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A new set of lighter lanthanide complexes having general formula (GunH)3[Ln(tdp)3]·3H2O (Ln = La, Pr, Nd, and Sm) derived from thiodipropionic acid (H2tdpa) and guanidine carbonate [Gun.(H2CO3)1/2] were synthesized by template method in aqueous medium. These complexes were characterized by various physico-chemical techniques, such as elemental analysis, molar conductance, FT-IR, UV–Vis, TG–DTA (air and nitrogen atmosphere), and PXRD studies. In this manuscript, for first time, the sulfur content of the acid in the complexes has been estimated by simple volumetric analysis. From the thermal analysis, all of the complexes are assisted with water molecules, which decompose endothermic followed by exothermic decomposition to yield Ln2(SO4)3 as the end residue. All the complexes are stabilized by nine coordinated monocapped square antiprismatic or tricapped trigonal prismatic geometry and found to be monomeric in compositions, which is proposed by various physico-chemical techniques. The isomorphism of these complexes is revealed by PXRD technique. Furthermore, the luminescence properties of free acid and the synthesized complexes were studied at room temperature in solid state.

Photophysical properties of europium (Eu(III)) complexes are affected by ligand-to-metal charge transfer (LMCT) states. Two luminescent Eu(III) complexes with three tetramethylheptadionates (tmh) and pyridine (py), [Eu(tmh)(3)(py)(1)] (seven-coordinated monocapped-octahedral structure) and [Eu(tmh)(3)(py)(2)] (eight-coordinated square antiprismatic structure), were synthesized for geometrical-induced LMCT level control. Distances between Eu(III) and oxygen atoms of tmh ligands were estimated using single-crystal X-ray analyses. The contribution percentages of pi-4f mixing in HOMO and LUMO at the optimized structure in the ground state were calculated using DFT (LC-BLYP). The Eu-O distances and their pi-4f mixed orbitals affect the energy level of LMCT states in Eu(III) complexes. The LMCT energy level of an eight-coordinated Eu(III) complex was higher than that of a seven-coordinated Eu(III) complex. The energy transfer processes between LMCT and Eu(III) ion were investigated using temperature-dependent and time-resolved emission lifetime measurements of D-5(0) -> F-7(J) transitions of Eu(III) ions. In this study, the LMCT-dependent energy transfer processes of seven- and eight-coordinated Eu(III) complexes are demonstrated for the first time.

The methylation of p-tert-butylcalix[4]arene in the distal 1,3-phenolic sites provides the ligand H2L = {p-tert-butylcalix[4](OMe)2(OH)2arene} that enables construction of heteroleptic mononuclear lanthanide complexes. The reaction of (N(nBu)4)(acac) (Hacac = acetylacetone), MIIICl3 and H2L under Schlenk conditions results in the formation of a family of (N(nBu)4)[MIIIL(acac)2] complexes where M = Y (1), Gd (2), Tb (3) and Dy (4). The metal ions are eight-coordinate in distorted square-antiprismatic coordination geometries, resulting in slow relaxation of the magnetisation for the Tb derivative.

Reported herein are mutual rearrangements in the whole series of seven bicapped-square antiprismatic closo-C2B8H10 by means of high-quality computations that disprove the earlier postulated dsd (diamond-square-diamond) scheme for these isomerizations. The experimentally existing closo-1,2-C2B8H10 was able to be converted to 1,6-, and 1,10-isomers by pyrolysis, and the dsd (diamond-square-diamond) mechanism was offered as an explanation of these processes. However, these computations disprove the postulated dsd scheme for these isomerizations that take place in the ten-vertex closo series. Experimentally observed thermal rearrangements, both in the parent and substituted closo-1,2-C2B8H10, closo-1-CB9H10−, and closo-B10H102−, indirectly support these refined computations. All these processes are based on the new concept of the so-called Z-mechanism, being consistent with a transition state of a boat shape with an open hexagonal belt that results from the initial breakage of three bonds. Such bond breakings and the consequent bond formations bring to mind the shape of the letter Z. In effect, the pattern of multicenter bonding shifts from reactant through a transition state to product. The molecular rearrangements that are available experimentally favour either the axial or equatorial isomers, and this ratio depends on temperature and the type of cluster and its substitution.

A series of five mononuclear β-diketonate-Dy(iii) complexes, with formulas Dy(ntfa)3(Br-bpy) (1), Dy(ntfa)3(Br2-bpy) (2), Dy(ntfa)3(5,5-(CH3)2-bpy) (3), Dy(ntfa)3(4,4-((CH3)3)2-bpy) (4) and Dy(ntfa)3(4,4-(CH3)2-bpy) (5) (ntfa = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, Br-bpy = 5-bromo-2,2'-bipyridine, Br2-bpy = 4,4'-dibromo-2,2'-bipyridine, 5,5-(CH3)2-bpy = 5,5'-di-methyl-2,2'-bipyridine, 4,4-((CH3)3)2-bpy = 4,4'-di-tert-butyl-2,2'-bipyridine, and 4,4-(CH3)2-bpy = 4,4'-di-methyl-2,2'-bipyridine), have been prepared by altering the capping N-donor coligands. Dy(iii) ions in all complexes possess N2O6 octa-coordinated environments, displaying a distorted square antiprismatic D4d symmetry in complexes 1-4, as well as a triangular dodecahedron D2d symmetry in 5. Magnetic investigations evidence the SIM behavior in the five complexes with the energy barriers (Ueff) of 104.19 K (1), 122.93 K (2), 84.20 K (3), 64.16 K (4) and 80.23 K (5) under zero applied dc field. The potential QTM effects in the title complexes are successfully suppressed in the presence of the extra applied fields. The crystal field parameters and orientations of the magnetic easy axes were obtained from the simulation of the magnetic data and the electrostatic model calculation. The distinct electronic effects originating from the subtle changes of the substituents on the capping N-donor coligands induce varying coordination microenvironments and geometries on the Dy(iii) sites, further drastically impacting the overall magnetic properties of the title complexes. The disparities of the uniaxial anisotropy and the magnetic dynamics for 1-5 have been elucidated by ab initio calculations as well.

Two mononuclear Dy(III) compounds and one heteronuclear Dy(III)–K(I) compound, [Dy(tmpd)3(4,4′-dmpy)] (1), [KDy2(tmpd)8]·C5H6N (2) and [Dy(tmpd)3(dppz)] (3) (4,4′-dmpy = 4,4′-dimethyl-2,2′-bipyridyl, tmpd = 4,4,4-trifluoro-1-(4-methylphenyl)butane-1,3-dione, and dppz = dipyrido[3,2-a:2′,3′-c]phenazine), were synthesized by changing the organic bases and auxiliary ligands. The coordination environments of compounds 1 and 3 are different DyN2O6 configurations resulting from steric effects of different auxiliary ligands, while 2 has KF6O6 and DyO8 coordination environments because of the introduction of an organic base (CH3OK). The Dy(III) ions in compounds 1 and 2 have a triangular dodecahedral (D2d) configuration and square antiprismatic (D4d) configuration, respectively. Compound 3 contains two crystallographically equivalent Dy(III) ions of which the eight-coordinated geometries uniformly behave as distorted square antiprismatic (D4d) configurations. Compound 2 affords a novel Dy(III)–K(I) compound with unusually coordinated fluorine atoms of trifluoromethyl groups of β-diketone ligands. 2 is a centrosymmetric structure in which the central K(I) ion is located at the middle of two Dy(III) ions, resulting in an icosahedral (Ih) configuration. Magnetic investigations demonstrate that 1 and 3 display slow magnetic relaxation behaviors. The effective barriers are 94.91 K in 1 and 82.44 K in 3. The M versus H data exhibit weak butterfly-shaped hysteresis loops at 2 K for 1 and 3. The uniaxial magnetic anisotropies, magnetostructural correlations and relaxation mechanism were investigated both experimentally and theoretically. The experimental and theoretical studies indicate that compound 1 exhibits the best magnetic properties among compounds 1–3. The theoretical predictions of quantum tunneling of magnetization time and effective barriers are consistent with the corresponding experimental values. Our results indicate that the different organic bases and substituted groups of auxiliary ligands play an important role in synthetic processes, finally affording distinct structures and magnetic properties.

A new compound [Gd(H2O)4(HIA)2(NO3)](2NO3) (1; HIA is isonicotinic acid) is reported. The Gd3+ cation is coordinated by eight oxygen atoms and exhibit a square antiprismatic GdO8 geometry. A three-...

A new zero-dimensional cyanide-based coordination complex consisting of hexacyanocobaltate(III)-based building block and Tm(III) has been synthesized and characterized through single-crystal X-ray analysis, elemental analysis, and TGA analysis. The complex comprises of the cyano-bridged bimetallic assembly, {[Tm(DMF)2(CH3OH)2(H2O)2(μ-CN)Co(CN)5]}2 (1). The neutral complex consists of two TmIII centers coordinated with DMF, aqua, and methanol groups and bridged via cyanide to two different [Co(CN)6]3− moieties. Each TmIII has a coordination number of eight and a square antiprismatic geometry. The structure was further proved by thermogravimetric analysis which indicates the formation of complex 1. Brilliant luminescence property of the complex makes it a suitable material for medicinal applications.

Reaction of the 9,9-dimethylxanthene-bis(imine)-bis(catechol) ligand XbicH4 with half an equivalent of Zr(acac)4 affords the neutral tetracatecholate complex (XbicH2)2Zr, containing four iminium ions hydrogen bonded to the catecholates. The heteroleptic bis(catecholate)-tetraphenylporphyrin complex (TPP)Zr(XbicH2) is formed from reaction of (TPP)Zr(OAc)2 with XbicH4 in the presence of base. Both compounds adopt an eight-coordinate square antiprismatic geometry around the zirconium center. NMR spectra of (TPP)Zr(XbicH2) show that it is fluxional at room temperature, with homoleptic (XbicH2)2Zr showing fluxionality at higher temperatures. Calculations and kinetic isotope effect measurements suggest that the motions involve dissociation of a single catecholate oxygen and subsequent twisting of the seven-coordinate species. The compounds show reversible one-electron oxidations of each of the bound catecholates to bound semiquinones.

Six dimetallic lanthanide complexes, [Ln2(L')(acac)4] (1Dy-3Gd) (Ln = Dy (1Dy), Tb (2Tb) and Gd (3Gd)) and [Ln2(L')(tfac)4] (4Dy-6Gd) (Ln = Dy (4Dy), Tb (5Tb) and Gd (6Gd)) (H2L' = 1,9-dichloro-3,7,11,15-tetraaza-1,9(1,3)-dibenzenacyclohexadecaphane-2,10-diene-1,9-diol), have been synthesized by the reaction of lanthanide nitrates with the HL ligand in the presence of acetylacetonate (acac) (or trifluoroacetylacetonate (tfac) and triethylamine (HL = 4-chloro-2,6-bis(-((3-((3-(dimethylamino)propyl)amino)propyl)imino)methyl)phenol). Ln-Assisted modification of the Schiff base HL occurred and led to the formation of a new macrocyclic ligand (H2L'). X-ray crystallographic analysis revealed that the LnIII ions of complexes 1Dy-6Gd are all eight-coordinated in a square antiprismatic geometry with D4d local symmetry. Magnetic measurements of these complexes revealed that 1Dy and 4Dy show single-molecule magnet behaviour with energy barriers of 66.7 and 79.0 K, respectively, under a zero direct magnetic field. The orientations of the magnetic axes and crystal field parameters were obtained from theoretical calculations and an electrostatic model. The magneto-structural correlations of SMMs 1Dy and 4Dy are further discussed in detail.

Four new homodinuclear isostructural luminescent EuIII and TbIII complexes containing N,N-heterocyclic bases (DPQ/DPPZ) and tolfenamic acid (TFA) presented as [Ln2(DPQ/DPPZ)2(TFA)6], where LnIII = EuIII [DPQ (1), and DPPZ (2)] and TbIII [DPQ (3) and DPPZ (4)], were studied in this work. The planar DPQ/DPPZ ligands used are well-known intercalators and photosensitizers. Tolfenamic acid (TFA) used as an anthranilic acid derivative-based NSAID, provides the hard carboxylate-O-donor for hard LnIII Lewis acids, and can form a bridge between two LnIII ions. The SC-XRD studies on the dinuclear complexes revealed their isostructural nature in the solid state. This is due to the similarity of both LnIII ions, exhibiting identical ligand disposition in 3D and electronic interactions with the ligands. All the complexes possess Ci symmetry, making the coordination environment around each LnIII identical. The two LnIII ions in the dimeric structures are bridged by –COO− groups of the four TFA molecules in a μ-η1:η1 coordination mode. Additionally, one TFA is coordinated to each LnIII in an η2-chelating mode together with one bidentate N,N-donor DPQ/DPPZ ligand. Therefore, each EuIII/TbIII ion ultimately possesses an eight-coordinated {Ln2N2O6} square antiprismatic geometry. The luminescent complexes showed the characteristic (5DJ → 7FJ) f–f transitions in solution with a quantum yield in the range of 8–20%, and thus were utilized for cellular fluorescence imaging studies. The affinity of the complexes with biological targets such as DNA and serum albumin was studied. The cellular uptake and bioimaging potential of the luminescent compounds in MCF-7 and HeLa cancer cells were probed using confocal fluorescence imaging studies. The sufficient internalization of the LnIII-probes in the cells observed from the intrinsic luminescence from EuIII/TbIII demonstrated their non-selective cytosolic and nuclear localization. The complexes were photo-cytotoxic at 365 nm mediated by the ROS generated from the photo-excitation of the DPQ/DPPZ sensitizers.

A series of mononuclear DyIII compounds, [Dy(tmpd)3(4,4'-dmpy)] (1), [Dy(tffb)3(4,4'-dmpy)] (2), [Dy(tffb)3(5,5'-dmpy)] (3), and [Dy(tmpd)3(5,5'-dmpy)] (4) [tmpd = 4,4,4-trifluoro-1-(4-methoxyphenyl)-1,3-butanedione, tffb = 4,4,4-trifluoro-1-(4-fluorophenyl)-1,3-butanedione, 4,4'-dmpy = 4,4'-dimethyl-2,2'-bipyridyl, and 5,5'-dmpy = 5,5'-dimethyl-2,2'-bipyridyl], have been synthesized by modifying β-diketonate ligands and capping N-donor co-ligands. DyIII ions in 1-4 possess N2O6 octacoordinated environments. Compounds 1 and 2 exhibit distorted trigonal dodecahedron configurations, while 3 and 4 display distorted square antiprismatic configurations. Systematic investigations of the alternating current measurements indicate the different magnetic relaxation dynamics with energy barriers (Ueff) of 66 K (1, 45 cm-1), 189 K, (2, 131 cm-1), 115 K (3, 79 cm-1), and 205 K (4, 142 cm-1). To deeply understand their different magnetic behaviors, the magnetic anisotropies of 1-4 were studied by ab initio calculations. From ab initio calculations, the energies of the first excited state (KD1) are consistent with the experimental Ueff under zero direct current field. Compound 4 presents the largest Ueff because of the smallest gX,Y and μQTM as well as the most strong axial crystal field parameters (CFPs) among compounds 1-4. The M versus H data exhibit butterfly-shaped hysteresis loops at 2 K for 1-4. The different coordination geometries, the magnetic dynamics, the electrostatic repulsion, and CFPs result from the different substituent effects of ligands, including the electronic effect, the steric effect, and the positions of substituted groups.

Two novel lanthanide complexes, [Ln2(3,4-DClBA)6(5,5′-DM-2,2′-bipy)2(C2H5OH)(H2O)] (Ln = Gd(1), Tb(2)); 3,4-DClBA: 3,4-dichlorobenzoate; 5,5′-DM-2,2′-bipy: 5,5′-dimethyl-2,2′-bipyridine) have been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, thermal analysis and single X-ray diffraction techniques. The binuclear complexes 1–2 are isomorphous and crystallize in the triclinic crystal system and P 1 ¯ space group, and each metal center is eight-coordinated with distorted square antiprismatic molecular geometry. The structure of this type of complex is unique in that the solvent ethanol molecule participates in the coordination. Complexes 1–2 are stitched together via π–π stacking interactions and hydrogen bonding interactions to form the 1D, 2D supramolecular structures. The thermal decomposition mechanisms of two complexes were obtained by TG-DSC/FTIR techniques. The molar heat capacities of the complexes 1 and 2 are measured by a DSC instrument over the temperature range from 255.15 to 323.15 K and thermodynamic functions were calculated by fitted polynomial and thermodynamic equations. The luminescence studies demonstrate that complex 2 exhibits the characteristic emission of Tb3+ ion (5D4 → 7F6-3).

In this work we report the synthesis, structure and magnetic properties of two lanthanoid based coordination polymers (CP) and two dimers prepared with two derivatives of the 2,5-dihydroxy-1,4-benzoquinone (C6O4X2)2− as ligands. Using the bromanilato ligand: (C6O4Br2)2− we have prepared the CP [Eu1.96Dy0.04(C6O4Br2)3(DMSO)6]·2DMSO (1) (DMSO = dimethylsulfoxide) and with the chlorocyananilato ligand: (C6O4(CN)Cl)2−) we have prepared one CP formulated as [Eu1.96Dy0.04(C6O4(CN)Cl)3(DMSO)6] (2) and two isostructural dimers: [Eu1.96Dy0.04(C6O4(CN)Cl)3(H2O)10]·6H2O (3) and [Eu2(C6O4(CN)Cl)3(H2O)10]·6H2O (4). Compounds 1, 2 and 3 are Eu(III) compounds doped with 2.0 % of Dy(III), whereas compound 4 is a pure phase of Eu(III). The X-ray structure of these CPs shows that compounds 1 and 2 present neutral (6,3)-2D networks with rectangular cavities in 1 and very distorted hexagonal cavities in 2, while 3 and 4 are isostructural and present a dimeric structure where the Ln(III) ions are connected by a bis-bidentate chlorocyananilato ligand. Each metal completes its nonacoordination environment with a terminal bidentate chlorocyananilato ligand and five water molecules in a slightly distorted capped square antiprismatic geometry. In addition, these coordination complexes have very interesting magnetic properties. Compounds 1 and 3 behave as single-molecule magnets (SMM) with energy barriers of 40.9 and 25.3 K, respectively. In contrast, compound 2 does not present any SMM behaviour.

The effect of the ring size of the central cavity of a triaza macrocycle on coordination, bonding and properties is described through synthesis, characterization and detailed DFT studies. For this, two new Eu3+ and Tb3+ neutral complexes based on new 12N3 macrocyclic chelator bearing three 8-hydroxyquinoline pendants, [Ln(12N3Me5Ox)(H2O)n].xH2O (Ln = Eu3+ and Tb3+; 12N3Me5Ox = 1,5,9-tris-{(5-methylene-8-hydroxyquinoline)-1,5,9-triazacyclononane} (x = 4 for Eu and x = 5.3 for Tb; n = 2, 3) were synthesized and characterized by elemental analysis, FT-IR, FT-NMR, ESI-mass spectrometry, molar conductance and thermal analysis data. The spectral and analytical data reveal that both the complexes have different coordination number and geometry as compared to its lower homologue. The europium complex is eight coordinate with stoichiometry [Eu(12N3Me5Ox)(H2O)2].4H2O with twist square antiprismatic geometry while [Tb(12N3Me5Ox)(H2O)3].5.3H2O has nine coordination with distorted mono-capped square antiprismatic geometry. The FTIR and TGA analyses confirmed the presence of coordinated waters. The molecular modeling studies suggest that the metal ion can be easily encapsulated in the central cavity of the ligand. The geometries of the complexes are distorted due to parallel π−π and parallel-displaced π−π stacking arrangement between three pendants of 8HQ with inter planner distance are 3.318 and 3.821 A. The 1HNMR spectra of Eu3+ complex spectra were much sharper than that of Tb3+ complex. The photoluminescence spectra showed different behaviour in solid as compared to solution state. In the solid state, and at 77 K, the complexes showed characteristic lanthanide emission in addition to the ligand emission peaks. However, in solution, the lanthanide-centred emissions of the complexes were overlapped with the ligand emissions. A weak antenna effect was observed only in the powder form of the complexes. The vibrational data calculated from the DFT [GGA (B3LY-D3)] optimized structures showed good agreement with the experimental results. The excitation and emission behaviour of the ligand and the complexes were established by molecular orbital analysis of the ground state as well as on the excited state optimized geometry at DFT level. The nature of bonding between the lanthanide ions and the 12N3Me5Ox3−, interpreted by means of the natural bond orbital (NBO) and Morokuma Ziegler energy decomposition analysis (ETS-NOCV) scheme, suggest that the Ln-L bonds are more electrostatic (∼73%) than covalent (∼27%). The covalent character of the complexes increases in the order Tb > Eu. The Slater Condon parameters and spin-orbital coupling constants were calculated from LF-DFT (ligand field density functional theory) calculation. The theoretical Nephelauxetic parameter was also compared with experimental data.

Single crystals of Ln2Fe4- xCo xSb5- yBi y (Ln = La, Ce; 0 ≤ x < 0.5; 0 ≤ y ≤ 0.2) were grown using Bi flux and self-flux methods. The compounds adopt the La2Fe4Sb5 structure type with tetragonal space group I4/ mmm. The La2Fe4Sb5 structure type is comprised of rare earth atoms capping square Sb nets in a square antiprismatic fashion and two transition-metal networks forming a PbO-type layer with Sb and transition-metal isosceles triangles. Substituting Co into the transition-metal sublattice results in a decrease in the transition temperature and reduced frustration, indicative of a transition from localized to itinerant behavior. In this manuscript, we demonstrated that Bi can be used as an alternate flux to grow single crystals of antimonides. Even with the incorporation of Bi into the Sb square net, the magnetic properties are not significantly affected. In addition, we have shown that the incorporation of Co into the Fe triangular sublattice leads to an itinerant magnetic system.

Lanthanide coordination polymers (CPs) have attracted great interest for the development of new functional materials since they possess great structural complexity and a plethora of magneto-optical properties. Hence, herein, we studied the structural, topological, magnetic and optical properties of eight lanthanide CPs based on the very simple ligand glutaric acid (H2Glu):{[Ln(Glu)1.5(H2O)]·xH2O}n; (1), (2), (3) and (4), {[Ln2(Glu)3(DMF)(H2O)]·H2O}n; (5) and (6) and [Ln2(Glu)3(H2O)4]n (7) and (8) [Ln = Tb (1), Sm (2), Eu (3), Gd (4), Dy (5), Pr (6), Eu (7) and Gd (8); Glu = glutarate dianion, DMF = dimethylformamide; x = 2 for CPs 1, 2 and 4 and x = 0 for CP 3]. From a structural point of view, four different coordination modes were noted for the glutarate linker, specifically, (μ2-κ4, η2:η2), (μ3-κ5, η1:η2:η2), (μ4-κ6, η1:η2:η1:η2) and (μ4-κ5, η1:η1:η1:η2). The classification of the geometries of the coordination spheres showed that all the CPs feature muffin geometry with the exception of Dy2, Pr1 and Gd2 in CPs 5, 6 and 8, respectively, which are best described by the spherical monocapped square antiprismatic geometry. The topological simplification and classification of the coordination nets revealed that the topological types are strongly dependent on the metal-to-ion ratio in the resulting CP. The tcs topological type was observed in 1–4, which to date has predominantly appeared in CPs possessing two different ligands. This observation was ascribed to the high coordination number of the metal node based on the analysis of literature precedents. CPs 5 and 6 featured a four-nodal 3,3,3,9-connected net with the {411.616.89}{42.6}{43}{43} point symbol, which is unknown to date. The magnetic studies identified the presence of a strong magnetocaloric effect in the gadolinium CP 8. The value of the volume-normalized entropy parameter −ΔSmaxm was 62.4 mJ cm−3 K−1 at 2 K and ΔH = 7 T. The magnetocaloric effect was much larger than that for most reported Gd3+-based coordination compounds, and it was ascribed to the high magnetic density of the CP. For dysprosium CP 5, the presence of a slow magnetic relaxation process was detected based on the analysis of the frequency-dependent studies. CPs 1 (Tb3+), 2 (Sm3+), 3 and 7 (Eu3+) displayed characteristic f–f photoluminescence in the visible spectral region. Finally, DFT calculations were performed to analyze the hydrogen bonding interactions between the coordinated and non-coordinated water molecules and glutarate-based metallomacrocycles and to quantify the influence of metal coordination on the strength of the hydrogen bonds.

The unsolvated Cu(II) complex with bis(pentafluorobenzoyl)methanide ligand (L, C6F5COCHCOC6F5−) is prepared and crystallized as [CuL2] (1) using gas phase sublimation-deposition at 150 °C. The X-ray crystallographic characterization confirmed the centrosymmetric mononuclear structure of 1 with a square planar geometry around Cu(II) (Cu–Oav 1.9149(8) A). The reaction of 1 with sodium hexafluoroacetylacetonate [Na(hfac)] in a solvent-free environment afforded [Na2Cu2L4(hfac)2] (2), the first heterometallic Na–Cu β-diketonate characterized by single-crystal X-ray diffraction. In the centrosymmetric tetranuclear structure of 2, a dimeric [Na(hfac)]2 unit is sandwiched between two CuL2 units. The L-ligands function as chelating-bridging between Cu and Na through one of their O-atoms. The hfac ligands are chelating-bridging between Cu and Na and between Na(1) and Na(1A) through both O-atoms. In addition to the five primary Na–O interactions (av. 2.4109(17) A), three secondary Na–F contacts (av. 2.6006(15) A) contribute to the overall distorted square antiprismatic coordination environment for Na. The geometry of Cu is square pyramidal with Cu–O(L) distances averaging at 1.922(14) A and Cu–O(hfac) of 2.3021(15) A. Thermal decomposition of 2 yields a mixture of NaCuF3, Na2CuF4 and NaF, when conducted at 230 °C in argon at ambient pressure.

Four new hetero-pentanuclear 3d–4f complexes [Zn4(L)2La(NO3)2(OEt)(H2O)] (1), [Zn4(L)2Ce(NO3)2(OMe)(MeOH)] (2), [Zn4(L)2Pr(NO3)2(OEt)(EtOH)] (3) and [Zn4(L)2Nd(NO3)2(OMe)(MeOH)] (4) were synthesized by the reactions of a newly synthesized octadentate bis(salamo)-based tetraoxime ligand (H4L) with Zn(OAc)2·2H2O and Ln(NO3)3·6H2O (Ln = La, Ce, Pr and Nd), respectively, and characterized via elemental analyses, FT-IR, UV-Vis spectroscopy and single crystal X-ray crystallography. The X-ray crystallographic investigation revealed that all ZnII ions were located in N2O3 coordination spheres, and possessed a trigonal bipyramid coordination environment. The LnIII ion lay in an O8 coordination sphere, and adopted a distorted square antiprismatic coordination environment. Furthermore, supramolecular interactions and fluorescence properties were investigated.

The preparation and photoluminescent properties of the new [Eu(FOD)3(2-Pyr)2] complex (FOD = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octadionate; 2-Pyr = 2-pyrrolidone) are reported. The obtained complex was characterized by elemental analysis, complexometric titration using EDTA, infrared spectroscopy, and single-crystal X-ray diffraction studies. The coordination polyhedron of the complex is described as a distorted square antiprismatic with both 2-Pyr monodentate ligands coordinated to Eu(III) via the oxygen atoms, in neutral form, while the three FOD molecules are coordinated in the anionic form. Structural modeling at the PBE1PBE/SVP/MWB52 level of theory provided a geometry in excellent agreement with the one obtained experimentally. Spectroscopy properties such as intensity parameters (Ω2 and Ω4), radiative emission rate (Arad), and chemical partition of Arad for [Eu(FOD)3(2-Pyr)2] and [Eu(FOD)3(H2O)2] were calculated by using the QDC model with help of the semiempirical wavefunctions. The modeling of the ligand-to-metal energy transfer for both complexes was performed, allowing to obtain the theoretical emission quantum yield and to characterize the most relevant molecular orbitals involved.

EuIII, TbIII, GdIII and YbIII complexes of the nonadentate bispidine derivative L2 (bispidine=3,7‐diazabicyclo[3.3.1]nonane) were successfully synthesized and their emission properties studied. The X‐ray crystallography reveals full encapsulation by the nonadentate ligand L2 that enforces to all LnIII cations a common highly symmetrical capped square antiprismatic (CSAPR) coordination geometry (pseudo C4v symmetry). The well‐resolved identical emission spectra in solid state and in solution confirm equal structures in both media. As therefore expected, this results in long‐lived excited states and high emission quantum yields ([EuIIIL2]+, H2O, 298 K, τ=1.51 ms, ϕ=0.35; [TbIIIL2]+, H2O, 298 K, τ=1.95 ms, ϕ=0.68). Together with the very high kinetic and thermodynamic stabilities, these complexes are a possible basis for interesting biological probes., EuIII, TbIII, GdIII and YbIII complexes of a nonadentate bispidine derivative were successfully synthesized and their emission properties studied. The X‐ray crystallography reveals full encapsulation by the nonadentate ligand, and the identical emission spectra in the solid state and in solution confirm equal structures in both media. As therefore expected, this results in long‐lived excited states and high emission quantum yields, making these complexes a possible basis for interesting biological probes.

Bis(diphenylphosphino)methane dioxide (dppmO2) forms eight-coordinate cations [M(dppmO2)4]Cl3 (M = La, Ce, Pr, Nd, Sm, Eu, Gd) on reaction in a 4:1 molar ratio with the appropriate LnCl3 in ethanol. Similar reaction in a 3:1 ratio produced seven-coordinate [M(dppmO2)3Cl]Cl2 (M = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb), whilst LuCl3 alone produced six-coordinate [Lu(dppmO2)2Cl2]Cl. The complexes have been characterised by IR, 1H and 31P{1H}-NMR spectroscopy. X-ray structures show that [M(dppmO2)4]Cl3 (M = Ce, Sm, Gd) contain square antiprismatic cations, whilst [M(dppmO2)3Cl]Cl2 (M = Yb, Dy, Lu) have distorted pentagonal bipyramidal structures with apical Cl. The [Lu(dppmO2)2Cl2]Cl has a cis octahedral cation. The structure of [Yb(dppmO2)3(H2O)]Cl3&middot, dppmO2 is also reported. The change in coordination numbers and geometry along the series is driven by the decreasing lanthanide cation radii, but the chloride counter anions also play a role.

A series of five neutral mononuclear lanthanide complexes [Ln(HL)(L)] (Ln = Dy3+, Ho3+ Er3+ and Tb3+) with rigid pentadentate N3O2-type Schiff base ligands, H2LH (1-Dy, 3-Ho, 4-Er and 6-Tb complexes) or H2LOCH3, (2-Dy complex) has been synthesized by reaction of two equivalents of 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))dibenzohydrazine (H2LH, [H2DAPBH]) or 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))di-4-methoxybenzohydrazine (H2LOCH3, [H2DAPMBH]) with common lanthanide salts. The terbium complex [Tb(LH)(NO3)(H2O)2](DME)2 (5-Tb) with one ligand H2LH was also obtained and characterized. Single crystal X-ray analysis shows that complexes 1–4 have the composition {[Ln3+(HL)-(L)2-] solv} and similar molecular structures. In all the compounds, the central Ln3+ ion is chelated by two interlocked pentadentate ligands resulting in the coordination number of ten. Each lanthanide ion is coordinated by six nitrogen atoms and four oxygen atoms of the two N3O2 chelating groups forming together a distorted bicapped square antiprismatic polyhedron N6O4 with two capping pyridyl N atoms in the apical positions. The ac magnetic measurements reveal field-induced single-molecule magnet (SMM) behavior of the two dysprosium complexes (with barriers of Ueff = 29 K at 800 Oe in 1-Dy and Ueff = 70 K at 300 Oe in 2-Dy) and erbium complex (Ueff = 87 K at 1500 Oe in 4-Er); complex 3-Ho with a non-Kramers Ho3+ ion is SMM-silent. Although 2-Dy differs from 1-Dy only by a distant methoxy-group in the phenyl ring of the ligand, their dynamic magnetic properties are markedly different. This feature can be due to the difference in long-range contributions (beyond the first coordination sphere) to the crystal-field (CF) potential of 4f electrons of Dy3+ ion that affects magnetic characteristics of the ground and excited CF states. Magnetic behavior and the electronic structure of Ln3+ ions of 1–4 complexes are analyzed in terms of CF calculations.

The synthesis, structures, and characterization of two new families of trivalent lanthanide perrhenate complexes, [Ln(ReO4)(H2O)4Cl]Cl·H2O (Ln = La – Nd) (1) and [Ln(ReO4)3(H2O)2] (Ln = Tb, Ho, Er) (2), along with the expansion of a third known family, [Ln(ReO4)3(H2O)4] (Ln = Tm, Lu, Y) (3), is presented. Complex 1 is a purely inorganic member of a rare class of compounds known as cationic materials. Single crystal X-ray diffraction analysis reveals that 1 crystallizes in the P21/m space group and is comprised of two-dimensional (2D) sheets constructed from LnO4(H2O)4Cl monocapped square antiprismatic (CN = 9) lanthanide cations, 2 crystallizes in the C2 space group and is a three-dimensional (3D) structure constructed from two unique LnO6(H2O)2 square antiprismatic (CN = 8) lanthanide cations, and 3 crystallizes in the P21/n space group and is comprised of one-dimensional chains constructed from LnO4(H2O)4 square antiprismatic (CN = 8) lanthanide cations. This work provides a comprehensive study on essentially the entire lanthanide series (sans Pm) and its complexation with perrhenate at room temperature. The structural features of these complexes exhibit properties influenced by contracting ionic radii and increasing hardness upon traversing the lanthanide series.

A series of new dimethyl-sulfoxide-containing pertechnetates and perrhenates of tetravalent U, Np, and Pu were synthesized and structurally characterized by the X-ray diffractometry. In all the synthesized compounds, the actinide atoms were coordinated by eight DMSO molecules with or without an extra XO4- anion in the coordination sphere. This resulted in the square antiprismatic or capped square antiprismatic coordination of An atoms. Three or four XO4- anions play the role of outer-sphere anions. The electron and IR spectra of the compounds correlated with their crystal structure.

Pseudocontact shifts (PCS) generated by lanthanide chelating tags yield valuable restraints for investigating protein structures, dynamics and interactions in solution. In this work, dysprosium-, thulium- and terbium-complexes of eight-fold methylated 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid tags [DOTA-M8-(4R4S)-SSPy] are presented that induce large pseudocontact shifts up to 5.5 ppm and adopt exclusively the square antiprismatic conformation. This is in contrast to our earlier findings on complexes of the stereoisomeric DOTA-M8-(8S)-SSPy, where significant amounts of the twisted square antiprismatic conformer for the Dy tag were observed. The Dy-, Tm-, Tb- and Lu-complexes of DOTA-M8-(4R4S)-SSPy were conjugated to ubiquitin S57C and selectively 15N leucine labeled human carbonic anhydrase II S50C, resulting in only one set of signals. Furthermore, we investigated the conformation of the thulium- and dysprosium-complexes in vacuo and with implicit water solvent using density functional theory calculations. The calculated energy differences between the two different conformations (7.0–50.5 kJ/mol) and experimental evidence from the corresponding ytterbium- and yttrium-complexes clearly suggest a SAP [Λ(δδδδ)] geometry for the complexes presented in this study. The lanthanide chelating tag studied in this work offer insights into the solution structure of proteins by inducing strong pseudocontact shifts, show different tensor properties compared to its predecessor, enables a convenient assignment procedure, is accessed by a more economic synthesis than its predecessor and constitutes a highly promising starting point for further developments of lanthanide chelating tags.

Five dinuclear trivalent lanthanide complexes, [Ln(3-MOBA)3(5,5′-DM-2,2′-bipy)]2 (Ln = Er(1), Ho(2), Eu(3), Pr(4), Nd(5); 3-MOBA = 3-methoxybenzoate; 5,5′-DM-2,2′-bipy = 5,5′-dimethyl-2,2′-bipyridine) have been successfully synthesized via conventional solution method at room temperature and structurally characterized by single crystal and powder X-ray diffraction. The molecular structures of complexes 1–5 are very novel-innovative. Complexes 1 and 2 were isomorphic, and the complex 1 was obtained with the coordination number of eight to form a distorted square-antiprism coordination geometry, while complexes 3–5 were nine-coordinated with a distorted monocapped square antiprismatic coordination geometry, but they can be all assembled into the same 1D, 2D supramolecular structure, which has rarely been reported previously. Over the temperature range of 300–1200 K, the thermal decomposition mechanism of complexes 1–5 were discussed by the technology of TG/DSC-FTIR. The luminescence spectra of complex 3 displayed the characteristic emission of Eu3+ ion (5D0 → 7F0-4), and it’s CIE coordinate was also calculated as (0.647, 0.341). In addition, the luminescence lifetime and intrinsic luminescence quantum yield were also investigated. Beyond that, the magnetic properties of complexes 1–2 were studied in detail.

In this paper, we report the preparation of terbium(Tb+3) complex 2 (Diaqua-tris(nitrato)-(2(pyridine-2,6-diyl(methyleneoxy))benzaldehyde)terbium(III)) by the mechanochemical route in good yields, which demonstrated to be superior to conventional method in terms of simplicity, reaction time, cost and reproducibility. Complex 2 and its free ligand 1 (2,6-bis[2-formylphenoxymethyl]pyridine) were characterized by UV–Vis and FT-IR spectroscopy, and mass spectrometry. In addition, the complex was structurally characterized by Single-crystal XRD, and thermal analysis. The X-ray structure of complex demonstrates that terbium atom adopts a monocapped square antiprismatic geometry and cocrystallizes with one molecule of ligand in the asymmetric unit. Likewise, the effect of pH on the complex and its ligand revealed that fluorescent intensity is increased under alkaline conditions. In a preliminary study on selected heavy metals, terbium complex showed a good sensitive towards Cu+2 ions at low concentrations with the decrease of emission response.

A study of neptunium (Np) chemistry in the complex oxo-selenium system has been performed. Hereby, two sets of precipitation experiments were conducted, investigating the influence of the initial oxidation state of selenium using SeIVO2 and H2SeVIO4 with NpV in alkali nitrate solution, keeping the ratio of Np/Se constant. Surprising results were observed. Five novel neptunium and selenium bearing compounds have been obtained by slow evaporation from aqueous solution. The novel NpIV phase K4-x[Np(SeO3)4-x(HSeO3)x]·(H2O)1.5 (1) crystallizes in green-colored, plate-shaped crystals and was obtained by adding SeO2 and ANO3 to a NpV stock solution. Single-crystal X-ray diffraction reveals one-dimensional chain structures composed of square antiprismatic NpO8 polyhedra linked via four trigonal pyramidal SeO3 and HSeO3 units. Raman spectral analysis supports the presence of both selenite and hydroselenite due to the presence of corresponding modes within the spectra. The addition of selenic acid to a NpV stock so...

Using metal organic precursors in materials synthesis remains a challenge due to their high moisture susceptibility. In this work, we describe a facile methodology for the synthesis of Gd2O3-based contrast agents from two new gadolinium-based complexes. [Gd(PyTFP)4] (PyH) 1 (PyTFP = C8H5NOF3, Py = C5H5N) and [Gd(DMOTFP)3Py] 2 (DMOTFP = C8H7NO2F3) were synthesized via a classical ligand exchange reaction of [Gd{N(SiMe3)2}3] under inert conditions. As a result, X-ray diffraction analysis revealed a distorted square antiprismatic coordination and an augmented triangular prismatic arrangement of ligands around gadolinium atoms in 1 and 2, respectively. It also showed that 1 is an anionic complex of formula [Gd(PyTFP)4](PyH), while a neutral tris-compound, [Gd(DMOTFP)3Py], was obtained as a pyridine adduct in 2. Fast and reproducible microwave-assisted decomposition of 1 and 2 provided homogeneous Gd(OH)3 nanorods at mild temperature without using any surfactant or capping reagent. As-synthesized nanorods were...

The use of 2-naphthalenesulfonate (NAS) ligand in lanthanide chemistry afforded a family of isostructural mononuclear lanthanide complexes with the formula [Ln(NAS)2(H2O)6](NAS)·3H2O [Ln = Tb (1), Dy (2), Er (3), Yb (4)]. Crystallographic studies determined a square antiprismatic geometry (D4d) for the Ln centre and crystallization in an unprecedented chiral space group. The latter was further confirmed by the observation of Cotton effects in single crystal circular dichroism (CD) spectra. Static and dynamic magnetic measurements identified weak intermolecular dipolar interactions in 2, and such effects can be waived by dilution, which was noted by the detection of zero-field single molecule magnet (SMM) behaviour and hysteresis loop in a magnetically diluted sample (5). Compounds 2-4 exhibit SMM behaviours with energy barriers of 53, 32, and 45 K, respectively. To the best of our knowledge, these complexes are the first examples of pure 4f sulfonate-based SMMs.

Two linear-shaped heterometallic trinuclear {ZnII2DyIII} clusters were prepared with a compartmental Schiff-base ligand and carboxylate as the co-ligand. The central DyIII ion is sandwiched by two [ZnHhms(RCOO)2] (H2hms = (2-hydroxy-3-methoxybenzylidene)-semicarbazide) units to form a distorted square antiprismatic (SAP) geometry with D4d symmetry. The DyIII and ZnII ions are triply bridged by one unique monophenoxido/dicarboxylate group, where one of the carboxylates shows a severe angular distortion. The magnetic analysis revealed a field-dependent change with two relaxation processes in 1 and 2, which originated from the molecular magnetic center and dipolar–dipolar coupling. The dipole-induced slow relaxation disappeared upon magnetic-site dilution, while another faster relaxation appeared in the high frequency region associated with the different distortions of the antiprismatic sites for 1 and disordered structures for 2. Ab initio calculations revealed that two {ZnII2DyIII}-carboxylate complexes are axial in nature, but the remarkable quantum tunnelling of the magnetization exists in the ground state, which lowers the anisotropic barrier and prohibits zero-field single-molecule magnet behavior. The crystal field of the carboxylato ancillary ligands produces a competitive effect with the phenoxido bridging ligands on the magnetic anisotropy of the lanthanide ions, which greatly affects the electrostatic distribution of this type of {ZnII2DyIII} single-ion magnets (SIMs). The results offer a model for further investigating structural factors in the relaxation mechanism of SIM systems.

Two Dy(III) single-ion magnets, formulated as [Dy(Phen)(Cl-tcpb)3] (Cl-1) and [Dy(Phen)(CH3O-tmpd)3] (CH3O-2) were obtained through β-diketonate ligands (Cl-tcpb = 1-(4-chlorophenyl)-4,4,4-trifluoro-1,3-butanedione and CH3O-tmpd = 4,4,4-trifluoro-1-(4-methoxyphenyl)-1,3-butanedione) with different substituent groups (–Cl/–OCH3) and auxiliary ligand, 1,10-phenanthroline (Phen). The Dy(III) ions in Cl-1 and CH3O-2 are eight-coordinate, with an approximately square antiprismatic (SAP, D4d) and trigonal dodecahedron (D2d) N2O6 coordination environment, respectively, in the first coordination sphere. Under zero direct-current (dc) field, magnetic investigations demonstrate that both Cl-1 and CH3O-2 display dynamic magnetic relaxation of single-molecule magnet (SMM) behavior with different effective barriers (Ueff) of 105.4 cm−1 (151.1 K) for Cl-1 and 132.5 cm−1 (190.7 K) for CH3O-2, respectively. As noted, compound CH3O-2 possesses a higher effective barrier than Cl-1. From ab initio calculations, the energies of the first excited state (KD1) are indeed close to the experimental Ueff as 126.7 cm−1 vs. 105.4 cm−1 for Cl-1 and 152.8 cm−1 vs. 132.5 cm−1 for CH3O-2. The order of the calculated energies of KD1 is same as that of the experimental Ueff. The superior SIM properties of CH3O-2 could have originated from the larger axial electrostatic potential (ESP(ax)) felt by the central Dy(III) ion when compared with Cl-1. The larger ESP(ax) of CH3O-2 arises from synergic effects of the more negative charge and shorter Dy–O distances of the axial O atoms of the first sphere. These charges and distances could be influenced by functional groups outside the first sphere, e.g., –Cl and –OCH3.

Three new coordination polymers have been assembled by self-assembly of lanthanide(III) ions and succinic acid in dimethylformamide–water (DMF-H2O) mixed solvent having formulae; {[Ln(suc)1.5(H2O)2]•xH2O}n; (1), (2) and (3) [Where Ln = La (1), Pr (2) and Nd (3), suc = succinate dianion; x = 2 for CP 1, x = 1 for CP 2 and x = 4 for CP 3]. In all three coordination polymers (CPs) 1-3, the Ln(III) centres are ten coordinated with bicapped square antiprismatic geometry (SAPRS-10). Crystallographic analysis reveals that CPs 1-3 crystallize in triclinic system P¯1 space group. The linker succinic acid displays two different bonding modes: (μ2-κ4, η2:η2) and (μ4-κ6, η1:η2:η2:η1). All CPs 1-3 are isostructural and isomorphous. The two Ln centres in CPs 1-3 are bridged together through succinate anions via (μ4-κ6, η1:η2:η2:η1) mode forming dinuclear (Ln2O18) Secondary building unit (SBU) which are extended infinitely to generate one-dimensional chains. These 1D chains are further extended along the b-axis to form two-dimensional layered structures via (μ2-κ4, η2:η2) mode and finally three-dimensional network. In case of Nd, the quality of the crystal allows to locate a major number of lattice water molecules (x = 4) than in the other two complexes and, remarkably, the formation of water channels can be realized and studied. It has been analyzed using DFT calculations combined with the molecular electrostatic potential (MEP) surfaces, the quantum theory of “atoms-in-molecules” QTAIM and non–covalent interaction index (NCIplot) analyses.

Two new 2D coordination polymers, [Pb(NNO)2]n (1) and [Pb(NNO)(SCN)]n (2) (HNNO = nicotinic acid N-oxide), were synthesized and characterized by elemental analysis, FT-IR and 1H NMR spectroscopy, as well as single-crystal X-ray diffraction analysis. The thermal stability of the compounds was evaluated by thermogravimetric analysis. The compounds crystallize in the monoclinic space group P21/c. X-ray analysis of complexes revealed 2D coordination polymer containing lead atoms with PbO7 (1) and PbO4S (2) environments and hemidirected sphere. In addition to dative bonds around the lead atoms, there are Pb⋯X (X: O for 1 and N, O, S for 2) interactions to stabilize the complexes and form pseudo-capped square antiprismatic (1) and pseudo-bicapped trigonal prismatic (2) geometries. Two crystal structures are consisting of rectangular-shaped grids constructed with the NNO‾ linkers. These two-dimensional coordination polymers are further connected to form a 3D supramolecular networks by intermolecular interactions.

The structure of a mixed-ligand complex tris-(dipivaloylmethanato)(ethylendiamine)yttrium(III) [Y(en)(dpm)3] is studied at 150(2) K by single crystal XRD. The crystallographic data for C35H65N2O6Y are as follows: space group P21/c, a = 10.3771(3) A, b = 26.3566(8) A, c = 14.8412(4) A, β = 100.385(2)°, V = 3992.6(2) A3, Z = 4. The structure is molecular. The coordination environment of yttrium atoms is square antiprismatic; the Y–О distances are 2.2597(13)-2.3760(12) A and Y–N distances are 2.5381(16) A and 2.5499(17) A.

Two isostructural octanuclear {(LnIII4CoII4)(C8A)2} compounds (Ln = Dy, Er; H8C8A = p-tert-butylcalix[8]arene) were synthesized under solvothermal conditions for magnetic study. For comparison, an yttrium compound having a similar structure except some coordinated DEF molecules replaced by water molecules was obtained. These three compounds are featured with a sandwich-like motif in which the heterometallic {LnIII4Co4II} square antiprismatic cluster is sandwiched between two calix[8]arene molecules in double-cone conformation. Magnetic measurements revealed that the {DyIII4CoII4} compound exhibits single molecule magnet (SMM) behavior.

Two novel lanthanide complexes with the general formula [Ln(2-Br-5-MOBA) 3 (2,2′-DIPY)] 2 (Ln = Pr(1), Dy(2); 2-Br-5-MOBA = 2-bromine-5-methoxybenzoate; 2,2′-DIPY = 2,2′-bipyridine) have been successfully synthesized and characterized. The complexes 1 and 2 are isostructural and nine-coordinated with distorted monocapped square antiprismatic coordination geometry by the single-crystal X-ray diffraction analyses. Two complexes are all assembled into the 1D, 2D, 3D supramolecular structures by C H⋯O hydrogen bonding and π–π stacking interactions. The thermal decomposition mechanism for title complexes were obtained by TG/DSC-FTIR technology. The molar heat capacities of the complexes 1 and 2 are measured by a DSC instrument over the temperature range from 263.15 K to 365.15 K. On the basis of the fitted polynomial and thermodynamic equations, the smoothed values of heat capacities and thermodynamic functions ( H T - H 298.15K ), and ( S T - S 298.15K ) of the two complexes are calculated. In addition, the fluorescence spectra indicate that the complex 2 exhibits the characteristic emission of Dy(III) ion ( 4 F 9/2 → 6 H 13/2–15/2 ).

A new air and water stable divalent Europium squarate, [Eu(C4O4)(H2O)] (1), has been prepared and structurally characterized. 1 was synthesized by in situ reduction of a trivalent Europium salt using a Zinc amalgam and mild solvothermal heating. The resulting divalent Europium metal centers in 1 are both air and water stable. This demonstrates that this methodology does not require strict anaerobic conditions. A variation on the synthetic conditions used to prepare 1 (sans the Zinc amalgam) yielded two new series of trivalent lanthanide squarates, [Ln2(C4O4)2(C4O3OH)2(H2O)12] (Ln ​= ​La – Nd) (2) and [Ln2(C4O4)3(H2O)8] (Ln ​= ​Dy – Lu) (3), which have also been structurally and spectroscopically characterized. Single crystal X-ray diffraction analysis reveals that 1 crystallizes in the C2/m space group and is a 3D structure constructed from sheets of EuO7(H2O) polyhedra with an unusual triangular dodecahedral (CN ​= ​8) geometry, 2 crystallizes in the P 1 ¯ space group and is a 0D structure constructed from LnO3(H2O)6 monocapped square antiprismatic (CN ​= ​9) metal centers, and 3 crystallizes in the P21/n space group and is a 2D sheet structure constructed from LnO4(H2O)4 square antiprismatic (CN ​= ​8) metal centers. In all structures, the squarate ligands bind to the metal centers with varying, and sometimes uncommon, coordination modes and denticities. Herein, the synthesis, structure, and solid-state UV–vis–NIR spectroscopy of 1, 2, and 3 are presented.

Two lanthanide complexes [La(3,4-DMBA)3]n (1) and [Tb(3,4-DMBA)3(DIPY)2]2 (2) (where 3,4-DMBA = 3,4-dimethylbenzoate, DIPY = 2,2′-bipyridine) have been synthesized and then characterized. The single crystals of complexes 1 and 2 were obtained. Complex 1 adopts a distorted monocapped square antiprismatic molecular geometry, while complex 2 forms a distorted square antiprism. Complex 1 is stitched together by edge sharing through carboxylate ligands to form 1D chains along the b axis. The structure of complex 2 consists of 1D chains along the c axis by two kinds of π···π stacking interactions. Two complexes were characterized by elemental analysis, powder X-ray diffraction and IR spectra. The complex 2 shows typical green luminescence in the solid state. Thermal decomposition mechanisms of complexes were discussed by TG–DTG techniques. In the temperature range from 257.15 to 413.15 K, the molar heat capacities of the complexes were measured by DSC. The smoothed heat capacities and thermodynamic functions of complexes were calculated on the basis of fitted polynomial and thermodynamic equations.

Three novel ternary lanthanide complexes [Ln(2,5-DClBA)3(terpy)(H2O)] (Ln = Eu (1), Tb (2), Ho (3), 2,5-DClBA = 2,5-dichlorobenzoate, terpy = 2,2:6′,2″-terpyridine) have been successfully synthesized and characterized by single-crystal and powder X-ray diffraction. Complexes 1–3 are isostructural, and each metal center is nine-coordinated with distorted monocapped square antiprismatic coordination geometry. The mononuclear units are assembled into 1D, 2D, 3D supramolecular structures by the π–π stacking and halogen–halogen interactions. Thermal decomposition mechanisms of the title complexes were investigated by thermogravimetric analysis and further authenticated by TG/DSC-FTIR techniques. The solid-state fluorescent properties of complexes 1–2 were studied at room temperature, and characteristic emission was observed for all complexes. Complex 1 exhibits the strong red emission, while the complex 2 is green under UV light. Moreover, the antibacterial activities of the complexes against Candida albicans, Escherichia coli and Staphylococcus aureus were also evaluated.

Single crystals of Na3GaF6 were prepared via a mild hydrothermal method and the crystal structure was characterized by single crystal X-ray diffraction. Na3GaF6 crystallizes in the monoclinic space group P21/n with a = 5.4724(3) A, b = 5.6742(3) A, c = 7.8866(4) A, γ = 90.361(1)˚, V = 244.89(2) A3, and Z = 2. The compound exhibits a cryolite-type crystal structure consisting of corner-shared GaF6 and Na(1)O6 polyhedra. The Ga and Na(1) atoms are found in almost regular octahedra, whereas the Na(2) atom is observed in a highly distorted square antiprismatic coordination environment. The synthesis and crystal structure of the hexafluorogallate, Na3GaF6 is reported.

Four lanthanide complexes, [La2(2,4-DClBA)6(5,5′-DM-2,2′-bipy)2(H2O)2]·2C2H5OH (1) and [Ln(2,4-DClBA)3(5,5′-DM-2,2′-bipy)(C2H5OH)]2 (Ln = Pr(2), Sm(3), Gd(4); 2,4-DClBA = 2,4-dichlorobenzoate; 5,5′-DM-2,2′-bipy = 5,5′-dimethyl-2,2′-bipyridine), were synthesized and characterized via elemental analysis, infrared spectra and thermogravimetric analysis (TG). The crystal structures of 1 and 2–4 are different; Each La3+ is nine-coordinate adopting a distorted mono-capped square antiprism, while the Ln3+ ions of 2–4 are all eight-coordinate with a distorted square antiprismatic molecular geometry. There are subtle changes in the local coordination geometry of the lanthanide–5,5′-DM-2,2′-bipy complexes. Binuclear 1 complexes are stitched together via two kinds of hydrogen bonding interactions (OH⋯O and CH⋯O) to form 1-D chains along the y axis, while the units of 2–4 are stitched together via CH⋯O to form 1-D chains along the x axis. TG analysis revealed thermal decomposition processes and thermal stabil...

Two eight-coordinate Zr(IV) complexes of tetradentate Schiff base ligands, bis(3-ethoxysalicylidene)-4,5-dimethyl-1,2-phenylenediamine (H2L) and bis(3-ethoxysalicylidene)-2,2-dimethyl-1,3-propanediamine (H2L′), were prepared from Zr(acac)4 in refluxing methanol. The complexes were characterized by physico-chemical and spectroscopic methods. Also, their solid-state structures were determined by single-crystal X-ray diffraction. The crystal structure data showed a tetradentate mode of coordination for both Schiff bases, through N2O2 donor sets. The geometries of the complexes were dodecahedral and square antiprismatic for Zr(L)2 and Zr(L′)2, respectively. The complexes were screened in vitro against various microbes, revealing their antimicrobial activity.

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 novel lanthanide complexes, (EnH2)[NdIII(Egta)H2O]2 · 6H2O (I) and (EnH2)1.5[NdIII(Ttha)] · 5H2O (II), where En = ethylenediamine, H4Egta = ethyleneglycol-bis-(2-aminoethylether)-N,N,N′,N'-tetraacetic acid and H6Ttha = triethylenetetramine-N,N,N',N'',N''',N'''-hexaacetic acid, have been successfully synthesized through direct heating reflux and their molecular and crystal structures were determined by FT-IR spectroscopy, thermal analysis and single crystal X-ray diffraction (CIF files CCDC nos. 1436598 (I) and 1433221 (II)). X-ray diffraction reveals that I has a nine-coordinate mononuclear structure with pseudo-monocapped square antiprismatic conformation. Complex I crystallizes in a monoclinic system with P21/c space group; a = 13.0919(12), b = 12.6840(11), c = 16.9751(14) A, β = 122.069(3)° and V = 2388.7(4) A3. Complex II takes ten-coordinated structure with a distorted bicapped square antiprismaticprism belong to triclinic crystal system with P1 space group; a = 9.9376(10), b = 12.2178(12), c = 15.2671(16), β = 100.2480(10)° and V = 1609.5(3) A3. Each EnH2 2+ cation in I connects four adjacent [NdIII(Egta)H2O]– anions through hydrogen bonds. In II crystal cell, there are two types of cations, which form hydrogen bonds with the neighboring [NdIII(Ttha)]3– anions, leading to the formation of a 2D ladder-like layer structure. The results showed that the change of ligands can lead to change of the structure of the complexes, coordination numbers and coordination geometries. Thus, it can be concluded that the shape of ligands play a crucial role on the coordinate structure of complexes, coordination numbers and coordination geometries.

The reaction of ZrCl4 with oleum (65 % SO3) in the presence of Ag2SO4 at 250 °C yielded colorless single crystals of Zr(S2O7)2 [orthorhombic, Pccn, Z = 4, a = 709.08(6) pm, b = 1442.2(2) pm, c = 942.23(9) pm, V = 963.5(2) × 106 pm3]. Zr(S2O7)2 shows Zr4+ ions in an eightfold distorted square antiprismatic coordination of oxygen atoms belonging to four chelating disulfate units. Each S2O72– ion is connected to a further Zr4+ ion leading to chains according to 1∞[Zr(S2O7)4/2]. The same reaction at a temperature of 150 °C resulted in the formation of Ag4[Zr(S2O7)4] [monoclinic, C2/c, Z = 4, a = 1829.35(9) pm, b = 704.37(3) pm, c = 1999.1(1) pm, β = 117.844(2)°, V = 2277.6(2) × 106 pm3]. Ag4[Zr(S2O7)4] exhibits the unprecedented [Zr(S2O7)4]4– anion, in which the central Zr4+ cation is coordinated by four chelating disulfate units. Thus, in Ag4[Zr(S2O7)4] the 1∞[[Zr(S2O7)4/2] chains observed in Zr(S2O7)2 are formally cut into pieces by the implementation of Ag+ ions.

[Abstract] The solution dynamics of the Eu(III) complexes of H4dota (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracarboxylic acid) and H5do3ap (1,4,7,10-tetraazacyclododecane-4,7,10-tris(carboxymethyl)-1-methylphosphonic acid, bound in both monoprotonated and fully deprotonated forms) were investigated by using a combination of NMR measurements and DFT calculations. In solution, an equilibrium between the square antiprismatic (SAP) and twisted-square antiprismatic isomers (TSAP) of these complexes is present. These two isomers interconvert by rotation of the pendant arms or inversion of the cyclen chelate rings. 1D EXSY NMR spectra were used to determine these exchange rates with unprecedented accuracy. It was found that the two processes occur at different rates. Additional variable-temperature measurements allowed determination of the corresponding activation parameters for the two processes. DFT calculations were then used to obtain mechanistic information at the molecular level. The results show that the cyclen inversion pathway involves stepwise inversion of the four chelate rings formed upon metal ion coordination. However, the arm rotation process may operate through a synchronous rotation of the pendant arms or a stepwise mechanism depending on the system. A mixed cluster-continuum approach was required to improve the agreement between experimental and calculated activation parameters for the arm rotation process. The obtained results will aid the design of MRI contrast agents. Furthermore, the methodology developed in this work can be further applied for the investigation of other dynamic paramagnetic systems, e.g. peptides with Ln(III) probes or natively paramagnetic metalloproteins. Czech Science Foundation; 16-03156S Charles University; 1076016 Czech Republic. Ministry of Education; LTC 170607 Ministerio de Economía y Competitividad; CTQ2013-43243-P

Geometry and magnetic interaction modulations in a series of dinuclear dysprosium compounds, [Dy2Lz2(OAc)6]·2CH3OH (1), [Dy2Lz2(C6H5CO2)6]·2CH3CN (2), and [Dy2L2(SO3CF3)4THF4] (3) (Lz = 6-pyridin-2-yl-[1,3,5]triazine-2,4-diamine; L = N-(2,3-dimethylbut-3-en-2-yl)-N-hydroxynitrous amide; THF = tetrahydrofuran), can effectively tune the relaxation dynamics of magnetization. The dysprosium centres of compounds 2 and 3 display a hula hoop-like geometry; however, those in 1 show the monocapped square antiprismatic geometries. Moreover, the Dy2 cores of compounds 1 and 3 were linked by μ2–η1:η1 and μ2–η1:η2 bridging modes, thus generating shorter intramolecular Dy⋯Dy distances as compared to those in compound 2. Consequently, these three compounds demonstrate distinct magnetic properties. Compounds 1 and 2 behave as single-molecule magnets (SMMs) under an appropriate static dc field; in addition, 2 displays field-induced multiple relaxation processes under a 1000 Oe dc field. Compound 3 shows a high relaxation energy barrier of 102 K in the zero dc field. These three interesting compounds with Dy2 cores shed light on the coordination geometry and magnetic interactions for the modulation of the properties of SMMs.