Weak ferromagnetic behavior, crystal structure, and electronic studies of novel [Cu(II)(Br)(PhCO2)(Sp)] (Sp=(−)-sparteine) complex (original) (raw)
Related papers
Journal of Molecular Structure, 2003
[((−)-Sparteine)(PhCO2)(Cl)]Cu(II) 1 complex is obtained by direct synthesis using copper(0). 1 crystallizes in the monoclinic space group P21 with a=14.7355(12), b=8.9768(5), β=111.916(5)°, and Z=4. The electronic spectrum of 1 shows a broad band with characteristic of a low symmetry and tetragonally distorted square pyramidal local Cu geometry. The far IR spectrum of 1 shows characteristic vibrations of Cu–Cl (260, 267 cm−1), Cu–N (436, 467 cm−1) and Cu–O (457 cm−1) bonds. The 1H NMR spectrum of 1 is typical of magnetic Cu(II) complexes with line broadening due to efficient nuclear relaxation from the metal center. ESR spectra of polycrystalline 1 at 77 K show an axial spectrum with linewidth of 58.6 G and at 300 K of 89.0 G, with areas in the ratio A77/A300=2.79, indicative of antiferromagnetic order. The linewidth is reduced by 34% on going from 300 to 77 K. Standard magnetization measurements at low temperatures show an Curie–Weiss behavior with suggesting a weak exchange coupling interaction. The crystalline structure of 1 shows that the lattice is arranged so that the space between molecules is smaller than 40 Å3, not enough to accommodate solvent molecules. However, the shortest Cu–Cu contact is 7.5912(8) Å.
Probing the Origin of Ferro-/Antiferromagnetic Exchange Interactions in Cu(II)–4f Complexes
Inorganic Chemistry, 2022
The mechanistic investigations between Cu(II) and the anisotropic lanthanides (Ln(III)) are not much explored to date. This is due to the complicated energy spectrum which arises due to the orbital angular momentum of anisotropic lanthanides. Interestingly, the exchange coupling J in Ln(III)−Cu(II) systems was found to be antiferromagnetic for <4f 7 metal ions and ferromagnetic for ≥4f 7 metal ions, while the net magnitude of J Total strength gradually decreases moving from f 1 to f 13. While this is established in several examples, the reason for this intriguing trend is not rationalized. In this article, we have taken up these challenging tasks by synthesizing a family of complexes with the general molecular formula [Cu 2 Ln(HL) 4 (NO 3)](NO 3) 2 , where Ln = La (1-La), Ce (2-Ce), Pr (3-Pr), Gd (4-Gd), Tb (5-Tb), Dy (6-Dy), and Ho (7-Ho) and HL = C 15 H 15 N 1 O 3 ; (2methoxy-6-[(E)-2′-hydroxymethyl-phenyliminomethyl]-phenolate) is a monodeprotonated tridentate Schiff base ligand. Detailed dc magnetic susceptibility measurements performed for all the complexes reveal that the Cu(II) ion is coupled ferromagnetically to the respective Ln(III) ion, which has more than seven electrons in the 4f shell, while an antiferromagnetic coupling is witnessed if Ln(III) has less than seven electrons. The strength of the exchange coupling constant was quantitatively determined for representative complexes from the high-field/high-frequency electron paramagnetic resonance spectroscopy which follows the order of 4-Gd (1.50(10) cm −1) > 5-Tb (1.18(10) cm −1) > 6-Dy (0.56(10) cm −1 based on the − •
Polyhedron, 2019
The pyrimidinyl hydrazone ligand O=C{NHN=C(Me)(pm)} 2 (pm = 2-pyrimidinyl) (L 3 H 2) has two potentially protic H atoms and multiple donor atoms. The reaction of L 3 H 2 with CuCl 2 •2H 2 O yielded the tetranuclear complex [Cu 4 (L 3 H) 2 Cl 6 (CH 3 OH) 2 ] (1). Structural studies on 1 reveal the molecule is located about a crystallographic inversion centre, affording two crystallographically independent Cu(II) centres with the two symmetry equivalent [Cu 2 (L 3 H)Cl 3 CH 3 OH] units connected via µ 2-Cl bridges to generate a linear tetranuclear copper complex. The ligand is singly deprotonated (L 3 H −) and twisted around the diazine N-N´ bond, affording an N 3 donor set for the Cu1 centre and an N 2 O donor set for the Cu2 centre. The Cu1 ion is five coordinate with an [N 3 ] donor set from the L 3 H − ligand and the remaining two sites occupied by Clanions. The Cu2 ion is six coordinate with the L 3 H − ligand offering a mer [N 2 O] donor set, with the three remaining sites occupied by two Cl − anions and a MeOH molecule. Magnetic studies reveal the presence of strong antiferromagnetic interactions via the diazine bridge linking the Cu1 and Cu2 ions and moderate ferromagnetic interactions via the chloro bridges located about the inversion centre, connecting the Cu2 and Cu2i ions.
Inorganica Chimica Acta, 1993
The synthesis, crystal structure and magnetic properties are reported for the trinuclear compound [Cu(H,0),{Cu(HL)(H,0)(C104)}~][C10,],~2H,0, where HL is the monodeprotonated form of 6-methylamino-1,3dimethyl-5-[(2'-carboxyphenyl)azo]uracil. The compound crystallizes in the triclinic system, space group Pl, with cell constants a = 7.824(3), 6 = 12.278(3), c = 13.705(9) A, (Y= 104.34(3), /3=91.80(3), y= 103.37(5)" and Z= 1. The structure was solved and refined to R = 0.071 (R,=O.O64). The structure consists of trinuclear [Cu(H,O),{Cu(HL)(H,O)(CIO,)},lZ+ cations, non-coordinated perchlorate anions and crystal water molecules, held together by a network of hydrogen bonds. The central copper is in an elongated octahedral CuO, chromophore and the terminal copper atoms in distorted square-pyramtdal CuNO, chromophores. Adjacent copper atoms are linked by carboxylate groups in a syn-anti conformation. From the magnetic susceptibility measurements, the complex is found to exhibit weak ferromagnetic interaction between nearest-neighbour copper(I1) ions. The magnitude and nature of the exchange coupling are discussed on the basis of the structural data.
New Journal of Chemistry, 2021
Copper(II) coordination compounds with the condensation product of the diacetylmonoxime and 2-hydrazino-4,6-dimethylpirimidine (H2L) with composition [Сu(Н2L)Br2]·Н2О (I) and [Сu(Н2L)Cl2] (II) were synthesized. Molecular structures of the compounds were established with the help of single crystal X-ray diffraction study. In case of (I) H2O molecules facilitate formation of the infinite intermolecular hydrogen bond (HB) network, leading to ferromagnetic type exchange interaction between copper(II) ions of mononuclear coordination units and antiferromagnetic molecular field (2J = +5.53 cm–1, zJ´ = –0.53 cm–1). At the same time in (II) –(О–H)oxime···Сl centrosymmetric hydrogen bonded dimers are formed from mononuclear coordination units, resulting in presence of antiferromagnetic exchange interaction between Cu(II) centers and molecular field interaction of ferromagnetic type (2J = -2.21 cm–1, zJ´ = +0.63 cm–1). DFT-BS calculations were employed to clarify the nature of the pairwise ex...
Arkivoc, 2007
Cu II (L)(Cl)(L´)]•H 2 O 1 (L = 2-aminomethylbenzimidazole, L´ = L-isoleucinate) compound crystallizes in the orthorhombic space group P2 1 2 1 2 1. A short Cu-O...Cu contact is observed between neighboring molecules in the crystal structure, with a O...Cu separation of 4.214(3) Ǻ. Molecular structure of 1 shows that L and L´ act as bidentate ligands, forming the base of the square pyramidal geometry environment of the Cu II ion, while the chloro is the fifth apical ligand. UV/VIS spectrum of 1 shows d-d transitions with λ max = 603 nm, characteristic of a low symmetry. Far IR spectrum shows ν Cu-N at 493, 404 cm-1 , ν Cu-O at 446 cm-1 , and at 302 cm-1 ν Cu-Cl. ESR X-band of polycrystalline 1 at 77, 300 K show axial spectra with the ratio A 77 /A 300 = 4.51, and a linewidth increase by 14.5 % on going from 300 K to 77 K, suggesting a incipient ferromagnetic exchange interaction. ESR axial spectrum of 1 in solution shows abundant hfs and shfc interactions. Susceptibility vs Temperature data measured from 2-300 K range, show that the magnetic ordering may be due to Cu ions linking by oxygen bridges given place to a weak ferromagnetic interaction. The very weak exchange interaction, J = 0.103 cm-1 , is in agreement with the ESR spectra results and with a Cu II-O...Cu II direct interaction.
Inorganic Chemistry, 2005
The new tetranuclear carbonate complex [Cu 2 L) 2 (CO 3)]‚8H 2 O (1‚8H 2 O) (H 3 L) (2-(2-hydroxyphenyl)-1,3-bis[4-(2hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) has been obtained by two different synthetic routes and fully characterized. Recrystallization of 1‚8H 2 O in methanol yields single crystals of {[(Cu 2 L) 2 (CO 3)]} 2 ‚12H 2 O (1‚6H 2 O), suitable for X-ray diffraction studies. The crystal structure of 1‚6H 2 O shows two crystallographically different tetranuclear molecules in the asymmetric unit, 1a and 1b. Both molecules can be understood as self-assembled from two dinuclear [Cu 2 L] + cations, joined by a µ 4-η 2 :η 1 :η 1 carbonate ligand. The copper atoms of each crystallographically different [(Cu 2 L) 2 (CO 3)] molecule present miscellaneous coordination polyhedra: in both 1a and 1b, two metal centers are in square pyramidal environments, one displays a square planar chromophore and the other one has a geometry that can be considered as an intermediate between square pyramid and trigonal bipyramid. Magnetic studies reveal net intramolecular ferromagnetic coupling between the metal atoms. Density functional calculations allow the assignment of the different magnetic coupling constants and explain the unexpected ferromagnetic behavior, because of the presence of an unusual NCN bridging moiety and countercomplementarity of the phenoxo (or carbonate) and NCN bridges.
ChemistrySelect, 2017
Two novel tetranuclear Cu(II) complexes [Cu4(L 1)4]·3(H2O) (1) and [Cu4(H2L 2)4(H2O)4] (2) (H2L 1 = (E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol; H4L 2 = 2-((2-hydroxy-3methoxybenzylidene)amino)-2-hydroxymethylpropane-1,3-diol) were synthesized from the selfassembly of copper(II) perchlorate and the tridentate Schiff base ligands. Both complexes crystallize in the tetragonal system with space group I 41/a and form tetranuclear species with closed-cubane like core framework. Both the complexes possess a S4 axis but of different stereochemistry due to the different arrangement of the ligands about the copper ions. Variable temperature magnetic susceptibility measurements indicate an overall weak antiferromagnetic exchange coupling in 1, while ferromagnetic exchange coupling in 2. In agreement with their closed-cubane structure, the magnetic behavior of the two complexes have been studied by employing the isotropic spin Hamiltonian of type H = J1 (S1S3 + S1S4 + S2S3 + S2S4)-J2 (S1S2 + S3S4) (J1 describes the magnetic exchange coupling between the four Cu(II) pairs with short Cu•••Cu distances, while J2 characterizes the magnetic exchange coupling between the remaining two intermetallic pairs with long distances). The PHI program was used to study their magnetic behavior. A good agreement between the experimental and fitted curves was found with the following parameters: g = 2.14, J1 =-20.3 cm-1 and J2 = 0 cm-1 for 1 and g = 2.10, J1 = 101.1 cm-1 and J2 =-51.5 cm-1 for 2.