, we prepared the analogous tetraglycinate complexes with DOTMA, a ligand known to favor the twisted square antiprismatic (TSAP) coordination structures. Unexpectedly, NMR investigations show that the LnDOTMA–(gly)4 complexes, like the LnDOTA–(gly)4 complexes, also favor the SAP isomers in solution. This observation led to density functional theory (DFT) calculations in order to identify the energy terms that favor the SAP structures in lanthanide complexes formed with macrocyclic DOTA– and DOTMA–tetraamide ligands. The DFT calculations revealed that, regardless the nature of the ligand, the TSAP isomers present more negative hydration energies than the SAP counterparts. The extent to which the TSAP isomer is stabilized varies, however, depending on the ligand structure, resulting in different isomeric populations in solution. Estados Unidos. National Institutes of Health; CA115531 Estados Unidos. National Institutes of Health; EB015908 Estados Unidos. National Institutes of Health; EB004582 Estados Unidos. Robert A. Welch Foundation; AT-584 Ministerio de Economía y Competitividad; CTQ2013-43243-P Ministerio de Economía y Competitividad; CTQ2015-71211-REDT

An unbranched N3O2 ligand 2,6-bis[((2-pyridinylmethyl)oxy)methyl]pyridine (L1) was used to prepare new mononuclear heteroleptic Group 12 perchlorate complexes characterized by IR, (1)H NMR and X-ray crystallography. Racemic complexes with pentadentate L1 and one to four oxygens from either water or perchlorate bound to a metal ion were structurally characterized. Octahedral [Zn(L1)(OH2)](ClO4)2 (1) and pentagonal bipyramidal [Cd(L1)(OH2)(OClO3)]ClO4 (2) structures were found with lighter congeners. The polymorphic forms of [Hg(L1)(ClO4)2] characterized (3 in P1[combining macron] and 4 in P21/c) had a mix of monodentate, anisobidentate and bidentate perchlorates, providing the first examples of a tricapped trigonal prismatic Hg(ii) coordination geometry, as well as additional examples of a rare square antiprismatic Hg(ii) coordination geometry. Solution state (1)H NMR characterization of the Group 12 complexes in CD3CN indicated intramolecular reorganization remained rapid under conditions where intermolecular M-L1 exchange was slow on the chemical shift time scale for Zn(ii) and on the J(M(1)H) time scale for Cd(ii) and Hg(ii). Solution studies with more than one equivalent of ligand also suggested that a complex with a 1 : 2 ratio of M : L1 contributed significantly to solution equilibria with Hg(ii) but not the other metal ions. The behavior of related linear pentadentate ligands with Group 12 perchlorate salts is discussed.

The synthesis of a new endohedral ten-vertex Zintl ion cluster, [Fe@Sn10](3-), isoelectronic with [Fe@Ge10](3-), is reported. In an attempt to place this new cluster within the context of the known structural chemistry of the M@E10 family (M = transition metal, E = main group element), we have carried out a detailed electronic structure analysis of the different structural types: viz bicapped square antiprismatic ([Ni@Pb10](2-), [Zn@In10](8-)), tetra-capped trigonal prismatic ([Ni@In10](10-)) and the remarkable pentagonal prismatic [Fe@Ge10](3-) and [Co@Ge10](3-). We establish that the structural trends can be interpreted in terms of a continuum of effective electron counts at the E10 cage, ranging from electron deficient (4n + 2) in [Fe@Ge10](3-). The effective electron count differs from the total valence electron count in that it factors in the increasingly active role of the metal d electrons towards the left of the transition series. The preference for a pentagonal prismatic geometry in [Fe@Ge10](3-) emerges as a natural consequence of backbonding to the cage from four orthogonal 3d orbitals of the low-valent metal ion. Our calculations suggest that the new [Fe@Sn10](3-) cluster should also exhibit structural consequences of backbonding from the metal to the cage, albeit to a less extreme degree than in its Ge analogue. The global minimum lies on a very flat surface connecting D4d, C2v and C3v-symmetric minima, suggesting a very plastic structure that may be easily deformed by the surrounding crystal environment. If so, then this provides a new and quite distinct structural type for the M@E10 family.