Metal-nitroxyl interactions. 37. Single-crystal EPR spectra of a spin-labeled copper complex containing an imine-urea linkage (original) (raw)
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J Am Chem Soc, 1979
Resolved electron-electron coupling is observed in the room temperature solution EPR spectra of the spin-labeled copper complex (3-(N-(3-2,2,5,5-tetramethylpyrroline-1 -oxyl)amido)-4,9-dimethyl-5,8-diazadodeca-4,8-diene-2,11 -dione)copper(l1). Values of the coupling constant at room temperature vary with solvent (toluene, CH2C12, THF, 1: 1 THF-CH2Cl2, CHC13, pyridine, MeZSO, 1:l toluene-acetone, and 1O:l toluene-THF), ranging from 475 G (0.0454 cm-I) in T H F to 520 G (0.0496 cm-l) in Me2SO. The coupling constant is also temperature dependent with values changing from 525 G (0.050l cm-I) at -20 OC to 472 G (0.0451 cm-]) at 119 " C in toluene solution.
Polyhedron, 2013
In order to investigate the influence of intermolecular hydrogen bonds and the co-ligands [WS 4 ] 2À and Imt on the structures of copper complexes, two new compounds, [WS 4 Cu 3 I(tdmpp)] 4 Á2CH 3 CN (1) and [CuCl(Imt)Á0.5tdmpp] 2 Á2(CH 3) 2 CO (2), have been synthesized in one pot reactions. The reaction of CuI and (NH 4) 2 WS 4 with tdmpp (1,1,3,3-tetrakis(3,5-dimethyl-1-pyrazole)propane) (molar ratio = 3:1:1) in DMF/CH 3 CN (1:4; v/v) led to the formation of complex 1, while treatment of Imt (imidazolidine-2-thione) and CuCl with tdmpp (molar ratio = 2:2:1) in acetone formed complex 2. These complexes have been structurally characterized by X-ray crystallography, infrared spectroscopy and elemental analyses. Thermal analysis and UV-Vis spectroscopic analysis of complex 1 have also been undertaken. Complex 1 has a tetrameric structure which forms intermolecular C-HÁ Á ÁS and C-HÁ Á ÁI hydrogen bonds, resulting in a 2D polymeric structure. In this complex, the copper(I) atoms have two different geometries: trigonal planar (CuS 2 I) and distorted tetrahedral (CuS 2 N 2). In contrast, complex 2 has a dimeric structure in which the copper atoms are four-coordinate with a distorted tetrahedral CuN 2 SCl geometry. The dimeric molecules link to the oxygen atoms of uncoordinated acetone molecules through N-HÁ Á ÁO hydrogen bonds.
Metal-nitroxyl interactions VI. Analysis of EPR spectra of spin-labeled copper complexes
Journal of Magnetic Resonance (1969), 1978
Spin-spin splittings are analyzed for two nonequivalent electron spins. The resulting equations are applied to the simulation of the EPR spectra of spin-labeled copper complexes exhibiting electron-electron coupling. The electron-electron coupling and z components of the electron-nuclear couplings are treated exactly. The off-diagonal (x, y) components due to electron-copper nuclear coupling are treated as a perturbation, to second order for the transition energies and first order for the transition probabilities. The field dependence of the energy separation, (g,-g,)pH, for the two electron spins is included. Calculated and observed spectra for a spin-labeled derivative of copper(H) bis(acetylacetonato)ethylenediamine are in good agreement.
Metal-nitroxyl interactions. 29. EPR studies of spin-labeled copper complexes in frozen solution
Journal of Magnetic Resonance (1969), 1983
Frozen solution EPR spectra have been obtained for 12 spin-labeled copper complexes. A perturbation calculation including both exchange and dipolar interaction was used to simulate the spectra. The distances between the two spins ranged from 7.5 to 13.5 A. The absolute value of the electron-electron exchange coupling constant ranged from 0 to about 2000 X 1O-4 cm-'.
Inorganic Chemistry, 1996
2-(3-Pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy, IM-3Py (1), reacts with copper(II) bis-(hexafluoroacetylacetonate), Cu(hfac) 2 , to give three complexes. One of them is a centrosymmetric three-spin species, Cu(hfac) 2 (IM-3Py) 2 (4), where two nitroxide ligands are pyridyl bound to the metal and the spins independent from 300 to 5 K. The two other complexes, [Cu(hfac) 2 ] 4 (IM-3Py) 2 (R-phases, 5, and-phases, 6) are six-spin clusters comprising four copper(II) ions linked by two tridentate IM-3Py units. Their molecular structures are almost identical, but they crystallize in different space groups. For both complexes, two octahedral endo metal ions are involved in a cyclic structure and the two others are exocyclic in a trigonal-bipyramidal environment. On the one hand, the magnetic properties of these two clusters are similar since, for both, the high-temperature behavior can only be accounted for by large ferromagnetic interactions; on the other hand they are dramatically different because the R-phase has a S) 3 ground spin state, while the-phase exhibits two transitions resulting in two independent spins below 70 K. The transition temperatures are T C1v) 211 K, T C1V) 152 K, T C2v) 80 K, and T C2V) 70 K. With the help of ab initio calculations on model fragments, the presence of a ferromagnetic interaction through the pyridyl ring has been tentatively rationalized invoking McConnell's electron transfer mechanism. The high-temperature transition has been assigned to a change of the N-imino coordination from equatorial in a trigonal-pyramidal coordination to axial in a square-planar pyramidal environment at the exocyclic copper center. The low-temperature transition corresponds to a switch from axial to equatorial of the nitroxyl coordination at the endocyclic octahedral metal ion. Relevant crystallographic parameters are as follows: 4, triclinic, P1 h, a (Å)) 6.955(2), b (Å)) 11.485(2), c (Å)) 14.012(3), R (deg)) 112.55(1), (deg)) 98.79(1), γ (deg)) 90.28(1), Z) 1; 5, monoclinic, C2/c, a (Å)) 25.319(4), b (Å)) 17.653(3), c (Å)) 19.973(4), (deg))96.60(2), Z) 4; 6, triclinic, P1 h, a (Å)) 12.200(2), b (Å)) 13.389(3), c (Å)) 15.457(3), R (deg)) 102.54(2), (deg)) 110.16(2), γ (deg)) 92.57(2), Z) 1.
Russian Journal of Coordination Chemistry, 2014
A tetranuclear copper(II) complex based on azomethine, which is the condensation product of 1 phenyl 3 methyl 4 formylpyrazol 5 one with 1,3 diaminopropan 2 ol, is synthesized. The complex includes two different tetranuclear clusters: symmetrical and unsymmetrical. They have a pseudo cubane structure and are in a ratio of 1 : 2. The quantum chemical calculation shows that the "unsymmetrical" con former does not correspond to the local minimum on the molecular potential energy surface. Its existence is thus determined by the crystalline packing effects. According to the results of measurements of the tempera ture dependence of the magnetic susceptibility, the ground spin state is a singlet caused by the overall antifer romagnetic interaction between the copper ions. Accepting the molar magnetic susceptibility of the complex to be equal to the sum of susceptibilities of the "symmetrical" and "unsymmetrical" clusters and assuming that the spin Hamiltonian for both clusters includes three exchange parameters, the temperature dependence of the magnetic susceptibility of the complex is satisfactorily described with the following parameters of the model: J 1A = -178, J 2A = 80, J 3A = 18, J 1B = -26, J 2B = -74, J 3B = 46 cm -1 , g A = g B = 2.05.
Inorganic Chemistry, 2015
Solid-state stereochemistry and mobility of paramagnetic copper(II) complexes formed by aliphatic amino acids (L-alanine, D,L-alanine, 1-amino-2-methyl-alanine) and 1-amino(cyclo)alkane-1-carboxylic acids (alkane = propane, butane, pentane, hexane) as bidentate ligands has been studied by 13 C and 2 H solid-state fast magic angle spinning (MAS) NMR spectroscopy. We examined the prospective method to characterize solid-state paramagnetic compounds in a routine way. Both 13 C and 2 H MAS spectra can distinguish D,L and L,L diastereomers of natural and polydeuterated bis([D n ]alaninato)copper(II) (n = 0, 2, 8) complexes with axial and/or equatorial methyl positions (conformations) primarily due to different Fermi-contact (FC) contributions. The three-bond hyperfine couplings clearly show Karplus-like dependence on the torsional angles which turned out to be a useful assignment aid. Density functional theory calculations of the FC term and crystal structures were also used to aid the final assignments. The correlations obtained for bis(alaninato-κ 2 N,O)copper(II) complexes were successfully used to characterize other complexes. The usefulness of the 2 H MAS spectra of the deuterated complexes was underlined. Even the spectra of the easily exchangeable amine protons contained essential stereochemical information. In the case of a dimer structure of bis(1-aminohexane-1-carboxylato-κ 2 N,O)copper(II) both the 13 C and 2 H resolutions were good enough to confirm the presence of the cis and trans forms in the asymmetric unit. With regard to the internal solid-state motions in the crystal lattice, the obtained quadrupolar tensor parameters were similar for the D,L-and L,Lalaninato isomers and also for the cis−trans forms suggesting similar crystal packing effects, static amine deuterons involved in hydrogen bonding, and fast rotating methyl groups.