Search

A new hydrazone Schiff base bridging ligand (H2LSchiff (E)-N′-((1-hydroxynaphthalen-2-yl)methylene)pyrazine-2-carbohydrazide) and L/D-proline were used to construct a pair of homochiral Dy6 cluster complexes, [Dy6(CO3)(L-Pro)6(LSchiff)4(HLSchiff)2]·5DMA·2H2O (L-1, L-HPro = L-proline; DMA = N,N-dimethylacetamide) and [Dy6(CO3)(D-Pro)6(LSchiff)4(HLSchiff)2]·5DMA·2H2O (D-1, D-HPro = D-proline), which show a novel triangular Dy6 topology. Notably, the fixation of CO2 in the air formed a carbonato central bridge, playing a key role in assembling L-1/D-1. Magnetic measurements revealed that L-1/D-1 displays intramolecular ferromagnetic coupling and magnetic relaxation behaviours. Furthermore, L-1/D-1 shows a distinct magneto-optical Faraday effect and has a second harmonic generation (SHG) response (1.0 × KDP) at room temperature. The results show that the immobilization of CO2 provides a novel pathway for homochiral multifunctional 4f cluster complexes. [ABSTRACT FROM AUTHOR]

A new hydrazone Schiff base ligand was condensed from 2-hydroxy-3-methoxybenzaldehyde and pyrimidine-4-carbohydrazide {H2L = (E)-N′-(2-hydroxy-3-methoxybenzylidene)pyrimidine-4-carbohydrazide}, which was used to assemble two new Dy2 complexes Dy2L2(DMF)2(NO3)2 (1) and Dy2L2(DMF)2(AcO)2 (2). Notably, the coordinated anions have a subtle effect on the coordination configurations of the Dy3+ ions and the magnetic properties of the two Dy2 complexes. The Dy3+ ions in 1 and 2 have the same N2O5 coordination environment but show the triangular dodecahedron and the biaugmented trigonal prism coordination configurations, respectively. Magnetic measurements revealed that both 1 and 2 have intramolecular ferromagnetic interactions between the Dy3+ ions and show single-molecule magnet behaviors at 0 Oe, with Ueff/k values of 58.2 K for 1 and 59.9 K for 2. These magnetic properties may be explained by theoretical calculations. [ABSTRACT FROM AUTHOR]

Heptanuclear {GdIII7} (complex 1) and tetradecanuclear {GdIII14} (complex 2) were synthesized using the rhodamine 6G ligand HL (rhodamine 6G salicylaldehyde hydrazone) and characterized. Complex 1 has a rare disc-shaped structure, where the central Gd ion is connected to the six peripheral GdIII ions via CH3O−/μ3-OH− bridges. Complex 2 has an unexpected three-layer double sandwich structure with a rare μ6-O2− ion in the center of the cluster. Magnetic studies revealed that complex 1 exhibits a magnetic entropy change of 17.4 J kg−1 K−1 at 3 K and 5 T. On the other hand, complex 2 shows a higher magnetic entropy change of 22.3 J kg−1 K−1 at 2 K and 5 T. [ABSTRACT FROM AUTHOR]

A new Schiff base ligand, which is formed by the condensation reaction of 5-fluorosalicylaldehyde and pyrimidine-4-carbonyl hydrazide {H2LSchiff = (E)-N′-(5-fluoro-2-hydroxybenzylidene)pyrimidine-4-carbohydrazide}, was made to react with different dysprosium(III) salts in an alkaline solution to assemble Dy4 and Dy6 cluster complexes, [Dy4(OH)2(LSchiff)4(H2O)2(NO3)2]·4MeCN·MeOH (1) and [Dy6(CO3)2(LSchiff)6(H2O)3(MeOH)Cl2]·5MeOH (2), depending on whether the anion used is nitrate or chloride. Complex 1 corresponding to the nitrate anion is a butterfly-like Dy4 cluster complex with four different Dy(III) coordination configurations of [O6N2], [O8N], [O7N2] and [O6N3]; when the anion is replaced by the chloride anion, carbon dioxide can be automatically captured from the air and converted into a carbonate bridging ligand, and the final product obtained is complex 2, which is a triangular prism-type Dy6 cluster complex with double μ3-carbonate bridging ligands. Both 1 and 2 show good zero-field SMM properties, with Ueff/k values of 116.5 K for 1 and 150.9 K for 2. [ABSTRACT FROM AUTHOR]

At different reaction temperatures, using Cu(NO3)2·3H2O to react with enantiomerically pure N-donor ligands (LS/LR), respectively, two pairs of chiral one-dimensional (1D) CuII chain enantiomers formulated as [Cu(μ2-NO3)(NO3)(LS)]n/[Cu(μ2-NO3)(NO3)(LR)]n (S-1-Cu / R-1-Cu , formed at 40 °C with an NO3− group as a sole bridging ligand) and [Cu(μ2-LS)(NO3)2]n/[Cu(μ2-LR)(NO3)2]n (S-2-Cu / R-2-Cu , formed at 25 °C with LS or LR as a bridging ligand) were prepared, where LS/LR = (+)/(−)-4,5-pinenepyridyl-2-pyrazine. Interestingly, such a disparity in bridging ligands leads not only to their distinct structural features but also to their completely different magnetic couplings together with a large difference in their nonlinear optical responses. S-1-Cu with a 1D helical structure shows weak ferromagnetic coupling between CuII ions, while S-2-Cu with a 1D stairway-like structure presents weak antiferromagnetic coupling. In particular, they simultaneously possess both second- and third-harmonic generation (SHG and THG) responses in one molecule with large strength differences. More remarkably, S-1-Cu exhibits a very large THG response (162 × α-SiO2), which is 22.5 times that of S-2-Cu , and the SHG strength of S-1-Cu is more than 3 times that of S-2-Cu. This work demonstrates that reaction temperature has a great impact on the self-assembled structures of coordination polymers and subsequently results in their large performance differences. [ABSTRACT FROM AUTHOR]