Strong Antiferromagnetic Spin Coupling Research Articles

Quantum geometric spin frustration of antiferromagnetic CuFeO2 enables photocatalytic applications

Photocatalysis, containing a potential solution to the global crises of energy shortage and the greenhouse effect, has been studied extensively in recent years. The CuFeO2 (abbreviated as CFO) is a material with a Delafossite structure, and has also been widely studied because of its triangular lattice antiferromagnets. The triangular lattice composed of Fe3+ ions, along with strong antiferromagnetic spin coupling between the Fe3+ ions, leads to a geometric spin frustration. Furthermore, CFO is also a potential candidate for the photocatalytic material due to its narrow band gap of 1.1–1.6 eV, electrochemical stability in an aqueous environment, high charge carrier mobility, flat-band potential positioned at ∼ 1 eV, and contains an abundance of raw materials in the earth. In this study, we successfully grew the size and highly-quality CFO single crystals using the optical floating-zone technique. Powder x-ray diffraction (XRD) and Rietveld refinement indicate that the CFO is a rhombohedral structure with a space group of R3̅m, consisting of edge-shared FeO6 octahedron to form the FeO2 layer, and the Cu cations occupied between the two FeO2 layers. The core-level electron energy loss (EEL) spectra found the valence of Fe and Cu in CFO is +3 and +1, respectively. The low-loss EEL spectrum observed two volume plasmons at ∼5 eV and ∼23 eV contributed from the collective oscillation of Cu-O antibonding states σCu−O* and mixed nonbonding Cu 3dxy, σCu−O bonding states, and Fe-O, respectively, based on the density function theory calculation. The optical absorption spectrum measured the energy bandgap for CFO is about 1.5 eV. The Raman spectrum shows significant Eg and A1 g vibration modes corresponding to the in-plane Fe-O and out-of-plane Cu-O vibrations, respectively. Both magnetic susceptibility, χ(T), with the applied magnetic field along the c-axis and specific heat capacity reveal the two magnetic phase transition temperatures at low temperatures: TN1 = 13.5 K when transition from paramagnetic (PM) phase to partially disordered antiferromagnetic, and TN2 = 10.5 K when complete transition from partially disordered antiferromagnetic to antiferromagnetic phase. The additional calculation of magnetic entropy change is 0.15, which is roughly close to 0.2, meaning that only 1/5 of the Fe3+ spins are disordered when transforming from PM states to partially disordered at T < TN1 in this study. The presence of instantaneous ferromagnetic spin arrangement (↑↑↓) extends the residence time of H2O on the surface of CFO, facilitating electron exchange with CFO and promoting photocatalytic water splitting reactions.

Endohedral σ-Diradical Nitrogen-Vacancy Diamond Nanoclusters with a Confined Magnetic Space and Strong Electronic Spin Couplings.

The electronic properties and their modulations for the nitrogen-vacancy (NV) centers in various nanoscale diamonds are of profound current interest because of their potential applications. However, although the NV centers as chromophores in diamond are the most widely studied, surprisingly, little is known about their magnetic spin coupling properties up to now. Here, we for the first time show, using the spin-polarized DFT calculations, that the NV centers can act as unique endohedral σ-diradical magnets in diamond nanoclusters and exhibit quite strong ferromagnetic (FM) or antiferromagnetic (AFM) spin coupling characteristics due to their unique endotetrahedral structures with favorable radical-radical contacts. Although the neutral NV center (NV0) in its doublet ground state exhibits quite strong AFM spin coupling among three radical C-sites (i.e., an AFM triradical center), interestingly, excess electron injection can convert it to a FM diradical magnet (i.e., the triplet ground state NV-) with almost unchanged J-coupling magnitude, and the J-coupling of the nanocluster can be noticeably enhanced by F-termination of the surface due to triradical spin delocalization mediated by excess electron. However, interior modification (one C in the endotetrahedron core is substituted by N or B or is hydrogenated) can assign the nanocluster perfect AFM diradical character. The spin coupling strength presents a quasilinear correlation with the distance between the two C radicals in the NV core for the same size of the clusters and a high linear correlation with the energy difference between two singly occupied molecular orbitals. Clearly, the FM and AFM couplings as well as their switching behavior in such NV defect diamond nanoclusters featuring the endohedral σ-diradicals are a novel type of promising magnetic material motifs. These findings open up promising spintronic application prospects of the NV diamonds and provide helpful information for the design of inorganic magnetic materials and logic devices.

Different types of interactions between fullerene C60 and C70 anions and metal tetraphenylporphyrins in the (PMDAE+)(MIITPP)(Fullerene−)⋅Solvent complexes (M = Co, Mn, Zn) containing coordinating N, N, N, N‘, N‘-pentamethyldiaminoethane cations

Series of anionic salts of fullerenes C60 and C70 with different metal tetraphenylporphyrins, MIITPP, where M = Co, Mn and Zn, and N, N, N, N‘, N‘-pentamethyldiaminoethane cations (PMDAE+) has been obtained in a crystalline form. Composition of the complexes is (PMDAE+)⋅(MIITPP)(C60−)⋅XC6H4Cl2 (M = Co, X = 1.25 (1), M = Mn, X = 0.75 (2) and M = Zn, X = 0.75 (3)) and {(PMDAE+)⋅ZnIITPP}2⋅(C70−)2⋅4C6H4Cl2 (4). Both fullerene anion and nitrogen-containing PMDAE+ cation can coordinate to metal porphyrin competing with each other. Weak Co-C(C60−) coordination bond of 2.426(7) Å length (120 K) is formed in 1 whereas PMDAE+ cation only weakly coordinates to CoIITPP. Dissociation of Co-C(C60−) bond observed at 90–310 K is accompanied by a transition of 1 from singlet to triplet state with an energy gap of 574 ± 3 K. According to the calculations negative charge on C60− is only −0.548 due to electron transfer to the macrocyclic ligand through the cobalt atom. Charge transfer bands are observed in {CoIITPP(C60)}− at 700 and 1240 nm. On the contrary, PMDAE+ cations coordinate to MnIITPP and ZnIITPP in 2 and 3, respectively, with short M−N(PMDAE+) bonds of 2.27–2.33 Å length. In these cases fullerenes are preserved in the non-coordinated radical anion state. Fullerenes are arranged in closely packed π-stacking {C60•−}2 dimers with short interfullerene center-to-center distances of 9.92–9.95 Å. Nevertheless, the C60•− radical anions do not form intercage CC bonds down to 1.9 K. Strong antiferromagnetic coupling of spins is observed in the {C60•−}2 dimers of 3 with exchange interaction of J/kB = -21 K. Both {(PMDAE+)⋅MnIITPP} and C60•− species are paramagnetic in 2 having S = 5/2 and S = 1/2 spin states, respectively. These spins are coupled antiferromagnetically with Weiss temperature of −16 K. It is obvious that magnetic coupling occurs not only in the {C60•−}2 dimers but MnIITPP is also involved in this coupling. The C70•− radical anions are dimerized in 4 forming diamagnetic singly-bonded (C70−)2 dimers which manifest intense NIR absorption. As a result, complex 4 is EPR silent.

Electronic Communication as a Transferable Property of Molecular Bridges?

Electronic communication through molecular bridges is important for different types of experiments, such as single-molecule conductance, electron transfer, superexchange spin coupling, and intramolecular singlet fission. In many instances, the chemical structure of the bridge determines how the two parts it is connecting communicate, and does so in ways that are transferable between these different manifestations (for example, high conductance often correlates with strong antiferromagnetic spin coupling, and low conductance due to destructive quantum interference correlates with ferromagnetic coupling). Defining electronic communication as a transferable property of the bridge can help transfer knowledge between these different areas of research. Examples and limits of such transferability are discussed here, along with some possible directions for future research, such as employing spin-coupled and mixed-valence systems as structurally well-controlled proxies for understanding molecular conductance and for validating first-principles theoretical methodologies, building conceptual understanding for the growing experimental work on intramolecular singlet fission, and developing measures for the transferability of electronic communication as a bridge property.

Fullerene and endometallofullerene Kagome lattices with symmetry-forced spin frustration.

Salts of fullerene C60˙- and endometallofullerene Sc3N@Ih-C80˙- radical anions with Bu3MeP+ cations ((Bu3MeP+)3(C60˙-)3·C6H4Cl2 (1) and (Bu3MeP+)3(Sc3N@Ih-C80˙-)3·C6H4Cl2 (2)) have been obtained. The C3 symmetry of the Bu3MeP+ cation provides 2D Kagome lattices with an equilateral triangle arrangement of fullerenes in accordance with trigonal crystal symmetry P31m. The C60˙- and Sc3N@Ih-C80˙- radical anions preserve their monomeric forms in 1 and 2 with the S = 1/2 spin state down to 1.9 K. The close packing of the fullerene radical anions results in strong antiferromagnetic coupling of the spins with Weiss temperatures of -108 K for 1 and -43 K for 2. Compound 1 is a rare example of a magnetic system in which in spite of the strong magnetic coupling of spins no long-range ordering is observed down to 1.9 K. The 13C NMR spectra of the 13C enriched sample of 1 support the absence of the antiferromagnetic ordering of spins down to 1.5 K. Thus, the crystals of 1 preserve large spin frustration forced by the trigonal symmetry. Therefore, compound 1 is a promising candidate for the first observation of a quantum spin liquid (QSL) state in a fullerene-based system. Isostructural salt 2 is the first compound that contains monomeric paramagnetic Sc3N@Ih-C80˙- radical anions stable down to 1.9 K, which show strong spin frustration. These data indicate the ability of endometallofullerenes to give exotic magnetic systems such as QSLs.

Ferrocene-based diradicals of imino nitroxide, nitronyl nitroxide and verdazyl, and their cations are possible SMM: A quantum chemical study

Six diradicals designed from imino nitroxide, verdazyl and nitronyl nitroxide monoradicals coupled via the ferrocene moiety and six corresponding triradical cations are quantum chemically investigated. The transoid conformation is employed for considerations of general stability. All biradicals are found as very weakly and antiferromagnetically coupled. This agrees with experiment. The cations have strong antiferromagnetic spin-coupling. The charge and spin population distributions, spin alternation pattern, and the disjoint nature of SOMOs can be used to explain the nature and extent of magnetic interaction. Calculated EPR characteristics identify the neutral species as well as their cations as possible single molecule magnets.

Coordination Complexes of Transition Metals (M = Mo, Fe, Rh, and Ru) with Tin(II) Phthalocyanine in Neutral, Monoanionic, and Dianionic States.

The ability of tin atoms to form stable Sn-M bonds with transition metals was used to prepare transition metal complexes with tin(II) phthalocyanine in neutral, monoanionic, and dianionic states. These complexes were obtained via the interactions of [Sn(IV)Cl2Pc(3-)](•-) or [Sn(II)Pc(3-)](•-) radical anions with {Cp*Mo(CO)2}2, {CpFe(CO)2}2, {CpMo(CO)3}2, Fe3(CO)12, {Cp*RhCl2}2, or Ph5CpRu(CO)2Cl. The neutral coordination complexes of Cp*MoBr(CO)2[Sn(II)Pc(2-)]·0.5C6H4Cl2 (1) and CpFe(CO)2[Sn(II)Pc(2-)]·2C6H4Cl2 (2) were obtained from [Sn(IV)Cl2Pc(3-)](•-). On the other hand, the coordination of transition metals to [Sn(II)Pc(3-)](•-) yielded anionic coordination complexes preserving the spin on [Sn(II)Pc(3-)](•-). However, in the case of {cryptand[2,2,2](Na(+))}{CpFe(II)(CO)2[Sn(II)Pc(4-)]}(-)·C6H4Cl2 (4), charge transfer from CpFe(I)(CO)2 to [Sn(II)Pc(3-)](•-) took place to form the diamagnetic [Sn(II)Pc(4-)](2-) dianion and {CpFe(II)(CO)2}(+). The complexes {cryptand[2,2,2](Na(+))}{Fe(CO)4[Sn(II)Pc(3-)](•-)} (5), {cryptand[2,2,2](Na(+))}{CpMo(CO)2[Sn(II)Pc(2-)Sn(II)Pc(3-)(•-)]} (6), and {cryptand[2,2,2](Na(+))}{Cp*RhCl2[Sn(II)Pc(3-)](•-)} (7) have magnetic moments of 1.75, 2.41, and 1.75 μ(B), respectively, owing to the presence of S = 1/2 spins on [Sn(II)Pc(3-)](•-) and CpMo(I)(CO)2 (for 6). In addition, the strong antiferromagnetic coupling of spins with Weiss temperatures of -35.5 -28.6 K was realized between the CpMo(I)(CO)2 and the [Sn(II)Pc(3-)](•-) units in 6 and the π-stacking {Fe(CO)4[Sn(II)Pc(3-)](•-)}2 dimers of 5, respectively. The [Sn(II)Pc(3-)](•-) radical anions substituted the chloride anions in Ph5CpRu(CO)2Cl to form the formally neutral compound {Ph5CpRu(II)(CO)2[Sn(II)Pc(3-)]} (8) in which the negative charge and spin are preserved on [Sn(II)Pc(3-)](•-). The strong antiferromagnetic coupling of spins with a magnetic exchange interaction J/k(B) = -183 K in 8 is explained by the close packing of [Sn(II)Pc(3-)](•-) in the π-stacked {Ph5CpRu(II)(CO)2[Sn(II)Pc(3-)](•-)}2 dimers.

Strong antiferromagnetic coupling of spins in the (MDABCO+)(C60·-) salt with 3D close packing of the C60·- radical anions (MDABCO+: N-methyldiazabicyclooctanium cation).

A new salt, (MDABCO(+))(C60(·-)) (1; MDABCO(+) = N-methyldiazabicyclooctanium cation), was obtained as single crystals. The crystal structure of 1 determined at 250 and 100 K showed 3D close packing of fullerenes with eight fullerene neighbors for each C60(·-). These neighbors are located at 10.01-10.11 Å center-to-center distances (250 K) and van der Waals interfullerene C⋅⋅⋅C contacts are formed with four fullerene neighbors arranged in the bc plane. Fullerene ordering observed below 160 K is accompanied by the appearance of one and a half independent C60(·-) and trebling of the unit cell along the b axis. Fullerenes are packed closer to each other at 100 K. As a result, fullerenes are located in the three-dimensional packing at 9.91-10.12 Å center-to-center distances and 18 short interfullerene C⋅⋅⋅C contacts are formed for each C60(·-). Although they are closed packed, fullerenes are not dimerized down to 1.9 K. Magnetic data indicate strong antiferromagnetic coupling of spins in the 70-300 K range with a Weiss temperature of Θ = -118 K. Magnetic susceptibility shows a round maximum at 46 K. Such behavior can be described well by the Heisenberg model for square two-dimensional antiferromagnetic coupling of spins with an exchange interaction of J/kB = -25.3 K. This magnetic coupling is one of the strongest observed for C60(·-) salts.

Fullerene complexes with divalent metal dithiocarbamates: structures, magnetic properties, and photoconductivity

A series of complexes of fullerenes C60 and C70 with metal dithiocarbamates {MII(R2dtc)2}·Cm (m = 60 or 70) and metal dithiocarbamates coordinated to nitrogen-containing ligands (L), {MII(R2dtc)2)x·L}·C60 (x = 1 or 2), where M = Cu, Zn, Cd, Hg, Mn, or Fe, R = Me, Et, Prn, Pri, or Bun, L is 1,4-diazabicyclo[2.2.2]octane (DABCO), N,N′-dimethylpiperazine, or hexamethylenetetramine, were synthesized. The shape of dithiocarbamate molecules is sterically compatible with the spherical shape of C60, resulting in an efficient interaction between their π systems. The resulting compounds are characterized by a layered or three-dimensional packing of the fullerene molecules. In the C60 complexes, iron(II) and manganese(II) dithiocarbamates exist in the high-spin states (S = 2 and 5/2). The magnetic susceptibility of {MII(Et2dtc)2}2·Cm (M = Fe or Mn, m = 60 or 70) in the temperature range of 200–300 K is described by the Curie-Weiss law with Θ = −250 and −96 K and with maxima at 110 and 46 K, respectively, which is indicative of a strong antiferromagnetic spin coupling between MII. The Weiss constants for the [{MII(Et2dtc)2}2·DABCO]·C60·(DABCO)2 complexes (M = Fe or Mn) are 1.7 and 0.3 K, respectively. The magnetic moments of the complexes containing Fe and Mn dithiocarbamates slightly increase at temperatures below 50 and 35 K, respectively, which is evidence of the ferromagnetic spin coupling between MII in {MII(Et2dtc)2}2·DABCO. Single crystals of the complexes exhibit low dark conductivity (10−10–10−11 S cm−1). The visible light irradiation of these crystals leads to an increase in the photocurrent by two–three orders of magnitude. The photogeneration of free charge carriers in the complexes occurs both due to the photoexcitation of metal dithiocarbamate (CuII(Et2dtc)2) and through the charge transfer from metal dithiocarbamate (MII(Et2dtc)2, M = Zn or Cd) to C60.

Synthesis, Crystal Structures, Magnetic Properties and Photoconductivity of C60 and C70 Complexes with Metal Dialkyldithiocarbamates M(R2dtc)x, where M = CuII, CuI, AgI, ZnII, CdII, HgII, MnII, NiII, and PtII; R = Me, Et, and nPr

AbstractNew complexes of fullerenes C60 and C70 with metal dialkyldithiocarbamates, [M(R2dtc)x]·[C60(70)]·[Solvent], R = Et [M = CuII (C60, 1; C70, 2), CuI (C60, 3; C70, 4), AgI (C60, 5), ZnII (C60, 6), CdII (C60, 7; C70, 8), HgII (C60, 9), MnII (C70, 10)], R = Et and Me [M = CuII (C60, 11), and ZnII (C60, 12)], and R = nPr [M = CuII (C60, 13), NiII (C60, 14), and PtII (C60, 15)] were obtained. M(R2dtc)x efficiently cocrystallized with fullerene molecules as tetrahedral monomers (6, 12), dimers (1, 7, 11), and tetramers (3, 4). Fullerene molecules form closely packed hexagonal and square layers in 1, 7, and 11, hexagonal and tetragonal 3D structures in 6 and 12, and island motifs in 3 and 4. Complexes 1–15 have a neutral ground state. However, the formation of the complexes with fullerenes changes the environment of paramagnetic CuII and MnII. The EPR spectra of 1, 2, 11, and 13 are essentially modified relative to those of pristine Cu(R2dtc)2 because of a weak coordination of CuII to fullerene and a flattening of the central (NCS2)2Cu fragments. Complex 10 shows a spectrum exhibiting features from 50 to 600 mT and manifests strong antiferromagnetic coupling of spins with a Weiss temperature of –96 K and the maximum of magnetic susceptibility at 46 K. Such magnetic behavior can be explained by the formation of [Mn(Et2dtc)2]2 dimers in 10. The illumination of the crystals of 1, 2, and 7 by white light results in up to a 103 increase in photocurrent. The photoconductivity spectra have maxima at 470, 450–650, and 660 nm for 1, 2, and 7, respectively. Photogeneration of free charge carriers is realized by photoexcitation of Cu(Et2dtc)2 in 1 and 2, and by charge transfer from Cd(Et2dtc)2 to C60 molecules in 7. The decrease of photocurrent in 1 and 7 in a weak magnetic field with B0 &lt; 0.5 T was found. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2006)

Redox-Noninnocence of the S,S‘-Coordinated Ligands in Bis(benzene-1,2-dithiolato)iron Complexes

The electronic structures of complexes of iron containing two S,S'-coordinated benzene-1,2-dithiolate, (L)(2)(-), or 3,5-di-tert-butyl-1,2-benzenedithiolate, (L(Bu))(2)(-), ligands have been elucidated in depth by electronic absorption, infrared, X-band EPR, and Mossbauer spectroscopies. It is conclusively shown that, in contrast to earlier reports, high-valent iron(IV) (d(4), S = 1) is not accessible in this chemistry. Instead, the S,S'-coordinated radical monoanions (L(*))(1)(-) and/or (L(Bu)(*))(1)(-) prevail. Thus, five-coordinate [Fe(L)(2)(PMe(3))] has an electronic structure which is best described as [Fe(III)(L)(L(*))(PMe(3))] where the observed triplet ground state of the molecule is attained via intramolecular, strong antiferromagnetic spin coupling between an intermediate spin ferric ion (S(Fe) = (3)/(2)) and a ligand radical (L(*))(1)(-) (S(rad) = (1)/(2)). The following complexes containing only benzene-1,2-dithiolate(2-) ligands have been synthesized, and their electronic structures have been studied in detail: [NH(C(2)H(5))(3)](2)[Fe(II)(L)(2)] (1), [N(n-Bu)(4)](2)[Fe(III)(2)(L)(4)] (2), [N(n-Bu)(4)](2)[Fe(III)(2)(L(Bu))(4)] (3); [P(CH(3))Ph(3)][Fe(III)(L)(2)(t-Bu-py)] (4) where t-Bu-py is 4-tert-butylpyridine. Complexes containing an Fe(III)(L(*))(L)- or Fe(III)(L(Bu))(L(Bu)(*))- moiety are [N(n-Bu)(4)][Fe(III)(2)(L(Bu))(3)(L(Bu)(*))] (3(ox)()), [Fe(III)(L)(L(*))(t-Bu-py)] (4(ox)()), [Fe(III)(L(Bu))(L(Bu)(*))(PMe(3))] (7), [Fe(III)(L(Bu))(L(Bu)(*))(PMe(3))(2)] (8), and [Fe(III)(L(Bu))(L(Bu)(*))(PPr(3))] (9), where Pr represents the n-propyl substituent. Complexes 2, 3(ox)(), 4, [Fe(III)(L)(L(*))(PMe(3))(2)] (6), and 9 have been structurally characterized by X-ray crystallography.

Binuclear metal(II) (M = Co, Cu) complexes of 3,5-bi{ N,N-bis[2-(diethylamino)ethyl]aminomethyl}pyrazole

A new binucleating pyrazole ligand, 3,5-bis{ N,N-bis[2-(diethylamino)ethyl]aminomethyl}pyrazole (HL), has been synthesized. It forms cobalt( II) and copper( II) complexes of the general formula [M 2(L)(X)](BPh 4) 2· n(acetone) (M=Co, Cu; X=CH 3COO −, N 3 −; n=0–3), where two metal ions are bridged by the endogenous pyrazolate group and the exogenous X group. Electronic spectra of the cobalt(II) and copper(II) complexes suggest a trigonal-bipyramidal configuration around each metal ion. Magnetic properties have been examined over the temperature range 75–300 K. The cobalt(II) complexes [Co 2(L)(CH 3COO)](BPh 4) 2·acetone and [Co 2(L)(N 3)](BPh 4) 2·2acetone both show a slight increase of magnetic moment with lowering of temperature (from 4.03 and 3.94 μ B, respectively, at 300 K to 4.16 and 4.08 μ B, respectively, at 85 K). [Cu 2(L)(CH 3COO)](BPh 4) 2 shows a weak antiferromagnetic spin-coupling ( J = −7.02 cm −1 based on spin Hamiltonian H = −2 JŜ 1·Ŝ 2). [Cu(L)(N 3)](BPh 4) 2·acetone exhibits a much lowered magnetic moment (1.10 μ B at 300 K) owing to a strong antiferromagnetic spin coupling but its cryomagnetic property could not be simulated based on the Heisenberg model.

Synthesis and Properties of Copper(II) Perchlorate Complexes with Imino Oximes

Abstract Three types of imino oxime copper(II) complexes were obtained by the reactions of copper(II) perchlorate with imino oximes (3-[2-[(alkylamino)ethyl]imino]-2-butanone oximes or 3-[2-[(dialkylamino)ethyl]imino]-2-butanone oximes, abbreviated as Hdox-enRR′). One type contains the dinuclear complexes [Cu2(dox-enRR′)2]2+ and uncoordinated perchlorate anions. The magnetic susceptibilities measured over the temperature range 77–320 K indicate that there exists a strong antiferromagnetic spin coupling interaction through the N–O bridge in these complexes. The magnetic behavior can be explained by using the Bleaney–Bowers equation. Complexes of the second type probably contain a square-tetranuclear complex. The copper(II) ions assume a penta-coordinated configuration with perchlorate anion coordinated at the axial coordination site. It is assumed that the dinuclear and mononuclear magnetic units coexist in the complexes of the third type. The plot of the magnetic susceptibilities versus temperature is linear in the two temperature ranges (T&amp;gt;250 K, &amp;lt;100 K).

Synthesis and Properties of Copper(II) Halide Complexes with Imino Oximes

Abstract Two types of imino oxime copper(II) complexes were obtained by the reactions of copper(I) halides CuX (X=Br, I) with imino oximes (3-[2-[(alkylamino)ethyl]imino]-2-butanone oximes or 3-[2-[(dialkylamino)ethyl]imino]-2-butanone oximes, abbreviated as Hdox-enRR′). One type contains the binuclear complexes [Cu2(dox-enRR′)2]2+ and uncoordinated halide anions. The magnetic susceptibilities measured over the temperature range 77–320 K show a strong antiferromagnetic spin coupling interaction through the N–O bridge in these complexes. The magnetic behavior can be explained by using the Bleaney–Bowers equation. It is assumed that the complexes of the other type consist of copper(I) and copper(II) in 2:1 ratio without spin-coupling interaction between the copper ions. The plot of the reciprocal magnetic susceptibilities versus temperatures is linear.

Synthesis and Properties of Copper(II) Thiocyanato Complexes with Imino Oximes

Abstract Reaction of copper(I) thiocyanate with imino oximes 3-[[2-(alkylamino)ethyl]imino]-2-butanone oximes or 3-[[2-(dialkylamino)ethyl]imino]-2-butanone oximes, (abbreviated as Hdox-enRR′), gave a series of copper(II) complexes which consist of binuclear complexes [Cu2(dox-enRR′)2(NCS)2] with a thiocyanate anion coordinated to the copper(II) ion. The magnetic susceptibilities over the temperature range 77–320 K show a strong antiferromagnetic spin coupling through the N–O bridge for these complexes. The magnetic behavior can be explained by using the Bleaney–Bowers equation.

ChemInform Abstract: CRYSTAL AND MOLECULAR STRUCTURES AND MAGNETIC PROPERTIES OF FOUR NEW EXCHANGE‐COUPLED COPPER(II) COMPLEXES DERIVED FROM DIFFERENT 3‐N,N‐DIALKYLAMINO‐1‐PROPANOLS AND PSEUDOHALOGENS

The crystal and molecular structures of (3-N,N-dimethylamino-1-propanolato) isocyanatocopper(II)(1), (3-N,N-dimethylamino-1-propanolato) isothiocyanatocopper(II)(2), (3-N,N-diethylamino-1-propanolato) isothiocyanatocopper(II)(3), and (3-N,N-di-n-butylamino-1-propanolato)isothiocyanatocopper(II)(4) have been determined using three-dimensional X-ray diffractometer data. Final R values were 0.0237 for (1), 0.0250 for (2), 0.0297 for (3), and 0.0464 for (4). Compounds (1) and (2) crystallize in monoclinic lattices (space group P21/c), (3) and (4) in triclinic ones (space group P). The structure of (1) consists of an infinite two-dimensional network of alkoxo-bridged dimers connected by cyanato-groups in the plane (100); the three remaining structures consist of infinite chains of alkoxo-bridged dimers connected by the thiocyanato-groups. Within the dimeric units the copper atoms have distorted square-planar co-ordination. The connection between the dimers leads to a fifth co-ordination with longer copper–ligand bonds. The magnetic susceptibilities measured from 11.1 K show for all four compounds very strong antiferromagnetic spin coupling (|2J| > 850 cm–1). A correlation between the exchange constants and the Cu–O–Cu′ bridging angles within the dimers for all known (3-N,N-dialkylamino-1-propanolato)-halogenocopper(II) and -pseudohalogenocopper(II) complexes is given and shows that these complexes are systematically more strongly coupled than the related complexes derived from analogous aminoethanols.

Crystal and molecular structures and magnetic properties of four new exchange-coupled copper(II) complexes derived from different 3-N,N-dialkylamino-1-propanols and pseudohalogens

The crystal and molecular structures of (3-N,N-dimethylamino-1-propanolato) isocyanatocopper(II)(1), (3-N,N-dimethylamino-1-propanolato) isothiocyanatocopper(II)(2), (3-N,N-diethylamino-1-propanolato) isothiocyanatocopper(II)(3), and (3-N,N-di-n-butylamino-1-propanolato)isothiocyanatocopper(II)(4) have been determined using three-dimensional X-ray diffractometer data. Final R values were 0.0237 for (1), 0.0250 for (2), 0.0297 for (3), and 0.0464 for (4). Compounds (1) and (2) crystallize in monoclinic lattices (space group P21/c), (3) and (4) in triclinic ones (space group P). The structure of (1) consists of an infinite two-dimensional network of alkoxo-bridged dimers connected by cyanato-groups in the plane (100); the three remaining structures consist of infinite chains of alkoxo-bridged dimers connected by the thiocyanato-groups. Within the dimeric units the copper atoms have distorted square-planar co-ordination. The connection between the dimers leads to a fifth co-ordination with longer copper–ligand bonds. The magnetic susceptibilities measured from 11.1 K show for all four compounds very strong antiferromagnetic spin coupling (|2J| > 850 cm–1). A correlation between the exchange constants and the Cu–O–Cu′ bridging angles within the dimers for all known (3-N,N-dialkylamino-1-propanolato)-halogenocopper(II) and -pseudohalogenocopper(II) complexes is given and shows that these complexes are systematically more strongly coupled than the related complexes derived from analogous aminoethanols.

Crystal and molecular structures and magnetic properties of bromo(3-dimethylaminopropan-1-olato)copper(II), chloro(3-dimethylaminopropan-1-olato) copper(II), and (3-diethylaminopropan-1-olato)isocyanatocopper(II)

The crystal and molecular structures of the title compounds have been determined using three-dimensional X-ray diffractometer data and refined to a final R value of 0.0263 for bromo(3-dimethylaminopropan-1-olato)copper(II)(1), 0.0349 for chloro(3-dimethylaminopropan-1-olato)copper(II)(2), and 0.0268 for (3-diethylaminopropan-1-olato)isocyanatocopper(II)(3). The compounds crystallize in the monoclinic space group P21/c. The unit-cell dimensions are a= 6.273(3), b= 10.282(5), c= 12.403(5)A, β= 99.62(2)°, Z= 4 for (1); a= 7.484(3), b= 6.145(3), c= 17.152(6)A, β= 101.55(2)°, Z= 4 for (2); and a= 7.363(3), b= 12.422(5), c= 11.117(5)A, β= 96.37(2)°, Z= 4 for (3). The structures of (1) and (2) consist of infinite chains of alkoxo-bridged copper(II) dimers connected by halogen bridges with long halogen–copper bonds [3.127(1)A for (1) and 2.905(1)A for (2)]. Neglecting these additional fifth co-ordination sites the co-ordination of the copper ions is distorted square planar. The structure of (3) consists of discrete dimeric molecules. The copper–copper distances are 3.063(1) for (1), 3.060(1) for (2), and 3.044(1)A for (3). The magnetic susceptibilities measured from 11.1 K show very strong antiferromagnetic spin coupling for all three compounds. The magnetic behaviour can be explained using the Bleaney–Bowers equation. By fitting the experimental data to the Bleaney–Bowers equation good agreement can be obtained with the parameters g= 2.18(2), 2J12=–1 065(20) cm–1, x= 0.004(1), Nα= 63(5)× 10–6 c.g.s.u. for (1), g= 2.21 (2), 2J12=–1 020(20) cm–1, x= 0.003(1), Nα= 54(5)× 10–6 c.g.s.u. for (2) and g= 2.26(2), 2J12=–1 056(20) cm–1, x= 0.013(3), Nα= 108(5)× 10–6 c.g.s.u. for (3). The evident differences between these results and those expected from magnetostructural correlations for related compounds are discussed. A magnetostructural correlation is presented which shows the influence of the co-ordination geometry at the copper atom on the exchange interaction in spin-coupled alkoxo-bridged copper(II) complexes.