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Four isostructural LnZn2 trinuclear complexes, [Ln(NO3){Zn(L)(SCN)}2] (H2L is a Schiff base ligand derived from o-vanillin and ethylenediamine), were synthesized, which include light lanthanide ions as spin carriers (Ln = Ce 1, Pr 2, Nd 3, and Sm 4). These complexes involve a linear Zn(ii)-Ln(iii)-Zn(ii) array, which leads to an axially stressed ligand field and can also cause single-moleluce magnet (SMM) behavior in oblate-type electronic distributions of ground sublevels found in Ce(iii), Pr(iii), and Nd(iii). Slow magnetic relaxation behavior was observed in 1 and 3 under an applied bias dc field of 1000 Oe, whereas such a slow relaxation was not observed in 2 and 4. The appearance of field-induced SMM behavior in 1 and 3 was correlated with the even-numbered Jz sublevels of Ce(iii) and Nd(iii) ions known as the Kramers system.

A cobalt molecule that functions as a single-molecule magnet, [Co[sub 4](hmP)[sub 4](MeOH)[sub 4]Cl[sub 4]], where hmp[sup -] is the anion of hydroxymethylpyridine, is reported. The core of the molecule consists of four Co(II) cations and four hmp[sup -] oxygen atom ions at the corners of a cube. Variable-field and variable-temperature magnetization data have been analyzed to establish that the molecule has a S = 6 ground state with considerable negative magnetoanisotropy. Single-ion zero-field interactions (DS²[sub z]) at each cobalt ion are the origin of the negative magnetoanisotropy. A single crystal of the compound was studied by means of a micro-superconducting quantum interference device magnetometer in the range of 0.040-1.0 K. Hysteresis was found in the magnetization versus magnetic field response of this single crystal. [ABSTRACT FROM AUTHOR]

The article discusses the roles played by heat-capacity calorimetry in the fields of molecule-based magnetism by focusing on phase transitions occurring not only under ambient pressure but also under applied pressure and magnetic field. The molecule-based magnets demonstrate low-dimensionality concerning the magnetic lattices formed by magnetic interactions, because of structural anisotropy inherent in the constituent molecule moieties. Traditional adiabatic calorimetry is still considered as the most precise and accurate heat-capacity calorimetry.

The magnetic behavior of the nickel cubane complex [Ni 4 (Ome) 4 -(sal) 4 (MeOH) 4 ](Hsal=salicylaldehyde) was studied by using a Hartshorn bridge equipped with a 3 He/ 4 He dilution refrigerator. This complex has long been known to have a well-isolated high-spin ground state with S =4 and it was suggested to have an easy-axis type anisotropy. AC magnetic susceptibility data clearly show a slow magnetization reversal below 0.3 K, characteristic of single-molecule magnets. The Arrhenius plot of the relaxation rate provides the activation energy of about 5 K. [ABSTRACT FROM AUTHOR]

A manganese single-chain magnet, [Mn6O2(4-MeOsalox)6(N3)2(MeOH)4]n(4-MeO-H2salox = 2-hydroxy-4-methoxybenzaldehyde oxime), is synthesized viathe assembly of Mn6single-molecule magnets, which exhibits a large magnetic coercivity. [ABSTRACT FROM AUTHOR]

This article reports on an unusual single-chain magnet (SCM) formed by a twisted arrangement of ions with easy-plane magnetic anisotropy. The attention of nanoscientists is currently directed toward the behaviors of nanomagnets, such as single-molecule magnets and SCMs, since they show unique physical properties, such as quantum tunneling of magnetization and quantum phase interference, that are not observed in bulk magnets. An alternating Fe²/Fe³ mixed valence single-chain magnet was prepared using the complexed ligand. This twisting easy plane system is unique in that it exhibits easy-axis anisotropy over the whole chain, giving rise to stow magnetization reversal despite single ion anisotropy of the constituent Fe² ions with easy-plane.

Abstract: The reaction of salicylaldoxime (H2salox) with Mn(ClO4)2 ·6H2O, NaN(CN)2 and NEt3 in MeOH affords a MnIII 6 hexanuclear complex of [Mn6O2(salox)6(MeOH)6(NCNCONH2)2] (1), while reaction of H2salox with MnCl2 ·4H2O and NEt4OH in EtOH affords a MnIII 6 hexanuclear complex of [Mn6O2(salox)6(EtOH)4(H2O)2Cl2] (2). Both complexes 1 and 2 contain a [MnIII 6(μ3-O)2]14+ core, which is a known structural type in the family of Mn6 complexes. Variable temperature magnetic susceptibilities and magnetization measurement of complexes 1 and 2 have been carried out. Exchange interactions of metal centers for complexes 1 and 2 are fitted by a full diagonalization matrix method. The fitting results indicate that both complexes 1 and 2 have the ground-state spin value of S =4, and the ground state of complex 1 has the much closer energy to low-lying spin states than that of complex 2. Magnetization measurements at 2.0–4.0K and 10–70kG confirm that the ground state is S =4, with significant magnetoanisotropy as gauged by the D value of −0.82cm−1 and −1.18cm−1, for 1 and 2, respectively. The frequency dependence of the out-of-phase component in alternating current magnetic susceptibilities for both complexes 1 and 2 indicates the slow magnetic relaxation of superparamagnetic behaviour with a U eff of 27.0(1)K and τ 0 =3.8(2)×10−9 s for complex 1, and U eff of 25.1(6)K and τ 0 =4.6(1)×10−8 s for complex 2. [Copyright &y& Elsevier]

Examines the heat capacities of the single-molecule magnet [Mn[sub 12]O[sub 12](O[sub 2]CEt)[sub 16](H[sub 2]O[sub 3]]. Measurement on the accurate heat capacity of the single-molecule magnet through adiabatic calorimetry; Attribution factor to the tiny thermal anomaly between 1 and 2 K; Discussion on the heat dependence of the molecule.

Detailed synthetid, structural, and magnetic characterizations for a family of six [Mn[sub3]Zn[sub2]][sup13+] complexes are presented. These complexes have planar [Mn[sub3][supIII]-(μ[sub3]-oxo)][sup7+] core magnetic units and have formulas represented by [cation][sub3][Mn[sub3]Zn[sub2](R- salox)[sub3]O(N[sub3])[sub6]X[sub2]], where [cation][sup+] = [NEt[sub4]][sub3][sup+] or [AsPh[sub4]][sub3][sup+] R = H or Me; and X = Cl, Br-, L, or N3-. Least-squares fits to the magnetic susceptibility data for these complexes indicate large negative values of the axial zero field splitting (ZFS) parameter D (≈ -1.1K) and spin ground states ranging from a highly spin-mixed S ≈ 1 to a reasonably isolated S = 6 (ΔE[subs=5]=69.2 K). The strength and magnitude of the intramolecular exchange interactions have been observed to change with the crystal packing as a result of systematic vanations in the co-crystallizing cation, terminal ion, and oximate ligand. Altemating current susceptibility data were collected from 1.8-7 K at 10-997 Hz, revealing strong frequency-dependent peaks in the out-of-phase susceptibility (χ''M) for ferromagnetic S = 6 complexes 1, 2, and 6. Fitting of these data to the Arthenius equation gave U[subeff]=44.0 K and ...[sub0] = 3.8 x 10[sup-8] s for [NEt[sub4]][sub3][Mn[sub3]Zn[sub2](salox)[sub3]O(N[sub3])[sub6]Cl[sub2]] (1), and U[subeff] = 45.6 K and ...[sub0] = 2.1 x 10[sup-7] s for [NEt[sub4]][sub3][Mn[sub3]Zn[sub2](Me-salox)[sub3]O(N[sub3])[sub6]Cl[sub2]] (6). The enhanced relaxation behavior in complex 6 is associated with stronger ferromagnetic exchange interactions and a more isolated S = 6 ground state thafl in 1 and 2. Comprehensive high-frequency electron paramagnetic resonance (HFEPR) expenments were conducted on single crystals of complexes 1, 2, and 6, revealing sharp absorption peaks and allowing for the precise determination of ZFS parameters. Similar expenments on [AsPh[sub4]][sub3][Mn[sub3]Zn[sub2](salox)[sub3]O(N[sub3])[sub6]Cl[sub2]] (4) resulted in the observation of a broad absorption peak, consistent with the highly spin-mixed ground state. Single crystal magnetization hysteresis measurements on complexes 1 and 2 indicate SMM behavior via temperature- and sweep-rate dependent hysteresis loops and the observance of very sharp quantum tunneling resonances. Additionally, the Hamiltonian parameters denved from the magnetic data, HFEPR, and hysteresis measurements are in good agreement and highlight the relationships between superexchange, spin-orbit interactions, and the varied relaxation behavior in these complexes. [ABSTRACT FROM AUTHOR]

Five N-aryl-N-pyridylaminoxyls, which have no substituent (PhNOpy), one substituent (MeOPhNOpy and tert-BuPhNOpy) at the 4-position, and three substituents (TPPNOpy and TBPNOpy) at the 2, 4, and 6-positions of the phenyl ring, were prepared as new ligands for cobalt-aminoxyl heterospin systems. The 1:4 complexes, [Co(NCS)2(PhNOpy)4] (1), [Co(NCS)2(MeOPhNOpy)4] (2), [Co(NCS)2(tertBuPhNOpy)4] (3), [Co(NCS)2(TPPNOpy)4] (4), [Co(NCS)2(TBPNOpy)4] (5a), and [Co(NCO)2(TBPNOpy)4] (5b), were. obtained as single crystals. The molecular geometry revealed by X-ray crystallography for all complexes except 4 is a compressed octahedron. In the crystal structure of 1, 2, and 3, the organic spin centers have various short contacts within 4 A with the neighboring molecules to form 3D and 2D spin networks. On the other hand, complexes 5a and 5b have no significant short intermolecular contacts, indicating that they are magnetically isolated. 1 and 2 behaved as a 3D antiferromagnet with a Neel temperature, TN, of 22 K and as a weak 3D antiferromagnet with a TN of 2.9 K and a spin-flop field at 1.9 K, Hsp(1.9), of 0.7 kOe, respectively. 3 was a canted 2D antiferromagnet (a weak ferromagnet) with TN = 4.8 K and showed a hysteresis loop with a coercive force, Hc, of 1.3 kOe at 1.9 K. On the other hand, the trisubstituted complexes 4, 5a, and 5b functioned as single-molecule magnets (SMMs). 5b had an effective activation barrier, Ueff, value of 28 K in a microcrystalline state and 48 K in a frozen solution. [ABSTRACT FROM AUTHOR]

Two new heterometallic cubane molecules have been synthesized. High-frequency electron paramagnetic resonance and magnetization measurements indicate that [Mn3Ni(hmp)3O(N3)3(C7H5O2)3] (1) displays a well-isolated S = 5 ground state (ΔE> 120 K), with g = 2.0, D = -0.23 cm-1, and ferromagnetic Mn-Mn exchange interactions competing with antiferromagnetic Ni-Mn interactions. [Mn3Zn(hmp)3O(N3)3(C3H5O2)3] (2) possesses a S = 6 ground state (ΔE> 105 K), with g = 2.0, 0 = -0.14 cm-1, and ferromagnetic Mn-Mn exchange interactions. Magnetization vs magnetic field data for oriented single crystals of 1 and 2 indicate that both complexes are single-molecule magnets. [ABSTRACT FROM AUTHOR]

A one-dimensional chain of interconnected single-molecule magnets (SMMs) is obtained that consists of [Mn4(hmp)6]4+ units bridged by chloride ions. Slow magnetization relaxation is evident in the AC susceptibility data and in magnetization hysteresis measurements for [Mn4(hmp)6Cl2]n(ClO4)2n. The magnetization hysteresis loops for this complex are similar to those for an SMM and show significant coercive field and steps at regular magnetic intervals. Spin-canted antiferromagnetic coupling due to misalignment of easy axes of neighboring Mn4 units is also observed for this complex. [ABSTRACT FROM AUTHOR]