Antiferromagnetism and metamagnetism in 1,4-diazine and pyridine complexes of nickel(II)

1995 ◽  
Vol 73 (2) ◽  
pp. 275-283 ◽  
Author(s):  
Tom Otieno ◽  
Robert C. Thompson
Keyword(s):  
Magnetic Properties ◽  
Electronic Spectroscopy ◽  
Antiferromagnetic Coupling ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Critical Fields ◽  
Scanning Calorimetry ◽  
Magnetic Exchange ◽  
Nickel Ions ◽  
Pyridine Complexes

Several nickel(II) complexes containing pyridine (py), pyrazine (pyz) or methylpyrazine (mepyz) have been synthesized and characterized by vibrational and electronic spectroscopy, differential scanning calorimetry, and magnetic susceptibility studies to cryogenic temperatures. A comparison of the magnetic properties of the polymeric diazine-bridged complexes, Ni(pyz)2X2 (X = Cl or NO3), Ni(pyz)(p-CH3C6H4SO3)2, Ni(mepyz)(NO3)2, and Ni(pyz)3(CH3SO3)2•CH3OH with those of the related monometallic systems, Ni(py)4X2 (X = Cl, p-CH3C6H4SO3 or CH3SO3) and Ni(mepyz)4(NO3)2•H2O provides evidence for weak antiferromagnetic coupling between metal centers mediated by bridging diazine ligands in the former group of compounds. The magnetic properties were analyzed employing a model for S = 1 which takes into account zero-field splitting and employs a molecular field term to account for weak magnetic exchange. The compounds Ni(pyz)Cl2 and Ni(py)Cl2 show metamagnetic behaviour with critical fields of 13 and 2 kOe, respectively, at 2 K. In these compounds nickel ions, linked in chains by bridging chlorides, exhibit intrachain ferromagnetic and interchain antiferromagnetic exchange. In Ni(pyz)Cl2 bridging pyrazine ligands are considered to provide the pathway for the antiferromagnetic coupling resulting in a high critical field. Keywords: nickel(II), pyrazine, pyridine, complexes, metamagnetism, antiferromagnetism.

scholarly journals Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties

2020 ◽  
Vol 6 (4) ◽  
pp. 48
Author(s):  
Lu Xi ◽  
Jing Han ◽  
Xiaohui Huang ◽  
Licun Li
Keyword(s):  
Magnetic Properties ◽  
Magnetic Relaxation ◽  
Lanthanide Complexes ◽  
Magnetic Data ◽  
Antiferromagnetic Coupling ◽  
Zero Field ◽  
Nitronyl Nitroxide ◽  
Ferromagnetic Exchange ◽  
Binuclear Structure ◽  
Slow Magnetic Relaxation

Employing a new nitronyl nitroxide biradical NITPhPzbis(NITPhPzbis = 5-(1-pyrazolyl)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene), a series of 2p-4f complexes [Ln2(hfac)6(H2O)(NITPhPzbis)] (LnIII = Gd1, Tb2, Dy3; hfac = hexafluoroacetylacetonate) were successfully synthesized. In complexes 1–3, the designed biradical NITPhPzbis coordinates with two LnIII ions in chelating and bridging modes to form a four-spin binuclear structure. Direct-current magnetic study of Gd analogue indicates that ferromagnetic exchange exists between the Gd ion and the radical while antiferromagnetic coupling dominates between two mono-radicals. Dynamic magnetic data show that the χ” signals of complex 3 exhibit frequency dependence under zero field, demonstrating slow magnetic relaxation behavior in complex 3. And the estimated values of Ueff and τ0 are about 8.4 K and 9.1 × 10−8 s, respectively.

Single-Crystal Magnetic Properties of [Co(NH3)5(OH2)] [Cr(CN)6] Between 2 and 300 K

1992 ◽  
Vol 45 (11) ◽  
pp. 1899 ◽  
Author(s):  
PA Reynolds ◽  
CD Delfs ◽  
BN Figgis ◽  
B Moubaraki ◽  
KS Murray
Keyword(s):  
Ising Model ◽  
Field Model ◽  
Mean Field ◽  
Zero Field ◽  
Spin Orbit Coupling ◽  
Zero Field Splitting ◽  
Magnetic Exchange Interaction ◽  
Mean Field Model ◽  
Magnetic Exchange ◽  
The Mean

The magnetic susceptibilities along and perpendicular to the c axis (hexagonal setting) between 2.0 and 300 K at a magnetic field of 1.00 T, and the magnetizations at field strengths up to 5.00 T, are presented for single crystals of [Co(NH3)5(OH2)] [Cr(CN)6]. The results are interpreted in terms of zero-field splitting (2D) of the ground 4A2g term by spin-orbit coupling and of magnetic exchange interaction between the chromium atoms. The magnetic exchange is modelled as one of Ising or mean-field in type. The exchange is found to be quite small: J = -0.18(6) cm-1 if the Ising model is employed, and -0.03(1) cm-1 for the mean-field model. The model adopted for the exchange has a strong influence on the value of the parameter D obtained. When the Ising model is used D is deduced to be -0.28(9) cm-l; when the mean-field model is used D is -0.14(4) cm-l. The g-values deduced are in agreement with those from e.s.r. measurements at higher temperatures and do not depend on the exchange model. In any case, D is found to be sufficiently large that it must be considered in a polarized neutron diffraction experiment on the compound.

Synthesis, structure, and magnetic properties of diphenylphosphinates of cobalt(II) and manganese(II). The crystal and molecular structures of the γ forms of poly-bis(μ-diphenylphosphinato)cobalt(II) and manganese(II)

1991 ◽  
Vol 69 (2) ◽  
pp. 277-285 ◽  
Author(s):  
Jing-Long Du ◽  
Steven J. Rettig ◽  
Robert C. Thompson ◽  
James Trotter
Keyword(s):  
Magnetic Properties ◽  
Heavy Atom ◽  
Molecular Structures ◽  
Antiferromagnetic Coupling ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Lattice Constants ◽  
Linear Chains

The synthesis of the β and γ forms of M(Ph2PO2)2 where M = Co and Mn are described and the compounds are characterized by infrared spectroscopy, differential scanning calorimetry, X-ray powder diffraction, and low-temperature (2–80 K) magnetic susceptibility studies. Single crystal X-ray diffraction studies are reported on the γ forms. Crystals of the γ forms of poly-bis(μ-diphenylphosphinato)cobalt(II) and poly-bis(μ-diphenylphosphinato)manganese(II) are isomorphous, crystallizing with 4 formula units per unit-cell in the monoclinic space group P21/c. Lattice constants are a = 8.080(2), 8.161(1), b = 23.550(6), 23.751(1), c = 11.726(3), 11.6946(6) Ǻ, and β = 92.88(2), 93.026(8)° for the Co and Mn derivatives respectively. The structures were solved by heavy atom methods and were refined by full-matrix least-squares procedures to R = 0.039 and 0.045 for 4041 and 2878 reflections with I ≥ 3σ(I), respectively. Both crystal structures consist of double phosphinate-bridged chain polymers containing tetrahedrally coordinated metal atoms: Co—O = 1.950(2)–1.963(2) Ǻ, O—Co—O = 104.81(8)–117.77(9)°, Mn—O = 2.016(3)–2.033(3) Ǻ, O—Mn—O = 103.2(1)–114.7(1)°. All four compounds exhibit antiferromagnetic coupling and magnetic susceptibilities have been analyzed according to two Heisenberg models for linear chains of metal ions with S = 3/2 for cobalt and S = 5/2 for manganese. The Weng model (with values for the Wagner and Friedberg model in parentheses) gives –J = 0.25 (0.26) cm−1 and 0.55 (0.60) cm−1 for the β and γ forms, respectively, of Co(Ph2PO2)2, and 0.34 (0.36) cm−1 and 0.17 (0.17) cm−1 for the β and γ forms, respectively, of Mn(Ph2PO2)2. Key words: crystal structure, diphenylphosphinates of cobalt(II) and manganese(II), magnetic properties.

scholarly journals ESR, Zero-Field Splitting, and Magnetic Exchange of Exchange-Coupled Copper(II)−Copper(II) Pairs in Copper(II) TetraphenylporphyrinN-Oxide#

2007 ◽  
Vol 46 (2) ◽  
pp. 578-585 ◽  
Author(s):  
Fuh-An Yang ◽  
Chih-Wei Guo ◽  
Yao-Jung Chen ◽  
Jyh-Horung Chen ◽  
Shin-Shin Wang ◽  
...  
Keyword(s):  
Zero Field ◽  
Zero Field Splitting ◽  
Magnetic Exchange ◽  
Field Splitting

Magnetic Studies in Mixed-Metal Valency Molecule Magnets NBu4FeιιnMnιι1-n[Feιιι(OX)3](n=0.03, 0.10, 0.15, 0.97)

2012 ◽  
Vol 567 ◽  
pp. 259-262 ◽  
Author(s):  
Qing Lin ◽  
Shao Hong Chen ◽  
Yun He ◽  
Xiao Gang Li ◽  
Hai Fu Huang
Keyword(s):  
Antiferromagnetic Coupling ◽  
Zero Field ◽  
Magnetization Curves ◽  
Magnetic Studies ◽  
Magnetic Exchange Interaction ◽  
Magnetic Exchange ◽  
Mixed Valency ◽  
Bridging Ligand ◽  
Bifurcation Phenomenon ◽  
Oxalate Group

The mixed valency character and antiferromagnetic coupling in Molecule magnets Materials NBu4FeIInMnII1-n[FeIII(OX)3]（n=0.03、0.10、0.15、0.97） were investigated by magnetic measurements.The values of M increase and exhibit weak irreversibility in the field-cooled (FC) magnetization curves. There are a clear bifurcation phenomenon of the field-cooled (MFC) and Zero-field-cooled (MZFC) magnetization curves.In the Molecule magnets Materials NBu4FeII0.10 MnII0.90[FeIII(OX)3],the Ne´el temperature is 34 K.And the Ne´el temperature of NBu4FeII0.15MnII0.85 [FeIII(OX)3] is 28 K.In the sample NBu4FeII0.03 MnII0.97[FeIII(OX)3],,the bifurcation of the ZFC and FC plots below the Ne´el temperature of 30 K indicates irreversibility.The oxalate group has been shown to be an excellent bridging ligand in supporting the magnetic exchange interaction.

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