Search results for "antiferromagnetism"
showing 10 items of 471 documents
Discrete and 1D coordination polymeric chloro-bridged copper(II) dimers exhibiting ferro- and antiferromagnetic exchange coupling: Magneto-structural…
2009
The synthesis and characterization of two 1D coordination polymers [Cu 2 (MHL)Cl 2 ][ClO 4 ] 2 · CH 3 CN · THF ( 2 · CH 3 CN · THF) and [Cu 2 (MPyPz)Cl 2 ][ClO 4 ] 2 · CH 3 CN ( 3 · CH 3 CN), having repetitive { Cu 2 II ( μ -Cl ) 2 } units, of m -xylyl-based ligands with terminal tridentate (2-pyridyl)alkylamine (MHL = α,α′-bis[ N -(2-pyridylethyl)- N -(2-pyridylmethyl)amino]- m -xylene) and (2-pyridyl)alkylamine/pyrazole (MPyPz = α,α′-bis[ N -(2-pyridylethyl)- N -(pyrazol-1-ylmethyl)amino]- m -xylene) coordination have been accomplished. X-ray crystallographic studies reveal that the copper(II) centers in the recently reported dichloro-bridged discrete { Cu 2 II ( μ -Cl ) 2 } complex […
Polypyridyl-based Cu(II) coordination polymers: Synthesis, structural and magnetic characterizations
2015
Abstract New Cu(II) coordination polymeric neutral chains of formula [Cu 2 (1,4-tpbd)Cl 2 L 2 ] (1,4-tpbd = N,N,N ′ N ′-tetrakis(2-pyridylmethyl)benzene-1,4-diamine, L = 1,1,3,3-tetracyano-2-ethoxypropenide (tcnoet) − ( 1) or 1,1,3,3-tetracyano-2-propoxypropenide (tcnopr) − ( 2 )) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction and magnetic measurements. The crystal structure determinations of 1 and 2 reveal in both cases a one-dimensional structure in which the 1,4-tpbd acts as a bis-chelating ligand and the two chloride anions as asymmetrical bridging ligands. The Cu⋯Cu distances through the bis-chelating 1,4-tpbd ligand (8.194(1) and 8.245(3) A for 1 …
Mono- and Di-chloro-bridged Discrete Dimers and Trimers and Mono-Chloro-Bridged 1D-Coordination Polymer of Copper(II). Magneto-structural Studies
2014
The synthesis, structural characterization, and magnetic properties of three copper(II) complexes, a mono-chloro-bridged [Cu2II(L6)2(μ-Cl)(Cl)(CuIICl4)] (1) and a dichloro-bridged [CuII2(L7)2(μ-Cl)2][ClO4]2 (3) discrete trimers and dimers, and a mono-chloro-bridged 1D-coordination polymer [CuII(L6)(μ-Cl)][ClO4]·CH3CN (2), are reported. Molecular structures were authenticated by X-ray crystallography. Temperature-dependent magnetic measurements carried out on powdered samples of 1–3 indicated a very weak antiferromagnetic exchange-coupling within the {CuII(μ-Cl)CuII(μ-Cl)CuIICl3}+ units in 1 [Curie-Weiss plot: θ = –0.19(1) K and g = 2.07(1)], a ferromagnetic behavior within {CuII(μ-Cl)2CuII}…
Assembling Magnetic Blocks: A Strategy to Control the Nuclearity and Magnetic Properties of Polynuclear Complexes
1996
Synthetic strategies dealing with the polymerization of either di-μ-hydroxocopper(II) complexes or 2,2′-bipyrimidine (bpym)-containing first row transition metal ions allow the preparation of polynuclear compounds whose structures and magnetic properties are presented here. The influence of structural and chemical parameters on the magnitude of the singlet-triplet energy gap (J) in di-μ-hydroxocopper(II) complexes [LCu(OH)2CuL]2+ with L = 2,2′-bipyridine (bpy) and bpym is analyzed and discussed. Special attention is devoted to nature of the counterion which allows the preparation of hydroxo-bridge copper(II) cubane and double cubane type complexes where all the intramolecular magnetic inter…
Experimental and Theoretical Study of Dynamic Structural Transformations between Sensing Copper(II)-Uracil Antiferromagnetic and Metamagnetic Coordin…
2020
This paper describes the synthesis and characterization of several Copper(II)-uracil-1-propionic acid (UPrOH) coordination compounds, including the theoretical and experimental study of their cryst...
From Bowls to Capsules: Assembly of Hexanuclear Ni II Rings Tailored by Alkali Cations
2020
An anionic hexanuclear NiII metallamacrocycle with endo and exo linking sites has been employed as a building block to generate a series of capsules and bowls of nanometric size. The supramolecular arrangement of the {Ni6 } rings was tailored by the size of the alkali cations, showing the transition from {Ni6 -M2 -Ni6 } capsules (M=LiI and NaI ) to {Ni6 -M} bowls (M=KI and CsI ). The alkyl co-cations are determinant to stabilize the assemblies by means of CH⋅⋅⋅π interactions on the exo side of the metallamacrocycles. The effect on the topology of the supramolecular assemblies of the cation size, cation charge, Et3 NH+ or Me4 N+ counter cations has been analyzed. Magnetic measurements reveal…
Magneto-structural versatility of copper(II)-3-phenylpropionate coordination polymers with N-donor coligands.
2015
A novel series of copper(II) coordination polymers [Cu2(O2CC8H9)4(pyz)]n (1), [Cu2(O2CC8H9)4(dps)]n (2), {[Cu(O2CC8H9)2(dps)(H2O)]·H2O}n (3), {[NaCu(O2CC8H9)2(bpm)(NO3)]·H2O}n (4), and [Cu4(O2CC8H9)6(OH)2(bpp)2]n (5) [O2CC8H9− = 3-phenylpropionate anion, pyz = pyrazine, dps = di(4-pyridyl)sulfide, bpm = 2,2′-bipyrimidine, and bpp = 1,3-bis(4-pyridyl)propane] have been synthesized and magneto-structurally investigated. Compounds 1 and 2 belong to a large group of copper(II) carboxylates where bis-monodentate pyz (1) and dps (2) ligands connect the paddle-wheel [CuII2(μ-O2CC8H9)4] units leading to alternating copper(II) chains. The structure of 3 consists of uniform chains of trans-[CuII(O2CC…
Effect of Protonated Organic Cations and Anion−π Interactions on the Magnetic Behavior of Hexabromorhenate(IV) Salts
2015
Two novel Re-IV compounds of formula (Hbpym)(2)[(ReBr6)-Br-IV]center dot 4H(2)O (1) and (H(4)biim)[(ReBr6)-Br-IV]center dot 4H(2)O (2) [Hbpym(+) = 2,2'-bipyrimidinium cation and H(4)biim(2+) = 2,2'-biimidazolium dication] have been prepared and magnetostructurally characterized. 1 and 2 exhibit distinct crystal packing, and the presence of weak intermolecular contacts, such as Re-Br...B-rRe (1 and 2), Re-Br center dot center dot center dot(H2O)center dot center dot center dot BrRe (1 and 2), and Re-Br center dot center dot center dot pi center dot center dot center dot Br-Re (2), lead to different magnetic behaviors. While 1 is antiferromagnetic, 2 is a ferromagnetic compound and indeed the…
Pentachloro(pyrazine)rhenate(iv) complex as precursor of heterobimetallic pyrazine-containing ReIV2MII (M = Ni, Cu) species: synthesis, crystal struc…
2008
Three novel Re(IV) mononuclear complexes of formulae NBu4[ReC15(pyz)] (1), NH2Me2[ReCl5(pyz)] (2) and NH4[ReCl5(pyz)].0.75H2O (3), (pyz being pyrazine; NBu4+ = tetra-n-butylammonium cation, NH2Me2+ = dimethylammonium cation and NH4+ = ammonium cation), were synthesized by ligand substitution reaction from [ReCl6]2- anion and pyrazine in N,N-dimethylformamide (DMF). In addition, two new heterobimetallic compounds, the salt namely [ReCl5(pyz)]2[Ni(cyclam)](4) (cyclam = 1,4,8,11-tetraazacyclotetradecane) and the heterotrinuclear [{ReCl5(mu-pyz)}2Cu(DMF)4] (5) complex, were prepared by using as precursor 1 and 3, respectively. Compounds 1-5 were characterized by single-crystal X-ray diffraction…
Enantioselective self-assembly of antiferromagnetic hexacopper(ii) wheels with chiral amino acid oxamates
2013
The Cu(2+)-mediated self-assembly of oxamato-based ligands derived from either the (S)- or (R)-enantiomers of the amino acid valine leads to the formation of two antiferromagnetically coupled homochiral anionic hexacopper(II) wheels in the presence of templating tetramethylammonium countercations.