Single-molecule magnet behaviour in a centrosymmetric dinuclear dysprosium(III) complex: sequential differentiation of triple relaxation pathways.

A dinuclear complex with the formula Dy2L2(H2L)Cl2(EtOH)2 (Dy2) has been synthesized by reacting DyCl3·H2O with a ligand H2L (H2L = N,N'-ethylenebis(salicylideneimine)) using ethanol as the solvent. Its crystal structure can be viewed as a dimer of two Dy(III) fragments, where each Dy(III) site shows a N2O6Cl coordination sphere with a pentagonal bipyramid geometry (D5h). Magnetic measurements reveal that Dy2 behaves as a single-ion magnet (SIM) under a zero field. When the field is applied, the ac magnetic susceptibilities show double and triple peaks under high (≥600 Oe) and low (<600 Oe) dc fields, respectively. In contrast to the common double relaxation pathways in SIMs, such multiple and intricate relaxation pathways have not been reported yet in the previous literature. In this work, by experimental analysis of the ac signals, we attribute the three slow relaxation pathways to quantum tunnelling of magnetization (QTM), intermolecular dipole-dipole interaction and spin reversal, respectively. In addition, ab initio calculations are used to elucidate the magnetic behaviours of Dy2. Overall, our work indicates that the interpretation of the relaxation process using double relaxation pathways is incomplete and difficult in previously reported literature.

Complete mitogenome of Treron sphenurus (Aves, Columbiformes): the first representative from the genus Treron, genomic comparisons and phylogenetic analysis of Columbidae.

The wedge-tailed green pigeon (Treron sphenurus) has a protective value in the evolution of the family Columbidae. In this study, the complete mitogenome of T. sphenurus from Baise City, China, which represents the first sequenced species of the genus Treron in Tribe Treronini, is reported. This was accomplished using PCR-based methods and a primer-walking sequencing strategy with genus-specific primers. The mitogenome was found to be 18,919 bp in length comprising 37 genes, including 13 protein-coding genes, two rRNA genes, 22 tRNA genes, and one control region. In terms of structure and composition, many similarities were found between the T. sphenurus and Hemiphaga novaeseelandiae (New Zealand pigeon) mitogenomes. This was further supported by phylogenetic analysis showing that T. sphenurus has a close evolutionary relationship with H. novaeseelandiae. The complete mitogenome of T. sphenurus reported here is expected to provide valuable molecular information for further studies on the phylogeny of the genus Treron and for analyses of the taxonomic status of the family Columbidae.

Reversible Switching of Single-Molecule Magnetic Behaviour by Desorption/Adsorption of Solvent Ligand in a New Dy(III)-Based Metal Organic Framework.

Two metal-organic frameworks (MOFs), [Dy(BDC)(NO3)(DMF)2] n (1, H2BDC = terephthalic acid) and [Dy(BDC)(NO3)] n (1a), were synthesized. The structures of MOFs 1 and 1a are easy to be reversibly transformed into each other by the desorption or adsorption of coordination solvent molecules. Accordingly, their magnetic properties can also be changed reversibly, which realizes our goals of manipulating on/off single-molecule magnet behaviour. MOF 1 behaves as a single-molecule magnet either with or without DC field. Contrarily, no slow magnetic relaxation was observed in 1a both under zero field and applied field.

Study on the Magneto-Structural Correlation of a New Dinuclear Cobalt(II) Complex with Double µ-Phenoxo Bridges.

A new µ-phenoxo-bridged dinuclear cobalt(II) complex, [Co2(L)2(acac)2(H2O)] (1), has been synthesized by employing a new ligand, (4-methyl-2-formyl-6-(((2-trifluoromethyl)phenyl)methyliminomethyl) phenol) (HL). Structural analysis of complex 1 reveals that the geometry around cobalt centers is best described as a distorted octahedron and the distance of cobalt neighbors is 3.128(0) Å. The magnetic property studies indicate that complex 1 exhibits strong spin-orbit coupling effects and weak ferromagnetic coupling between two high-spin Co(II) centers linked by double µ-Ophenoxo bridges, with J = 1.87(2) cm-1. The studies show that not only the Co-O-Co angle affects the alignment of the cobalt spins but also the dihedral angle between the CoOCo plane and the phenyl plane plays an important role in the magnetic coupling in this [Co2O2] system. Thus, the small bridging angles (96.96(11) and 96.91(11)°) and the large dihedral angles between the CoOCo plane and the phenyl plane (63.0(1) and 30.6(1)°) induce intramolecular ferromagnetic exchange interaction in complex 1.