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The low-temperature solvo-thermal syntheses of single-phase titania from Ti[Cl.sub.4] in ketones capable of performing aldol condensation reaction are presented.

One-dimensional ZnO nanostructures with perpendicular side facets can be easily synthesized in an approach with more complex architecture over a large scale. The synthesis involves no-template or no-substrate solution method, which allows the oriented growth of ZNO nanostructures at large-scale, low-cost, and moderate temperatures.

The self-assembly of Ln(ClO4)3·6H2O and Zn(OAc)2·2H2O with pyrazine-2-carboxylic acid (HL) results in the formation of three novel nanosized {LnIII24ZnII6} triangular metallorings, [Gd24Zn6L24(OAc)22(µ3-OH)30(H2O)14](ClO4)7(OAc)·2CH3OH·26H2O (1), [Tb24Zn6L24(OAc)22(μ3-OH)30(CH3O)2(CH3OH)2(H2O)10](ClO4)5(OH)·6CH3OH·12H2O (2), and (H3O)[Dy24Zn6L24(OAc)22(μ3-OH)30(H2O)14](ClO4)7(OAc)2·4CH3OH·22H2O (3), having the largest nuclearity among any known Ln/Zn clusters. Magnetic and luminescent studies reveal the special prowess for each lanthanide complex. Magnetic studies reveal that 1 exhibits a significant cryogenic magnetocaloric effect with a maximum -ΔSm (isothermal magnetic entropy change) value of 30.0 J kg-1 K-1 at 2.5 K and 7 T and that a slow magnetization relaxation is observed for the dysprosium analogue. In addition, the solid-state photophysical properties of 2 display strong characteristic TbIII photoluminescent emission in the visible region, suggesting that TbIII-based luminescence is sensitized by the effective energy transfer from the ligand HL to the metal centers. [ABSTRACT FROM AUTHOR]

In order to evaluate the impact of bridge conformation on electronic coupling in donor-bridge-acceptor triad systems, two Mo2 dimers, [Mo2(DAniF)3]2[μ-1,4-{C(O)NH}2-Naph] (1, DAniF = N,N'-di(p-anisyl)formamidinate and Naph = naphthalenyl) and [Mo2(DAniF)3]2[μ-1,4-(CS2)2-2,5-Me2C6H2] (2), have been synthesized and structurally characterized. These two compounds feature a large dihedral angle (>60°) between the central aromatic ring and the plane defined by the Mo-Mo bond vectors, which is distinct from the previously reported phenylene bridged analogues [Mo2(DAniF)3]2[μ-1,4-{C(O)NH}2-ph] (I) and [Mo2(DAniF)3]2[μ-1,4-(CS2)2-C6H4] (II), respectively. Unusual optical behaviors are observed for the mixed-valence (MV) species (1+ and 2+), generated by single-electron oxidation. While 2+ exhibits a weak intervalence charge transfer (IVCT) absorption band in the near-IR region, the IVCT band is absent in the spectrum of 1+, which is quite different from what observed for I+ and II+. Optical analyses, based on superexchange formalism and Hush model, indicate that, in terms of Robin-Day classification, mixed-valence species 1+ belongs to the electronically uncoupled Class I and complex 2+, with Hab = 220 cm-1, is assigned to the weakly coupled Class II. Together with I+ and II+, the four MV complexes complete a transition from Class I to Class II-III borderline as a result of manipulating the geometric topology of the bridge. Given the structural and electronic features for the molecular systems, the impacts of electrostatic interaction (through-space) and electron resonance (through-bond) on electronic coupling are discussed. [ABSTRACT FROM AUTHOR]

A family of four Dy3 triangular circular helicates, namely, [Dy3(HL)3(μ3-OH)(CH3OH)2(H2O)4]Cl1.5(OH)0.5·0.5H2O (1), [Dy3(HL)3(μ3-OH)(CH3OH)3(H2O)2Cl]Cl·CH3OH (2), [Dy3(HL)3(μ3-OH)(CH3OH)3(H2O)2(NO3)](NO3) (3), and [Dy3(HL)3(μ3-OH)(CH3OH)4(ClO4)](ClO4) (4), were assembled by the reaction of a new acylhydrazone ligand H3L [(3-hydroxy)-N'-((8-hydroxyquinolin-2-yl)methylene)picolinohydrazide] with different dysprosium(III) salts. These compounds represent the first examples of μ-Oacylhydrazone-bridged triangular Dy3 SMMs reported to date. Alternating-current magnetic susceptibility measurements revealed that compounds 1 and 2 show typical SMM behavior with the occurrence of multiple relaxation processes, whereas frequency-dependent relaxation signals without χ" peaks were observed in 3 and 4 under zero dc field. Such distinct dynamic behaviors are attributed to the different sizes of the terminal coordination solvent/anions (H2O, Cl-, NO3-, and ClO4- for 1-4, respectively) at the Dy3 site. Here, similar deviations from the ideal monocapped square-antiprismatic (C4v) geometry defined by SHAPE software were observed around local Dy centers in 1 and 2, whereas the situation was completely different in 3 and 4 as a result of the presence of relatively large anions in the limited space defined by three intercrossing rigid hydrazone ligands. [ABSTRACT FROM AUTHOR]

The reactions between a salen ligand N,N′-bis(3-methoxysalicylidene)-1,2-cyclohexanediamine (H2L) and different metal salts lead to the formation of four 3d-4f [MDy] and [MDy]2 (M = Zn/Cu) compounds, where the [MDy]2 can be considered as resulting from the assembly of two [MDy] building blocks. Field-induced single molecule magnet (SMM) behavior was observed in [ZnDy] and [CuDy] compounds with the effective suppression of fast quantum tunneling under a dc field. Moreover, the [ZnDy]2 compound demonstrates typical SMM behavior, which may originate from the high axial anisotropy of Dy ions correlating to the change of coordination geometry and enhanced ferromagnetic interactions between Dy ions via the coupling of two [DyZn] units. The result suggests the positive effects of coupling blocking units to enhance their SMM behavior, presenting a promising strategy for constructing efficient heterometallic SMMs. [ABSTRACT FROM AUTHOR]

Two new dinuclear dysprosium compounds, [Dy2(HL1)2(PhCOO)2(CH3OH)2] (l) and [Dy2(L2)2(NO3)2-(CH3OH)2]-2CH3OH-4H2O(2), have been assembled through applying two ligands with different coordination pockets. The different features of ligands H3L1 and H2L2 result in the distinct coordination geometry of the metal ions in their respective structures. The Dy ions of complexes 1 and 2 were linked by the alkoxide- and hydrazone-O, and display the hula hoop-like and the broken hula hoop-like coordination geometry, respectively. Consequendy, these two compounds show distinct magnetic properties. Complex 1 behaves as a single molecule magnet (SMM) with rather slow quantum tunneling rate (... > 274 ms), while no SMM behavior was observed for complex 2. In addition, the comparison of the structural parameters among the similar Dy2 SMMs with hula hoop-like geometry reveals the significant role played by coordination geometry and magnetic interaction in modulating the relaxation dynamics of SMMs. [ABSTRACT FROM AUTHOR]