Polynuclear pyrazolate complexes of copper. Crystal and molecular structures of [Cu(tmpz)]3, [Cu(3-CO2dmpz)(tmpzH)]2Cu, and [Cu(4-Br-3-CO2mepz)(4-Br-dmpzH)2]2 (where mepz = methylpyrazolate, dmpz = dimethylpyrazolate, and tmpz = trimethylpyrazolate) and magnetic susceptibility studies on the dinuclear complex

1992 ◽  
Vol 70 (8) ◽  
pp. 2161-2173 ◽  
Author(s):  
Martin K. Ehlert ◽  
Steven J. Rettig ◽  
Alan Storr ◽  
Robert C. Thompson ◽  
James Trotter
Keyword(s):  
Magnetic Susceptibility ◽  
Exchange Coupling ◽  
Bulk Sample ◽  
Molecular Structures ◽  
Antiferromagnetic Coupling ◽  
Coupling Constant ◽  
Copper Metal ◽  
Copper Crystal ◽  
Space Group ◽  
Crystalline Forms

The reaction of molten trimethylpyrazole (tmpzH) with copper metal shot in air yields a mixture of the trinuclear copper(I) complex [Cu(tmpz)]3, 1, and the trinuclear copper(I/II) complex [Cu(3-CO2dmpz)(tmpzH)]2Cu, 2 (where dmpz is dimethylpyrazolate). Crystals of 1 are monoclinic, a = 8.403(3), b = 22.453(2), c = 11.362(2) Å, (3 = 95.83(2)°, Z = 4, space group P21/c. Crystals of 2 are triclinic, a = 10.988(3), b = 11.009(2), c = 6.457(1) Å, α = 103.13(2)°, β = 103.02(2)°, γ = 108.70(2)°, Z = 1, space group [Formula: see text]. The reaction of molten 4-bromodimethylpyrazole (4-BrdmpzH) with copper metal shot in air gave the binuclear copper(II) complex [Cu(4-Br-3-CO)2mepz)(4-BrdmpzH)2]2, 3 (where mepz is methylpyrazolate). There are two crystalline forms of 3:3a, triclinic, a = 10.152(3), b = 13.068(3), c = 10.033(3) Å, a = 112.38(2)°, (3 = 116.46(2)°, γ = 70.29(2)°, Z = 1, space group [Formula: see text]; and 3b, monoclinic, a = 13.470(1), b = 16.005(2), c = 20.174(1) Å, β = 98.142(6)°, Z = 4, space group C2/c. Magnetic susceptibility studies on a bulk sample of 3 (2.0–300 K) revealed antiferromagnetic coupling between the double pyrazolate bridged copper centres and analysis of the data according to a Heisenberg model for coupled pairs of S = 1/2 metal ions gave −75.4 cm−1 for the value of the exchange coupling constant, J. The crystal structures of 1, 2, 3a, and 3b were solved by the Patterson method and were refined by full-matrix least-squares procedures to final R values of 0.036, 0.056, 0.042, and 0.042 for 2265, 1764, 2011, and 2575 reflections with I ≥ 3σ(I), respectively.

Structure and Spin-Spin Interactions in a Linear Trinuclear Ni(II) Complex

1996 ◽  
Vol 51 (5) ◽  
pp. 665-670 ◽  
Author(s):  
Ayhan Elmali ◽  
Yalcin Elerman ◽  
Ingrid Svoboda ◽  
Hartmut Fuess ◽  
Klaus Griesar ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Magnetic Susceptibility ◽  
Octahedral Coordination ◽  
Antiferromagnetic Coupling ◽  
Nickel Ion ◽  
Triclinic Space Group ◽  
Space Group ◽  
Spin Interactions

[Ni3(C2H3O2)2(C3H8NO)2L2] [(L=N,N′-1,3-propyl-disalicylaldimine), (C2H3O2)=acetate, (C3H8NO)=hydroxymethyl-dimethylamine] has been synthesized and its crystal structure determined, [C44H54N6O10Ni3], triclinic, space group P1̄, a = 9.560(1), b = 10.681(1), c = 12.200(1) Å, α = 112.17(1), β = 101.25(1), γ = 90.32(1)°, V = 1127.3 Å, Z = 1.The molecule is linearly trinuclear with octahedral coordination of each nickel ion. The Ni-Ni distance is 3.048( 1) Å. Each nickel(II) atom is in an octahedral coordination. Magnetic susceptibility measurements in the range 4.2 < T < 280 K have revealed antiferromagnetic coupling between adjacent Ni atoms (J1 = -2.2 cm-1) and between the terminal Ni atoms (J2 = -1.7 cm-1).

Magnetic chains formed from tetra-coordinate Co(II) complexes

2013 ◽  
Vol 67 (3) ◽  
Author(s):  
Monika Idešicová ◽  
Alžbeta Krutošíková ◽  
Viera Mrázová ◽  
Roman Boča
Keyword(s):  
Magnetic Susceptibility ◽  
Low Temperature ◽  
Exchange Interaction ◽  
Exchange Coupling ◽  
Magnetic Interaction ◽  
Donor Ligands ◽  
Coupling Constant ◽  
Exchange Coupling Constant ◽  
Π Stacking ◽  
Magnetic Chain

AbstractTwo tetra-coordinate Co(II) complexes, [CoCl2(bzfupy)2] and [CoCl2(p-tol)2] with N-donor ligands, are apparently mononuclear systems. The magnetic susceptibility at low temperature attains a maximum which is a fingerprint of the exchange interaction. The exchange coupling constant fitted to a model of 1D-magnetic chain yields J/hc = −0.50 cm−1 and −0.57 cm−1, respectively. The magnetic interaction is mediated by the π-π stacking in the first complex, and the short Cl…Cl contacts in the second.

Transition metal azolates from metallocenes. Part 3: Polymeric manganese(II) and nickel(II) pyrazolates; synthesis, characterization, and magnetochemistry

1998 ◽  
Vol 76 (8) ◽  
pp. 1130-1137 ◽  
Author(s):  
Alan Storr ◽  
David A Summers ◽  
Robert C Thompson
Keyword(s):  
Metal Ions ◽  
Exchange Coupling ◽  
Variable Temperature ◽  
Indirect Evidence ◽  
Inert Atmosphere ◽  
Magnetic Data ◽  
Antiferromagnetic Coupling ◽  
Coupling Constant ◽  
Direct Reactions ◽  
Nickel Manganese

Direct reactions of nickelocene and manganocene with molten pyrazoles in an inert atmosphere or under vacuum have led to the isolation of the following metal pyrazolate compounds: [Ni(4-Xpz)2]x (where X = H, Cl and pz = pyrazolate); [M(4-Xdmpz)2]x (where X = H, CH3, Cl, Br and M = Ni, Mn anddmpz = 3,5-dimethylpyazolate); and [Mn(4-Xpz)2(4-XpzH)]x (where X = Cl, Br and pzH = pyrazole). On the basis of indirect evidence all compounds are considered to have extended chain structures with metal ions linked in chains by double bridging pyrazolates. The two [Ni(4-Xpz)2]x compounds are diamagnetic while all others are paramagnetic. Variable temperature magnetic susceptibility studies on the paramagnetic compounds reveal antiferromagnetic coupling between neighbouring metal ions. Analysis of the magnetic data (Hamiltonian of the form H = -2J sum Si·Sj) yields values of the exchange coupling constant J of -14 to -17 cm -1for the [Ni(4-Xdmpz)2]x compounds, -1.2 to -2.1 cm-1 for the [Mn(4-Xdmpz)2]x compounds, and -0.41 cm-1 for the [Mn(4-Xpz)2(4-XpzH)]x compounds.Key words: nickel, manganese, manganocene, nickelocene, pyrazolates, antiferromagnetic exchange.

scholarly journals Assessment of density functional approximations for calculation of exchange coupling constants in thiocyanato and cyanato double bridged binuclear Ni(II) complexes

2020 ◽  
pp. 71-71
Author(s):  
Matija Zlatar ◽  
Filip Vlahovic ◽  
Dragana Mitic ◽  
Mario Zlatovic ◽  
Maja Gruden
Keyword(s):  
Magnetic Properties ◽  
Exchange Coupling ◽  
Density Functional ◽  
Coupling Constants ◽  
Antiferromagnetic Coupling ◽  
Binuclear Complexes ◽  
Coupling Constant ◽  
Symmetry Approach ◽  
Experimental Values ◽  
Broken Symmetry Approach

In the present work, we examine the magnetic properties of 8 "endto-end" thiocyanato, and 3 "end-to-end" cyanato double bridged Ni(II) binuclear complexes. Thiocyanato complexes are weakly ferromagnetic. Cyanato bridged complexes exhibit weak antiferromagnetic coupling. Therefore, it is a challenge for computational chemistry to calculate the exchange coupling constant in these systems accurately. 17 different Density Functional Approximations with different flavors are used to find the method of choice to study magnetic properties in binuclear Ni(II) complexes within the Broken-Symmetry approach. It is found that M06-2X and PWPB95 performed the best compared to experimental values for the entire set of examined complexes. Furthermore, the magneto-structural correlation rationalizes the results.

Synthesis and characterization of the mixed valence Cu(l)/Cu(ll) 3,5-bis(trifluoromethyl)-pyrazolate complex, [Cu(ll)2Cu(l)(F6dmpz)5]

1997 ◽  
Vol 75 (5) ◽  
pp. 491-498 ◽  
Author(s):  
Martin K. Ehlert ◽  
Alan Storr ◽  
David A. Summers ◽  
Robert C. Thompson
Keyword(s):  
Exchange Coupling ◽  
Mixed Valence ◽  
Direct Methods ◽  
Magnetic Data ◽  
Antiferromagnetic Exchange ◽  
Coupling Constant ◽  
Copper Metal ◽  
X Ray ◽  
R Value

The reaction of molten 3,5-bis(trifluoromethyl)pyrazole (F6dmpzH) with copper metal shot under an atmosphere of dioxygen yields the green trimetallic mixed valence [Cu(II)2Cu(1)(F6dmpz)5]. Crystals of [Cu(II)2Cu(I)(F6dmpz)5] are triclinic, a = 9.0557(2), b = 9.6164(2), c = 11.8874(3) Å, α= 105.406(1)°, β = 112.317(1)°, γ = 90.662(1)°, Z= 1, space group P͞1. The crystal structure was solved by direct methods and was refined by full-matrix least-squares procedures to a final R value of 0.0538 for 2591 reflections with I≥2σ(I). Magnetic susceptibility studies over the range 2–300 K reveal strong antiferromagnetic exchange coupling between the two copper(II) centers. Fits of the magnetic data to the Bleaney-Bowers equation for two interacting S= ½ centers gives the exchange coupling constant J = –235 cm–1. Key words: trimetallic, copper, 3,5-bis(trifluoromethyl)pyrazolates, X-ray structure, antiferromagnetism.

Metal pyrazolate polymers. Part 3. Synthesis and study of Cu(I) and Cu(II) complexes of 4-Xdmpz (where X = H, Cl, Br, I, and CH3 for Cu(I) and X = H, Cl, Br, and CH3 for Cu(II); dmpz = 3,5-dimethylpyrazolate)

1992 ◽  
Vol 70 (4) ◽  
pp. 1121-1128 ◽  
Author(s):  
Martin K. Ehlert ◽  
Alan Storr ◽  
Robert C. Thompson
Keyword(s):  
Magnetic Susceptibility ◽  
Spectroscopic Studies ◽  
Magnetic Data ◽  
Antiferromagnetic Coupling ◽  
Polymeric Chain ◽  
Differential Scanning Calorimetric ◽  
Scanning Electron Micrographs ◽  
Coupling Constant ◽  
Abrupt Decrease ◽  
Calorimetric Studies

The copper(I) complexes [Cu(4-Xdmpz)]3 (where X = H, Cl, Br, I and CH3; dmpz = 3,5-dimethylpyrazolate) and the copper(II) complexes [Cu(4-Xdmpz)2]x have been synthesized and characterized. Qualitative solubility, infrared spectroscopic, and differential scanning calorimetric studies are reported for all complexes. Mass spectra support trimeric formulations for the copper(I) complexes. Scanning electron micrographs and powder X-ray diffractograms have been recorded for the copper(II) compounds. Electronic and EPR spectroscopic studies as well as magnetic susceptibility studies from 2 to 300 K are also reported for the copper(II) compounds, which are proposed to have polymeric chain structures. The magnetic data reveal strong antiferromagnetic interactions in all four of the copper(II) compounds. The data have been analysed employing an isotropic Heisenberg model for antiferromagnetic coupling in extended chain polymers. Values of the exchange coupling constant, J, are determined as −58, −61, −66, and −66 cm−1 for the X = H, CH3, Cl, and Br complexes respectively. The X = Cl compound exhibits an abrupt decrease in magnetic susceptibility below 40 K and possible causes of this anomalous behaviour are discussed.

Structural Characterization of Two Crystalline Forms of Bis[2-(1,5-dimethyltrazol-3-yl)-1,10-phenanthroline]-iron(II) Perchlorate—a Spin Crossover System

1996 ◽  
Vol 49 (4) ◽  
pp. 497 ◽  
Author(s):  
KH Sugiyarto ◽  
DC Craig ◽  
HA Goodwin
Keyword(s):  
Room Temperature ◽  
Singlet State ◽  
Crystal Packing ◽  
Bulk Sample ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Quintet State ◽  
Crystalline Forms

At room temperature bis [2-(1,5-dimethyltriazol-3-yl)-1,10-phenanthroline]iron(II) perchlorate has magnetic and Mossbauer spectral properties which indicate that it contains both singlet and quintet state iron(II) in a ratio of approximately 1:2. Two polymorphs were identified in a small batch of crystals grown from acetone/ethanol for crystal structure determination. In polymorph 1 the average iron-nitrogen distance (1.97 Ǻ) is close to the value usually obtained for purely singlet state iron(II) in an [FeN6]2+ system, whereas that for polymorph 2 (2.09 Ǻ) is consistent with the 1:2 ratio of singlet-to-quintet state species. The Mossbauer spectrum of the crystallographic sample is virtually identical to that of the bulk sample. There are small differences in the coordination sphere which could account for the different extent of stabilization of the singlet state in the two polymorphs. The crystal packing differs markedly for the two polymorphs but reveals no obvious rationalization for the spin-state differences. Bis [2-(1,5-dimethyltriazol-3-yl)-1,10-phenanthroline]iron(II) perchlorate , two-thirds water (polymorph 1): monoclinic, space group P 21/c, a 10.766(3), b 25.806(3), c 12.491(4) Ǻ, β 91.17(1)°, Z 4. Bis [2-(1,5-dimethyltriazol-3-yl)-1,10-phenanthroline]iron(II) perchlorate monohydrate (polymorph 2): orthorhombic, space group Pbca, a 16.687(4), b 12.272(2), c 34.305(8) Ǻ, Z 8.

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model to Improve Density Function Calculations

2019 ◽  
Author(s):  
Xianghai Sheng ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Density Functional Theory ◽  
Exchange Coupling ◽  
Density Functional ◽  
Spin Crossover ◽  
Coupling Constants ◽  
Spin Projection ◽  
Coupling Constant ◽  
Projection Model ◽  
Functional Theory

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of J-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Project model provides an affordable and practical approach for effectively correcting spin-contamination errors in molecular exchange coupling constant and spin crossover gap calculations.

Crystal structure determination of the conformation of two bicyclo[3.3.1]nonan-ones

1985 ◽  
Vol 63 (6) ◽  
pp. 1166-1169 ◽  
Author(s):  
John F. Richardson ◽  
Ted S. Sorensen
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Molecular Structures ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Final Agreement

The molecular structures of exo-7-methylbicyclo[3.3.1]nonan-3-one, 3, and the endo-7-methyl isomer, 4, have been determined using X-ray-diffraction techniques. Compound 3 crystallizes in the space group [Formula: see text] with a = 15.115(1), c = 7.677(2) Å, and Z = 8 while 4 crystallizes in the space group P21 with a = 6.446(1), b = 7.831(1), c = 8.414(2) Å, β = 94.42(2)°, and Z = 2. The structures were solved by direct methods and refined to final agreement factors of R = 0.041 and R = 0.034 for 3 and 4 respectively. Compound 3 exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in 4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

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