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Two isotypic mononuclear discrete complexes [Co(MeCN)4(tcp)2]·2MeCN (1) and [Ni(MeCN)4(tcp)2]·2MeCN (2) containing the tetracyanopyrrolide anion [C4(CN)4N]– (tcp) were synthesized from [Me4N]tcp and the respective metal perchlorates in acetone/acetonitrile. Tcp coordinates to the transition metal atoms in η1 fashion via the nitrogen atom of the pyrrole ring. No coordination via the cyano groups is observed. Both complexes show nearly ideal paramagnetic behavior according to the Curie law with magnetic moments of 4.98 μB for 1 and 3.09 μB for 2. In the presence of Cu2+ ions tcp reacts with traces of water under hydrolysis of one cyano group to tricyanopyrrole-2-carboxamide (NC4(CN)3C(O)NH2)– (tcpc). From solutions in DMF the complex [Cu(tcpc)2(DMF)2] (3) is isolated.

Purpose The assessment of iron content in brain white matter (WM) is of high importance for studying neurodegenerative diseases. While R2* mapping and quantitative susceptibility mapping is suitable for iron mapping in gray matter, iron mapping in WM still remains an unsolved problem. We propose a new approach for iron mapping, independent of diamagnetic contributions of myelin by assessing the temperature dependency of the paramagnetic susceptibility. Theory and Methods We used unfixed human brain slices for relaxometry and calculated R2′ as a measure for microscopic susceptibility variations at several temperatures (4°C–37°C) at 3 Tesla. The temperature coefficient of R2′ (TcR2p) was calculated by linear regression and related to the iron concentration found by subsequent superconducting quantum interference device (SQUID) magnetometry and by inductively coupled plasma mass spectrometry. Results In line with SQUID measurements, R2′ mapping showed a linear temperature dependency of the bulk susceptibility with the highest slope in gray matter. Even in WM, TcR2p yielded a high linear correlation with the absolute iron concentration. Conclusion According to Curie's law, only paramagnetic matter exhibits a temperature dependency while the diamagnetism shows no effect. We have demonstrated that the temperature coefficient (TcR2p) can be used as a measure of the paramagnetic susceptibility despite of an unknown diamagnetic background. Magn Reson Med 73:1282–1288, 2015. © 2014 Wiley Periodicals, Inc.

The structure and electronic and magnetic properties of LaxSr2–xCrWO6 (x = 0.0, 0.5, 1.0, 1.5, 2.0) were investigated by using the density functional theory. With the increase of La doping, the extra electrons are injected into W 5d orbitals, which makes the spin moments of W increase. In addition, the calculated Curie temperature and total magnetic moments decrease with the increase of the electron doping, in agreement with the experimental observation. This also means that the decrease of Curie temperature with the electron doping is intrinsic. Half metallic properties are obtained for x = 0.0, 0.5, 1.5, and 2.0, whereas for x = 1.0, the compound is semiconducting. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011

Doping of TAGS-85 with 1 at% Ce or Yb forms a dilute magnetic semiconductor system with non-interacting localized magnetic moments that obey the Curie law. X-ray diffraction patterns and slight broadening in 125Te NMR, attributed to paramagnetic effects, suggest that Ce and Yb atoms are incorporated into the lattice. 125Te NMR spin-lattice relaxation and Hall effect show similar hole concentrations of ≈1021 cm−3. At 700 K, the electric conductivity of the Ce- and Yb-doped samples is similar to that of neat TAGS-85, while the thermal conductivity and the Seebeck coefficient are larger by 6% and 16%, respectively. Possible mechanisms responsible for the observed increase in thermopower may include i) formation of resonance states near the Fermi level and ii) carrier scattering by lattice distortions and/or by paramagnetic ions. Due to the increase in the Seebeck coefficient up to 205 μV K−1, the thermoelectric power factor of Ce- and Yb-doped samples reaches 36 μW cm−1 K−2, which is larger than that measured for neat TAGS-85, 27 μW cm−1 K−2. The increase in the Seebeck coefficient overcomes the increase in the thermal conductivity, resulting in a total increase of the figure of merit by ≈25% at 700 K compared to that observed for neat TAGS-85.

The recognition properties of cucurbit[8]uril (CB8) toward nitronyl nitroxide 2-(2-benzimidazolyl)-4,4,5,5-tetramethylimidazolidinyl-3-oxide-1-oxy (1) and its hydrochloride have been investigated. 1•HCl led to 1:1 inclusion complex [1•HCl@CB8], which was characterized both in solution and by single-crystal X-ray diffraction. In this compound only the tetramethylimidazolidinyl fragment is included in the host. The magnetic behavior of the complex corresponds to a Curie law with a large separation of the spin carriers in the solid. In contrast, an insoluble species exhibiting ferromagnetic behavior is formed when pure 1 reacts with acid-free CB8. The formula [(1) 2 @(CB8) 3 ], in which two radical guests are arranged in such a way that the phenyl groups of the benzimidazolyl substituents are both stacked into one CB8 and the tetramethyl fragments are each capped by a terminal macrocycle, is proposed, in agreement with microanalysis, spectrophotometric, EPR, and magnetic measurements. According to McConnell's rules, the alternating spin densities within the stacked aromatic fragments result in a ferromagnetic interaction (J = + 2.3 cm ―1 , H = ―2JS 1 S 2 ) and a triplet ground spin state for the inclusion complex.

International audience; The Cs3Mo6Ii6Ii2−xSeixIa6 series has been obtained by a solid-state route. There is evidence for a solid solution between the compositions Cs3Mo6Ii6Ii0.8Sei1.2Ia6 and Cs3Mo6Ii6Ii0.4Sei1.6Ia6 (space group: Requation imagec, Z=6; a=16.7065(4), c=20.5523(4) Å, V=4967.8(2) Å3 and a=16.6354(3), c=20.5444(4) Å, V=4923.7(2) Å3, respectively). The structure of this new series is based on magnetic [Mo6Ii6Sei2Ia6]3− and diamagnetic [Mo6Ii7SeiIa6]3− units with 23 and 24 valence electrons per Mo6 cluster, respectively. For a particular x, the structure of Cs3Mo6Ii6Ii2−xSexIa6 is based on a mixture of (x−1) [Mo6Ii6Sei2Ia6]3− with (2−x) [Mo6Ii7SeiIa6]3−. This leads to an average [Mo6Ii6Ii2−xSexIa6]3− ionic unit deduced from single-crystal X-ray diffraction investigations. The two inner positions of the average face-capped [Mo6Ii8−xSeixIa6]3− ionic units (located on the threefold axis of the unit) are randomly occupied by iodine and selenium, whereas the other ligand positions are fully occupied by iodine. Low-temperature electron paramagnetic resonance (EPR) studies reveal a signal split into two components with g∥>g⊥. The reciprocal double integration intensity of the EPR signal versus T graph reveals a typical Curie law behavior. A density functional theory (DFT) study indicates that occupation of the inner position on the threefold axis by selenium atoms is preferred energetically among the three possible distributions of selenium atoms. The comparison of experimental and theoretical g values confirms the crystallographic analysis and agrees with the axial elongation of the Mo6 cluster within the crystal structure.

Two-dimensional numerical computations were carried out in order to elucidate the effect of a Kelvin force on the air in two coaxial circular pipes with open ends under both gravitational and nongravitational fields. The outer pipe with open ends corresponds to the bore space of the superconducting magnet. The inner pipe with open ends is assumed to be placed inside this bore space. The sidewall of the outer pipe is cooled isothermally. The central region of the inner pipe is heated isothermally and the other region is thermally insulated. The magnetic gradient that was produced by the electric current circulating within the circular electric coil was applied to air in two coaxial circular pipes with a thermal gradient. Moreover, the present numerical computations were carried out by changing the relative positions of the circular electric coil and the inner pipe. In both gravitational and nongravitational fields, when the circular electric coil was placed at the end of the heated region of the inner pipe, the Kelvin force was produced in the inner pipe and the magnetothermal air jet was created. As a result, the hotter air rapidly flowed out from the end of the inner pipe. These phenomena could be successfully explained by considering the temperature dependence of the mass magnetic susceptibility of air according to Curie's law.

High-temperature treatment of acetonitrile with CaC2 and FeCl2 afforded crystals of the new iron(III) S = 1/2 low-spin complexes [FeL3]ROH (R = CH3 or C2H5), whose crystal structures were determined by single-crystal X-ray structural analysis. The methanol complex consists of a one-dimensional arrangement of the iron moieties, while each methanol molecule is separated from each other by the complexes. On the other hand, the ethanol complex contains a two dimensional arrangement of the iron moieties and one dimensionally aligned ethanol molecules elongated perpendicular to the sheet. Because of the large difference in the inter-complex overlap patterns between the ligands, the two materials show quite different magnetic properties. The magnetism of the crystal containing ethanol is well described by the singlet–triplet model with the antiferromagnetic interaction 2J/kB = –7.5 K, while that containing methanol obeys the Curie law with a negligibly small Weiss temperature.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Phase transition of a self-avoiding walking polymer chain with spatial nearest neighbor ferromagnetic Ising interaction on the simple cubic lattice is investigated using Metropolis dynamic Monte Carlo technique. Magnetic susceptibility χ is determined from the Brillouin function and from the linear response of magnetization to external magnetic field in small field region. We find the later is better, though both are in consistent with each other at high temperatures. The magnetic susceptibility χ can be expressed using the Curie law and thus the Curie temperature θ is estimated. The chain length dependent Curie temperature θ of the chain model can be well fitted as θ = 1.40 − 4.0 × n−0.619 based on the finite-size scaling law. The transition temperature for an infinite long chain θ(∞) = 1.40J/kB and the exponent ϕ = 0.619 are in agreement with our previous study (J Chem Phys 2003, 119, 2439). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 969–973, 2006

Until now, the known structures of heterodinuclear Cu−Ln complexes involve compartmental Schiff-base ligands with saturated diamino chains. We report here two Cu−Ln complexes (Ln = Gd or Ce) which are the first structurally characterized Cu−Ln entities involving S-methylisothiosemicarbazide as the diamino bridge, with open chain and macrocyclic ligands. The macrocyclic Cu−Gd entity is a well isolated dinuclear complex whereas two hydrogen bonds join together a pair of binuclear Cu−Ce complexes to give tetranuclear {Cu−Ce···Ce−Cu} entities. The Cu−Gd complexes [H = -J(SCuSGd)] exhibit ferromagnetic interactions between 5 and 5.5 cm−1. Since the Cu−Ce complexes do not follow the Curie law due to the presence of orbital degeneracy, an analysis based on a simple spin-only Hamiltonian is not possible. Nevertheless, the EPR spectra of the Cu−Ce complexes do confirm the existence of magnetic interactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The semi-metallic cubic compound YBiPt doped by Er 3+ (4f 11 ) has been studied by ESR technique between 4 and 300 K. X-band and Q-band measurements have been performed. The angular dependence of the ESR spectra on the crystal orientation with respect to the static magnetic field has been measured. Two anisotropic lines with hyperfine peaks coming from the interaction between electronic and nuclear spins of 167 Er 3+ (I= 7/2) isotopes have been observed below 30 K in the spectra. Computer modeling showed that these lines are the ESR signals from the quadruplet ground state of Er 3+ ions in the cubic crystal field. The values of crystal field parameters B 4 = -5.68 x 10 -4 cm -1 and B 6 = -6.64 x 10 -6 cm -1 have been extracted. Also an isotropic line near g = 2 have been observed in both frequency bands. Dysonian lineshape of the spectra components due to the skin-depth effect shows the conducting property of the sample under study. The temperature dependence of the spectra intensity obeys the well-known Curie law for paramagnetism arising from the unpaired electrons of Er 3+ ion.

The dependence of the Curie temperature of many ferroelectric perovskite solid solutions on the component concentration is nonlinear. Causes of the nonlinearity (limited solubility of components, ion ordering, influence of the morphotropic phase boundary, diffusion of the ferroelectric phase transition, frustration of the crystal lattice) are discussed practically for the first time. In some cases, it is impossible to explain the nonlinearity without solution of some common problems.

We examine the critical behavior of a finite alternating ferroelectric superlattice based on the transverse Ising model. By the transfer matrix method we derive analytical equations for the Curie temperature of the superlattice. Numerical results are obtained for the dependence of the Curie temperature on the thickness and exchange constants of the superlattice. The effect of transverse field on the Curie temperature is also investigated.

Face-centered cubic and rhombohedral phases of pressure-temperature treated C 60 were investigated by ESR spectroscopy in the 5 to 550 K temperature range. It was found that the ESR spectra of the former differ only slightly from those of the starting C 60 powder. The intensity of the ESR signal from this phase reduces upon heating the specimens above 480 K. In contrast, the rhombohedral phase shows an intense narrow ESR line which obeys the Curie law and does not change much upon heating. The origin of paramagnetic centers in the high-pressure phases of C 60 and their relationship to the structure of the substances are discussed.

A series of m,n′-diazidodiphenyl ethers (m ≤ n, m = 3,4; n = 3,4) was photolyzed at 77 K in frozen, glassy 2-methyltetrahydrofuran matrices to generate the corresponding diphenyl ether m,n′-dinitrenes for study by electron spin resonance (ESR) spectroscopy. 3,4′-Diazidodiphenyl ether gave an ESR spectrum dominated by a mononitrene peak with ∣D/hc∣ = 0·972 cm−1, and also showed a weak dinitrene quintet spectrum with ∣D/hc∣ = 0·162 cm−1 having ESR spectral intensity vs temperature dependence (Curie law) consistent with either a high-spin ground state or a very small singlet–quintet gap. Di(3-azidophenyl) ether gave a strong mononitrene peak with ∣D/hc∣ = 0·996 cm−1 and a quintet dinitrene ESR spectrum (∣D/hc∣ = 0·162 cm−1) which exhibited non-linear Curie law intensity behavior consistent with the quintet being a thermally populated excited state 40 cal mol−1 above a singlet ground state. Di(4-azidophenyl) ether gave a strong mononitrene peak with ∣D/hc∣ = 0·961 cm−1, but no observable spectrum related to a high-spin open-shell dinitrene. The results are consistent with oxygen being a weak exchange coupling linker in pi-conjugated open-shell molecules. The observed ground-state spin multiplicities are in accord with qualitative superexchange and connectivity models, despite any perturbations due to resonance effects between the oxygen linker and p-nitrene sites.

In photolysis of 4,4′-diazidodiphenyl sulfide quintet ESR peaks were observed and the plots of these signal intensities vs. temperature obeyed the Curie law, although no quintet signals were observed in the photolysis of 4,4′-diazidodiphenyl ether. The ESR spectrum upon the irradiation of 3,4′-diazidodiphenyl sulfide showed quintet resonances of 3,4′-dinitrenodiphenyl sulfide. Both Curie analysis and PM3-CI calculations indicated that the quintet state is a ground-state.

The synthesis, characterization, and physical properties of perchloro-2,6-bis(diphenylmethyl)-pyridine-α,α'-ylene biradical (1) and αH-tricosachloro-2,6-bis(diphenylmethyl)pyridine-α'-yl radical (2) which present exceptionally high stabilities are reported. The synthesis of 1 and 2 have been accomplished using different strategies in order to get them separately, although 1 always contains 2 as an impurity. 1 is a molecule constituted by two trivalent carbon atoms linked by a trichlorom-pyridylene spacer which has proved to be a good ferromagnetic coupling unit. Magnetic susceptibility measurements from 4.2 to 300 K show that the ground state of 1 is the triplet being 2J=358±14 cm -1 (1.03 kcal/mol), the triplet-singlet energy gap. At low temperature, an antiferromagnetic interaction between intermolecular spines was observed (Curie temperature, θ 1 =-2.02±0.10K). The EPR spectrum of 1 in frozen 2-methyltetrahydrofuran (133 K) in the Δm s =±1 region affords three symmetric pairs of lines corresponding to a triplet species without axial symmetry with zfs parameters |D/hc|=0.0081 cm -1 . The Δm s =±2 transition follows the Curie law over the range 10.0-62.o K, supporting the highest multiplicity of the molecule in the ground state. The cyclic voltammogramm of 1 exhibits a redox couple (E°=0.18 V vs SCE) which is attributed to the reduction of this biradical to the stable anion 12 (1 - ), and a second irreversible peak (E p c = -0.25 V vs SCE) which is ascribed to the formation of the unstable dianion 13 (1 2- ). The electronic spectrum of 1 is presented and discussed

Using single-crystal and powder X-ray diffraction methods, the crystal structure of Ba 5 Fe 4 Ti 10 O 31 was determined and its magnetic and dielectric properties were measured. Ba 5 Fe 4 Ti 10 O 31 crystallizes in space group P6 3 /mcm (No. 193) ( a =9.9886(2), c =42.226(2) A: Z =6: ρ calc =5.15 g cm −3 ) and exhibits an 18-layer close-packed structure built from vacancy-free [O,(Ba,O)] layers. The structure features octahedral sites occupied by a mixture of Fe 3+ and Ti 4+ , with some preferential ordering, and tetrahedral sites occupied by Fe 3+ , one of which shares faces and is half occupied. Some Ba ions in the structure display (9+3) coordination with three unusually long Ba–O bond distances. Computation of bond valence sums about the cation sites using the observed bond distances reveals significant deviations from the valence sum rule, indicating that the structure of Ba 5 Fe 4 Ti 10 O 31 contains residual strain not relieved by distortion. Indexed experimental X-ray powder diffraction data for Ba 5 Fe 4 Ti 10 O 31 are given and are in excellent agreement with those calculated from the results of the single-crystal structure determination. The compound exhibits approximately paramagnetic behavior that deviates somewhat from the Curie Law. Application of this formalism to the 1/ χ vs. T data above 250 K yields an effective moment consistent with the presence of high-spin Fe 3+ ( S =5/2), and a negative Weiss constant (≈−190 K) indicating cooperative magnetic interactions that are overall antiferromagnetic. The relative permittivity and dielectric loss tangent of a sintered polycrystalline disk of Ba 5 Fe 4 Ti 10 O 31 were measured between 7.1 and 7.7 GHz, yielding values (corrected for theoretical density) of 32 and 3.3(±0.3)×10 −3 , respectively, that were essentially independent of frequency.

Synthesis of poly(4′-vinyl-2,4,6-tri-tert-butyl-diphenyloxalate) and its 65 : 35 and 19 : 81 copolymers with styrene are described. Rigid phase broad-band photolysis of the homopolymer with a quartz filtered xenon arc at 77 K results in production of up to 25% of the theoretical number of spins/mol expected for quantitative production of pendant phenoxyl radicals, and shows no major loss of radical signal in the ESR at temperatures below 100 K. Curie law analysis of the temperature dependence of the ESR radical signal intensity for the neat photolyzed homopolymer 1 shows curvature consistent with antiferromagnetic pairing of radical spins at low temperatures. Since through-bond conjugation of radical spins is not possible in this system, the antiferromagnetic interaction is interpreted in terms of intrachain and/or interchain through-space exchange interactions.

A simple model is presented as the basis for explaining the equations that describe the isotropic shift for paramagnetic molecules in solution. The simplest case is that of an axially symmetric molecule for which the Curie Law is valid and for which zero field splitting and second-order Zeeman effects are small. It is used as a point of departure for considering the many underlying factors that affect observation of NMR resonances in paramagnetic molecules.

The static dielectric constant ϵs in Pb1−xSnxTe (x = 0 to 0.4) single crystals is determined from a magnetoplasma reflection measurement between 4.2 and 100 K. At high temperatures ϵs increases with increasing temperature obeying a Curie law. The Curie constant is practically unchanged for different alloy composition, and the inverse static dielectric constant at 4.2 K decreases lineaarly with x, going to zero at alloy composition x = 0.35. At x = 0.40, a phase transition is observed at 20 K. The temperature dependence of ϵs is explained by anharmonic terms of lattice vibrations. La constant dielectrique ϵs dans les monocristals Pb1−xSnxTe (x = 0 to 0,4) a ete determine par la mesure de reflexion de magneto-plasma a temperatures entre 4,2 et 100 K. A hautes temperatures, ϵs augmentes avec temperature par la loi de Curie. Les constantes de Curie dans alliage compositions differentes ne different pas de l'un l'autre, et 1/ϵs a 4,2 K diminuent en ligne directe avec x et vont a zero a alliage compositions x = 0,35. A x = 0,40, la transition de phase est trouve a 20 K. La dependence de temperature de ϵs est explique par le terme de anharmonique de vibration de reseau.

A systematical study of electrical conductivity and EPR of iodine-doped anthracene polymers (C14H6Ix)n is carried out within a wide range of iodine concentrations (0.07 ≦ x ≦ 0.85). The room temperature electrical conductivity has a broad maximum near x = 0.5. No metallic-type conduction is observed. The intensity of EPR signal for all of the investigated samples depends on temperature according to the Curie law and has a minimum near x = 0.19. A clear decoupling of paramagnetism with iodine concentration and electrical conductivity is detected. An idealized model of the structure of (C14H6Ix)n including polarons and bipolarons is proposed. On the base of the model a mechanism of generation and compensation of spin and charge during the doping process is discussed and an interpretation of experimental data is given. [Russian Text Ignored]

Using an RF-SQUID magnetometer, the temperature-dependent magnetic susceptibility of dilute Pt-Fe alloys containing 10.5 ppm Fe, and 0.87 and 0.99 at% Fe is measured in the temperature range 1 to 4.2 K and in de-fields between 0.5 and 15 Oe. For 10.5 ppm Fe, the susceptibility obeys the Curie law, and the saturation magnetic moment μsat is ≈ 9.3μB/Fe. The Pt-0.87 at% Fe and −0.99 at% Fe alloys are spin-glass and quasiferromagnetic, respectively, and both show superparamagnetic properties at temperatures between transition temperature Tt and ≈ 2Tt. Furthermore, the susceptibility of these alloys, around and below Tt, is field dependent, decreasing in magnitude with increasing field. Die temperaturabhangige magnetische Suszeptibilitat von verdunnten Pt-Fe-Legierungen, die 10,5 ppm Fe, und 0,87 und 0,99 At% Fe enthalten, wird mit Hilfe eines RF-SQUID-Magnetometers im Temperaturbereich von 1 bis 4,2 K und im dc-Feld (Gleichstromfeld) zwischen 0,5 und 15 Oe gemessen. Bei 10,5 ppm Fe folgt die Empfindlichkeit dem Curie-Gesetz; das Sattigungsmoment, μsat betragt ≈ 9,3 μB/Fe. Die Legierungen Pt-0,87 At% Fe und −0,99 At% Fe sind Spinglas bzw. quasiferromagnetisch. Beide Legierungen weisen bei Temperaturen zwischen Tt und ≈ 2Tt superparamagnetische Eigenschaften auf. Auserdem ist die Suszeptibilitat dieser Legierungen um und unterhalb von Tt feldabhangig und nimmt mit steigendem Feld ab.

The ferromagnetic Curie temperature and the paramagnetic Curie temperature in the first and second approximation of iteration are calculated for the layer magnetizations starting from the implicit system of equations given in [1]. The dependence of these Curie temperatures as a function of the number of layers, n, for several lattice structures and surface orientations is discussed. Ausgehend von einem in [1] angegebenen Gleichungssystem zur Bestimmung der Netzebenenmagnetisierungen, werden die ferromagnetische Curietemperatur und die paramagnetische Curietemperatur in erster und zweiter Iterationsnaherung berechnet. Es wird die Abhangigkeit dieser Curietemperaturen von der Anzahl n der Netzebenen fur verschiedene Gittertypen und Oberflachenorientierungen diskutiert.

Two new polynuclear chromium(III) complexes with a bromide bridge have been prepared and characterized. One of them is a dinuclear with two Br − as a bridging ligand; the other is presumably an angular trinuclear with only one Br − as a bridgin ligand between each pair of Cr(III) ions. The complexes were prepared by heating in the solid state the known precursor complexes [CrF 2 (aa)(H 2 0) 2 ] Br (aa=ethylenediamine or 1,2-cyclohexanediamine). By means of TG measurements the kinetic parameters have been calculated for the two processes. The activation energy, E a , is very low in both cases indicating a dissociative mechanism and an open structure in the crystal lattice. The magnetic measurements up to helium liquid temperature indicate a weak antiferromagnetic coupling constant in the trinuclear complex of ethylenediamine hut a Curie law behaviour in the dinuclear compound of 1,2-cyclohexanediamine.

Isotropic paramagnetic proton n.m.r. shifts have been measured for the low-spin title complex in [2H5]pyridine. The temperature dependence of the shifts shows large deviations from the Curie law. The deviation is interpreted in term of the effects of temperature-dependent ligand field on mixing of excited electronic configurations with the ground state. The contact shifts evaluated from the isotropic shifts are shown to arise from spin delocalization through both σ and π orbitals. the latter having a smaller contribution than the former. The pattern of the contact shift is explained by the ground-state configuration of CoII where the unpaired electron is primarily in the dz2 orbital, and by the non-planar structure of the complex.