1,721,325 research outputs found
Air-stable Four-Coordinate Cobalt(II) Single-Ion Magnets
No full textFor single ion magnets (SIMs), understanding the effects of the local coordination environment and ligand field on magnetic anisotropy is key to controlling their magnetic properties. Here we present a series of tetracoordinate cobalt(II) complexes of the general formula [FL2Co]X2 (where FL is a bidentate diamido ligand) whose electron-withdrawing -C6F5 substituents confer stability under ambient conditions. Depending on the cations X, these complexes adopt structures with greatly varying dihedral twist angle between the N-Co-N' chelate planes in the solid state (48.0 to 89.2°). AC and DC field magnetic susceptibility measurements show this to translate into very different magnetic properties, the axial zero-field splitting (ZFS) parameter D ranging from -69 cm-1 to -143 cm-1 with substantial or negligible rhombic component E, respectively. A close to the orthogonal arrangement of the two {N,N'}-chelating - and -donor ligands at the Co(II) ion is found to raise the energy barrier for magnetic relaxation to above 400 K. Multireference ab-initio methods were employed to describe the complexes’ electronic structures, and the results were analyzed within the framework of ab-initio ligand field theory to probe the nature of the metal-ligand bonding and spin-orbit coupling. A relationship between the energy gaps of the first few electronic transitions and the ZFS was established, and the ZFS was correlated with the dihedral angle as well as with the metal-ligand bonding variations, viz. the two angular overlap parameters and . These findings not only give rise to a Co(II) SIM showing open hysteresis up to 3.5 K at a sweep rate of 30 Oe/s, but they also provide design guidelines for Co(II) complexes with favorable SIM signatures or even switchable magnetic relaxation properties
Systematic status of the rare Himalayan wolf snake Lycodon mackinnoni Wall 1906 (Serpentes: Colubridae)
No full textNawani, Swati, Deepak, V., Gautam, Kumudani Bala, Gupta, Sandeep Kumar, Boruah, Bitupan, Das, Abhijit (2021): Systematic status of the rare Himalayan wolf snake Lycodon mackinnoni Wall 1906 (Serpentes: Colubridae). Zootaxa 4966 (3): 305-320, DOI: https://doi.org/10.11646/zootaxa.4966.3.
FIGURE 1 in Systematic status of the rare Himalayan wolf snake Lycodon mackinnoni Wall 1906 (Serpentes: Colubridae)
No full textFIGURE 1. Distributional map of Lycodon mackinnoni based on published records and the present study. (See Appendix 1 for locality records).Published as part of Nawani, Swati, Deepak, V., Gautam, Kumudani Bala, Gupta, Sandeep Kumar, Boruah, Bitupan & Das, Abhijit, 2021, Systematic status of the rare Himalayan wolf snake Lycodon mackinnoni Wall 1906 (Serpentes: Colubridae), pp. 305-320 in Zootaxa 4966 (3) on page 307, DOI: 10.11646/zootaxa.4966.3.3, http://zenodo.org/record/473666
FIGURE 8B in Identification of anuran species diversity of the Panna Tiger Reserve, Central India, using an integrated approach
No full textFIGURE 8B. Maximum Likelihood tree based on the 16S mitochondrial DNA dataset (nodes having>50% bootstrap values are shown) of genera B. Sphaerotheca (Red colour indicates sequences generated in this study).Published as part of Prasad, Vishal Kumar, Gautam, Kumudani Bala, Gupta, Sandeep Kumar, Murthy, R. Sreenivasa, Ramesh, K., Shinde, Ajinkya Duttatray & Das, Abhijit, 2020, Identification of anuran species diversity of the Panna Tiger Reserve, Central India, using an integrated approach, pp. 450-476 in Zootaxa 4851 (3) on page 466, DOI: 10.11646/zootaxa.4851.3.2, http://zenodo.org/record/448723
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Hourglass-Shaped Homo- and Heteronuclear Nonanuclear Lanthanide Clusters: Structures, Magnetism, Photoluminescence, and Theoretical Analysis
No full textSingle-molecule magnets within polyoxometalate-based frameworks
No full textTwo polyoxometalate-based frameworks containing holmium and terbium are synthesized. Their single-molecule magnet (SMM) properties are investigated, where weak field-induced SMM behaviour is observed at low temperatures in dynamic magnetic studies.As an extension of our interest in polyoxometalates (POMs) and lanthanoids, we report the design and synthesis of two polyoxometalate-based frameworks under hydrothermal conditions; [Ho 4 (PDA) 4 (H 2 O) 11 ][(SiO 4 )@W 12 O 36 ]·8H 2 O (1) and [Tb 4 (PDA) 4 (H 2 O) 12 ][(SiO 4 )@W 12 O 36 ]·4H 2 O (2) (H 2 PDA = 1,10-phenanthroline-2,9-dicarboxylic acid). Both hybrids have been characterized by elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and powder/single-crystal X-ray diffraction. According to the structural analysis, 1 and 2 consist of 2D-cationic coordination polymers based on the respective lanthanoids and PDA 2− as well as Keggin anions that reside in the interspaces between two adjacent layers as discrete counterions connected by extensive hydrogen bonding. Although the overall structures of 1 and 2 are composed of cationic and anionic layers, there are many differences in the cationic layers such as various coordination modes of PDA 2− , different void shapes, and the existence of dinuclear Tb( iii ) units only in 2. Frameworks 1 and 2 were further characterized by dc and ac magnetic measurements and both exhibit slow relaxation of magnetization at low temperatures under an applied dc field. Their single-molecule magnet (SMM) properties are investigated, where weak field-induced SMM behaviour is observed at low temperatures in dynamic magnetic studies.Two polyoxometalate-based frameworks containing holmium and terbium are synthesized. Their single-molecule magnet (SMM) properties are investigated, where weak field-induced SMM behaviour is observed at low temperatures in dynamic magnetic studies.As an extension of our interest in polyoxometalates (POMs) and lanthanoids, we report the design and synthesis of two polyoxometalate-based frameworks under hydrothermal conditions; [Ho 4 (PDA) 4 (H 2 O) 11 ][(SiO 4 )@W 12 O 36 ]·8H 2 O (1) and [Tb 4 (PDA) 4 (H 2 O) 12 ][(SiO 4 )@W 12 O 36 ]·4H 2 O (2) (H 2 PDA = 1,10-phenanthroline-2,9-dicarboxylic acid). Both hybrids have been characterized by elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and powder/single-crystal X-ray diffraction. According to the structural analysis, 1 and 2 consist of 2D-cationic coordination polymers based on the respective lanthanoids and PDA 2− as well as Keggin anions that reside in the interspaces between two adjacent layers as discrete counterions connected by extensive hydrogen bonding. Although the overall structures of 1 and 2 are composed of cationic and anionic layers, there are many differences in the cationic layers such as various coordination modes of PDA 2− , different void shapes, and the existence of dinuclear Tb( iii ) units only in 2. Frameworks 1 and 2 were further characterized by dc and ac magnetic measurements and both exhibit slow relaxation of magnetization at low temperatures under an applied dc field. Their single-molecule magnet (SMM) properties are investigated, where weak field-induced SMM behaviour is observed at low temperatures in dynamic magnetic studies
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