- Tetranuclear lanthanide (III) complexes containing dimeric subunits: Single-molecule magnet behavior for the Dy4 analogue
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The reaction of the lanthanide(III) salts [Dy(III), Tb(III), and Gd (III)] with a hetero donor chelating ligand N′-(2-hydroxy-3-methoxybenzylidene)- 6-(hydroxymethyl) picolinohydrazide (LH3) and pivalic acid (PivH) in the presence of tetra-n-bu
- Chandrasekhar, Vadapalli,Das, Sourav,Dey, Atanu,Hossain, Sakiat,Sutter, Jean-Pascal
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- CHEF induced highly selective and sensitive turn-on fluorogenic and colorimetric sensor for Fe3+
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A new fluorescent probe was synthesized from rhodamine-6G and 6-(hydroxymethyl) picolinohydrazide for the sensing of Fe3+ in an aqueous environment. The structure of the sensor was confirmed through its single crystal X-ray study. It exhibits a high specificity and sensitivity towards Fe3+ over other interfering heavy and transition metal ions (HTM). The turn-on greenish-yellow fluorescence and a colorimetric change from colourless to pink were observed upon addition of Fe3+ which evokes almost 116- and 23-fold enhancement in absorbance and emission intensity respectively in an acetonitrile-water (1: 1, v/v, 25 °C) solution at a neutral pH (pH = 7.2). The Fe3+ promoted ring opening of the spirolactam framework to the open chain amide platform of the sensor is responsible for its visible colour change and turn-on fluorescence activity. It also exhibits an excellent performance in the dip stick method. Moreover the limit of detection of the probe is in the 10-8 M range.
- Goswami, Shyamaprosad,Das, Sangita,Aich, Krishnendu,Sarkar, Deblina,Mondal, Tapan Kumar,Quah, Ching Kheng,Fun, Hoong-Kun
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- Tetranuclear [2×2] square-grid lanthanide(III) complexes: Syntheses, structures, and magnetic properties
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The reactions of lanthanide(III) nitrate salts (DyIII, Tb III, GdIII, and ErIII) with the aroylhydrazone-based multidentate ligand 6-(hydroxymethyl)-N′-[1-(pyridin- 2-yl)ethylidene]picolinohydrazide (LH2) in the presence of Et 3N in a molar ratio of 1:1:4 afforded a series of homometallic tetranuclear lanthanide(III) complexes, [Ln4(LH)4(μ 2-OH)3(μ2-OMe)]4NO 3·xMeOH·yH2O (1, Ln = Dy, x = 2, y = 4; 2, Ln = Tb, x = 2, y = 4; 3, Ln = Gd, x = 2, y = 5; and 4, Ln = Er, x = 3, y = 3). X-ray diffraction studies revealed that all of the complexes contain a tetracationic [2×2] square-grid-like [Ln4(μ2-OH) 3(μ2-OMe)(μ2-O)4] 4+ core, which is assembled by the concerted coordination action of four monoanionic [LH]- ligands along with three μ2-OH ligands and a μ2-OMe ligand. All of the lanthanide centers are eight-coordinate and adopt distorted triangular-dodecahedral coordination geometries with two different types of coordination environments (6O,2N and 4O,4N). The magnetic susceptibility measurements of the complexes reveal both the presence of all-antiferromagnetic coupling interactions as well as both isotropic (3) and anisotropic (1, 2, 4) single-ion contributions, which do not result in slow relaxation characteristics typical of single-molecule magnets. The reactions of a multicompartmental ligand with rare-earth(III) nitrate salts afford a series of homometallic Ln4 complexes [Ln = Dy, Tb, Gd, and Er] with [2×2] square-grid topology. Magnetic studies reveal the presence of all-antiferromagnetic exchange interactions and ligand-field-induced effects for the Dy, Tb, and Er complexes, whereas an isotropic model suffices for the Gd complex.
- Biswas, Sourav,Das, Sourav,Chandrasekhar, Vadapalli,Van Leusen, Jan,Koegerler, Paul
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- Single molecule magnet behavior and magnetic refrigeration of carbonyl oxygen-bridged tetranuclear lanthanide complexes
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Three square-shape tetranuclear lanthanide complexes: {[Ln4(L)4(CH3O)4]·4CH3OH} (Ln = Gd (1), Tb(2), Dy (3); L =N′-(2-hydroxy-5-methylbenzylidene)-6-(hydroxymethyl)picolinohydrazide) were fabricated and structurally characterized. The [Ln4O8] core of complexes1-3was held together by four μ2carbonyl oxygen atoms from the L2?ligands and four μ2methanol oxygen atoms. Magnetic studies reveal that compound1exhibits cryogenic magnetic refrigeration property (?ΔSm= 30.20 J K?1kg?1), and3shows ferromagnetic interactions. Slow magnetic relaxation behaviors are observed in3. Also, compound3exhibits an energy barrier of ΔE/kB= 54.3 K and the preexponential factorτ0= 4.77 × 10?6s.
- Yang, Chen,Wei, Yu-Heng,Xu, Shuang,Zhang, Hao-Yu,Yang, Yue-Qi,Zhang, Bo,Fang, Ming
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supporting information
p. 14103 - 14110
(2021/08/16)
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- A series of [2 × 2] square grid Ln III 4 clusters: A large magnetocaloric effect and single-molecule-magnet behavior
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A series of [2 × 2] square grid LnIII4 clusters based on a multidentate chelating ligand N′-(2-hydroxybenzylidene)-6-(hydroxymethyl)picolinohydrazide (H3L), namely [Ln4(HL)4(μ2-CH3O)4]·4CH3OH (LnIII = Gd (1), Tb (2), Dy (3), and Ho (4)), were successfully synthesized and characterized by single-crystal X-ray diffraction and SQUID magnetometry. The X-ray structural analysis reveals that clusters 1-4 are mainly composed of four LnIII ions which are interconnected through four μ-O bridging picolinoyl hydrazine ligands and four μ-O bridging methoxide ions. Magnetic studies show that cluster 1 exhibits antiferromagnetic exchange interactions between nearby GdIII centers and displays a large magnetic entropy (-ΔSm = 34.46 J kg-1 K-1 for ΔH = 7.0 T at 2.0 K). Alternating current (ac) magnetic susceptibility measurements demonstrate that slow relaxation behavior occurs in 3 under a zero direct-current (dc) field, with an effective energy barrier (ΔE/kB) of 42.76 K and a pre-exponential factor of τ0 = 1.02 × 10-6 s, while in clusters 2 and 4, no out-of-phase (χ′′) signals are observed.
- Wang, Wen-Min,Li, Xian-Zhen,Zhang, Li,Chen, Jia-Li,Wang, Jun-Hua,Wu, Zhi-Lei,Cui, Jian-Zhong
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supporting information
p. 7419 - 7426
(2019/05/24)
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- Tetranuclear [2×2] square-grid lanthanide(III) complexes: Syntheses, structures, and magnetic properties
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The reactions of lanthanide(III) nitrate salts (DyIII, TbIII, GdIII, and ErIII) with the aroylhydrazone-based multidentate ligand 6-(hydroxymethyl)-N-[1-(pyridin-2-yl)ethylidene]picolinohydrazide (LH2) in the presence of Et3N in a molar ratio of 1:1:4 afforded a series of homometallic tetranuclear lanthanide(III) complexes, [Ln4(LH)4(μ2-OH)3(μ2-OMe)]4NO3·xMeOH·yH2O (1, Ln = Dy, x = 2, y = 4; 2, Ln = Tb, x = 2, y = 4; 3, Ln = Gd, x = 2, y = 5; and 4, Ln = Er, x = 3, y = 3). X-ray diffraction studies revealed that all of the complexes contain a tetracationic [2×2] square-grid-like [Ln4(μ2-OH)3(μ2-OMe)(μ2-O)4]4+ core, which is assembled by the concerted coordination action of four monoanionic [LH]- ligands along with three μ2-OH ligands and a μ2-OMe ligand. All of the lanthanide centers are eight-coordinate and adopt distorted triangular-dodecahedral coordination geometries with two different types of coordination environments (6O,2N and 4O,4N). The magnetic susceptibility measurements of the complexes reveal both the presence of all-antiferromagnetic coupling interactions as well as both isotropic (3) and anisotropic (1, 2, 4) single-ion contributions, which do not result in slow relaxation characteristics typical of single-molecule magnets.
- Biswas, Sourav,Das, Sourav,Van Leusen, Jan,K?gerler, Paul,Chandrasekhar, Vadapalli
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p. 4159 - 4167
(2015/04/27)
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- Rhombus-shaped tetranuclear [Ln4] complexes [Ln = Dy(III) and Ho(III)]: Synthesis, structure, and SMM behavior
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The reaction of a new hexadentate Schiff base hydrazide ligand (LH 3) with rare earth(III) chloride salts in the presence of triethylamine as the base afforded two planar tetranuclear neutral complexes: [{(LH)2Dy4}(μ2
- Chandrasekhar, Vadapalli,Hossain, Sakiat,Das, Sourav,Biswas, Sourav,Sutter, Jean-Pascal
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p. 6346 - 6353
(2013/07/11)
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