Electrostatic Potential Determined Magnetic Dynamics Observed in Two Mononuclear ß-Diketone Dysprosium(III) Single-Molecule Magnets.

Two ß-diketone mononuclear Dy(III) compounds, formulated as Dy(BTFA)3(H2O)2 (1) and Dy(BTFA)3(bpy) (2) (BTFA = 3-benzoyl-1,1,1-trifluoroacetone, bpy = 2,2'-bipyridine), were prepared. Compound 1 can be identified to transform to 2 in the attendance of bpy coligand, when the local geometry symmetry of eight-coordinated Dy(III) ion changes from a dodecahedron (D2d) in 1 to a square antiprism (D4d) in 2. Fine-tuning structure aroused by auxiliary ligand has dramatical impact on magnetic properties of compounds 1 and 2. Magnetic investigations demonstrate that both 1 and 2 display dynamic magnetic relaxation of single-molecule magnets (SMMs) behavior with different effective barriers (ΔE/kB) of 93.09 K for 1 under zero direct-current (DC) field as well as 296.50 K for 1 and 151.01 K for 2 under 1200 Oe DC field, respectively. As noticed, compound 1 possesses higher effective barrier than 2, despite 1 exhibiting a lower geometrical symmetry of the Dy(III) ion. Ab initio studies reveal that the Kramers doublet ground state is predominantly axial with the gz tensors of two compounds matching the Ising-limit factor of 20 anticipated for the pure MJ = ±15/2 state. Electrostatic analysis confirms the uniaxial anisotropy directions, highlighting that the proper electrostatic distribution of the coordination sphere around Ln(III) center is the critical factor to improve the magnetic anisotropy and determine the dynamic behaviors of SMMs.

Eu-MOFs with 2-(4-carboxyphenyl)imidazo[4,5-f]-1,10-phenanthroline and ditopic carboxylates as coligands: synthesis, structure, high thermostability, and luminescence properties.

Hydrothermal reactions of europium(III) salt with 2-(4-carboxyphenyl)imidazo[4,5-f]-1,10-phenanthroline and dicarboxylic acid as coligands-benzene-1,4-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 2,5-dibromoterephthalic acid, and naphthalene-1,4-dicarboxylic acid-lead to four europium fluorescent materials (1-4). Structural analyses reveal that 1-4 have binuclear 3D metal-organic frameworks with different channels, void volumes, and conjugated structures tuned by ditopic carboxylates. There are no latticed and coordinated water molecules occurring in 1-3, while the free water molecules fill in 1D channels of 4. 4' was readily obtained via water removal of 4. Thermal analyses of all compounds show the high thermal stability of the main framework up to 450 °C. Optical studies indicate that 1-4 and 4' show the characteristic red luminescence emission of the Eu(III) ion in the visible regions at room temperature. On the basis of emission spectra, their luminescence lifetimes were determined. In particular, compound 4' shows a longer lifetime (τ = 0.942 ms) and significantly enhanced quantum yield (39%) compared with those of 1 (11%, 0.770 ms), 2 (4%, 0.414 ms), 3 (18%, 0.807 ms), and 4 (26%, 0.858 ms).

Bis[(1-methyl-1H-tetra-zol-5-yl)sulfan-yl]methane.

The mol-ecule of the title compound, C(5)H(8)N(8)S(2), lies on a twofold rotation axis that relates on 1-methyl-tetra-zolyl group to the other; the five-membered rings are twisted by 53.1 (1)°.

Poly[[diaquadi-µ(2)-cyanido-bis-(µ(2)-pyrazine-2-carboxyl-ato)dicopper(I)copper(II)] dihydrate].

In the title compound, {[Cu(II)Cu(I) (2)(C(5)H(3)N(2)O(2))(2)(CN)(2)(H(2)O)(2)]·2H(2)O}(n), the Cu(II) atom lies on an inversion centre and is octa-hedrally coordinated by two N atoms and two O atoms from opposing pyrazine-2-carboxyl-ate (2-pac) ligands and two water O atoms. The Cu(I) atom has a triangular geometry, coordinated by one N atom and one C atom from two bridging cyanide ligands, and another N atom from the 2-pac ligand. The three-dimensional structure features a succession of two-dimensional sheets containing [Cu(CN)](n) chains linked by Cu(2-pac)(2)(H(2)O)(2) groups. The coordinated and free water mol-ecules are involved in an extended three-dimensional hydrogen-bond network with the 2-pac ligands.

catena-Poly[[[tetra-aqua-iron(II)]-µ-5,5'-diazenediylditetra-zolido] dihydrate].

In the title compound, {[Fe(C(2)N(10))(H(2)O)(4)]·2H(2)O}(n), the coordin-ation geometry around the Fe(II) atom, which lies on a center of inversion, is distorted octa-hedral, with bonds to four O atoms and two N atoms. The azotetra-zolate ligand displays a bridging coordination mode, forming an infinite zigzag chain. Inter-molecular O-H⋯O and O-H⋯N hydrogen bonding and offset face-to-face π-π stacking inter-actions [centroid-centroid distance = 3.4738 (13) Å] lead to a three-dimensional network.

A new high-nitrogen compound [Mn(ATZ)(H2O)4] x 2H2O: synthesis and characterization.

A new high-nitrogen compound [Mn(ATZ)(H(2)O)(4)] x 2H(2)O (ATZ=5,5-azotetrazolate) was synthesized. Crystal structure and elemental, IR and thermal analyses were investigated in the present work. It crystallized in triclinic space group P-1 with lattice parameters a=6.304(2)A, b=7.004(2)A, c=7.921(3)A, alpha=76.114(5) degrees , beta=74.023(5) degrees , gamma=69.254(4) degrees . TG-DTG and DSC measurements are employed to postulate the thermal decomposition mechanism. The thermal decomposition kinetics of the main exothermic reaction was investigated by non-isothermal method and obtained its enthalpy of decomposition and the probable kinetic mechanism. An attempt was made to incorporate the relation between thermal stability and the structure.

Tuning of Exchange Coupling and Switchable Magnetization Dynamics by Displacing the Bridging Ligands Observed in Two Dimeric Manganese(III) Compounds.

Two Mn(III)-based dimers, [Mn2(bpad)2(CH3O)4]n (1) and [Mn2(bpad)2(pa)2]n·2H2O (2) (Hbpad = N3-benzoylpyridine-2-carboxamidrazone, H2pa = phthalic acid), have been assembled from a tridentate Schiff-base chelator and various anionic coligands. Noteworthily, compound 1 could be identified as a reaction precursor to transform to 2 in the presence of phthalic acid, resulting in a rarely structural conversion process in which the bridges between intradimer Mn(III) ions alter from methanol oxygen atom with µ2-O mode in 1 (Mn Mn distance of 3.046 Å) to syn-anti carboxylate in 2 (Mn Mn distance of 4.043 Å), while the Mn(III) centers retain hexa-coordinated geometries with independently distorted octahedrons in two compounds. The dc magnetic determinations reveal that ferromagnetic coupling between two metal centers with J = 1.31 cm-1 exists in 1, whereas 2 displays weak antiferromagnetic interactions with the coupling constant J of -0.56 cm-1. Frequency-dependent ac susceptibilities in the absence of dc field for 1 suggest slow relaxation of the magnetization with an energy barrier of 13.9 K, signifying that 1 features single-molecule magnet (SMM) behavior. This work presents a rational strategy to fine-tune the magnetic interactions and further magnetization dynamics of the Mn(III)-containing dinuclear units through small structural variations driven by the ingenious chemistry.

An Ag(I) energetic metal-organic framework assembled with the energetic combination of furazan and tetrazole: synthesis, structure and energetic performance.

A novel Ag(I) energetic MOF [Ag16(BTFOF)9]n·[2(NH4)]n () assembled with Ag(iI ions and a furazan derivative, 4,4'-oxybis[3,3'-(1H-5-tetrazol)]furazan (H2BTFOF) was successfully synthesized and structurally characterized, featuring a three-dimensional porous structure incorporating ammonium cations. The thermal stability and energetic properties were determined, revealing that the 3D energetic MOF had an outstanding insensitivity (IS > 40 J), an ultrahigh detonation pressure (P) of 65.29 GPa and a detonation velocity (D) of 11.81 km cm(-3). In addition, the self-accelerating decomposition temperature (TSADT) and the critical temperature of thermal explosion (Tb) are also discussed in detail. The finding exemplifies that the assembly strategy plays a decisive role in the density and energetic properties of MOF-based energetic materials.

[Spectra of rare earth complexes RE(Et2 dtc),3 (phen)].

The ternary solid complexes RE(Et2dtc)3 (phen) (RE=La, Pr, Nd, Sm-Er) were synthesized with sodium diethyldithiocarbamate (NaEt2 dtc x 3H2O), 1,10-phenanthroline (o-phen x H2O) and hydrated lanthanide chlorides in absolute ethanol by improved reported method. IR results revealed that RE3+ coordinated with sulfur atoms of NaEt2 dtc and nitrogen atoms of o-phen. As for UV spectrum of the complexes, energy transfer between o-phen and RE3+ was the primary process, and the main absorption peaks showed a slight red shift compared to that of o-phen; FS spectrum, as a comparison, showed that the complexes Sm (Et2 dtc)3 (phen) and Eu(Et2dtc)3 (phen) have a higher efficiency of intermolecular energy transfer and a stronger fluorescence character.

[FTIR studies of L-threonic acid and its metal compounds].

Highly pure solid compounds, such as L-threonic acid, calcium L-threonate, magnesium L-threonate, manganese L-threonate, cobalt L-threonate, nickel L-theronate, and zinc L-threonate, were prepared, wherein, L-threonic acid was obtained from calcium L-threonate by strong acid type ion exchange process, calcium L-threonate or zinc L-threonate was prepared by alcohol extracting the concentrated filter liquor of the reaction of Vc, H2O2 and CaCO3 or ZnCO3, the reminder of the compounds were synthesized using alcohol extracting the concentrated solution derived from the reaction of L-threonic acid solution, prepared by double decomposition reaction of calcium L-threonate with oxalic acid, and superfluous MgO, MnCO3, Co2(OH)2CO3 and Ni2(OH)2CO3. The compositions of the compounds were determined by chemical and elemental analysis, and these compounds have the formula M(C4H7O5)2.nH2O (M = Ca, Zn, n = 0; M = Mg, Mn, Co, n = 1; M = Ni, n = 2). The purity of the compounds was 99.60% by HPLC. The IR spectra of the complexes were similar with each other but different from that of L-threonic acid. The characteristic absorption peaks of water were not observed in those of calcium L-threonate or zinc L-threonate, which showed that the molecule of water was not involved in the complexes. Further analyses indicate that M2+ in the compounds coordinated to oxygen atom of the carboxy group, while the proton of the carboxyl group was dissociated and the proton belonging to hydroxyl was not M2+ coordinated to L-threonic acid through the sp3 hybrizated fashion. It was assumed that the coordination number of M2+ was 4.

Nanoporous lanthanide-carboxylate frameworks based on 5-nitroisophthalic acid.

The reactions of lanthanide nitrates with 5-nitroisophthalic acid (ab. 5-H(2)nip) in DMF and ethanol (1 : 1) mixed solution gave rise to three nanoporous lanthanide polymers, {[Ln(2)(5-nip)(3)(DMF)(4)](DMF)(2)}(n) (Ln = Nd (), Dy (), Ho (), 5-nip = 5-nitroisophthalate). Single-crystal X-ray diffraction analyses reveal that they are isomorphous and feature three-dimensional metal-organic frameworks with two-dimensional intersecting channels occupied by guest DMF molecules constructed from the linkage of dimer Ln(2)C(6)O(12) SBUs and 5-nip ligands. The guest DMF molecules can be reversibly removed from as identified using TGA-DSC and PXRD. The heat of adsorption of the guest-free sample of with DMF was measured with a value of 10.3 kJ mol(-1) by an RD496-III type microcalorimeter. In addition, the photoluminescent property of was investigated.