摘要:

2-Dicyanomethylene-1,3-dithiole-4,5-dithiolate (DCDD) has been prepared and used for the synthesis of transition metal complexes (Bu4N)2[M(DCDD)2], M = Ni, Cu, Zn. The redox properties of the nickel complex are similar to that of (Bu4N)2[Ni(dmit)2] (dmit: 1,3-dithiole-2-thione-4,5 dithiolate). Oxidation of (Bu4N)2[Ni(DCDD)2] yields the monoanionic complex Bu4N[Ni(DCDD)2] the electron spectrum of which is characterized by a strong NIR absorption at 1135 nm. The crystal structure of Bu4N[Ni(DCDD)2] shows the anion to be almost planar. Face-to-face stacking of the anions with alternating Ni-Ni distances results in a columnar structure of dimeric anions. The spins of the anions within a dimer are anti-ferromagnetically coupled. The complex Fc*[Ni(DCDD)2] (Fc*: decamethyl-ferrocene) has been prepared by a metathesis reaction using Fc*BF4.

ISSN:1058-725X    

DOI:10.1080/10587259508031835

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The five integrated-stack charge-transfer salts [M(C5Me5)2][TCNQ] (M═Mn,Cr) and [M(C5Me5)2][TCNE] (M═Fe, Mn, Cr) are bulk ferromagnets, whereas [Fe(C5Me5)2][TCNQ] was reported to exist as two different phases, a metamagnet and a paramagnet. We now report that with careful control of the crystallization conditions, it is possible to isolate a new structural phase of [Fe(C5Me5)2][TCNQ] which is a bulk 3-D ferromagnet with Tc= 3.1 K. Thus [Fe(C5Me5)2][TCNQ] is the first example of a single compound giving rise to three distinctly different magnetic phenomena, a finding that will permit an assessment of the subtle structural features that control magnetic ordering in this class of materials.

ISSN:1058-725X    

DOI:10.1080/10587259508031836

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Mono- and dimetallic building blocks are being studied in charge-transfer reactions with organic π-acceptors such as TCNE to form zero-, one-, and two-dimensional hybrid donor/acceptor compounds. In particular, tetracarboxylate-bridged dinuclear and solvated 3d mononuclear complexes with [sgrave]-bonded TCNE ligands are being investigated with regards to their variable temperature magnetic behavior. Results of experiments with dimolybdenum, diruthenium and vanadium complexes are discussed.

ISSN:1058-725X    

DOI:10.1080/10587259508031837

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The synthesis, crystal structure and magnetic properties of the title compound are presented: Fe[C5(CH3)5]2[Ni(III)(S4C3O)2](CH3CN), Mr = 786.65, crystallizes in the C2/m monoclinic space group with cell parameters a=16.374(4) Å, b=10.84(2)Å, c=19.530(5)Å, β=98.02(2)°, V = 3431 Å3, Z = 4, dcalc= 1.523 g.cm−3, Full-matrix least-squares refinements gave R(F) = 0.060, Rw(F) = 0.077 based on 1068 reflections with >3[sgrave](I). The magnetic behavior is typical of dominant ferromagnetic interactions to which very weak antiferromagnetic interactions are superimposed.

ISSN:1058-725X    

DOI:10.1080/10587259508031838

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We report the synthesis and physical properties of compounds of BEDT-TTF with transition metal tris-oxalate anions. The crystal structure of one such compound, (BEDT- T TF)4KFe(C2O4)3C6H5CN (1) has been determined. The structure consists of alternating layers of BEDT-TTF and a hexagonal network of K+and Fe(C2O4)33-. This material is a semiconductor with an activation energy of 0.14eV. Magnetic data obey the Curie-Weiss law with C = 4.44 (S=5/2) and O= −0.25K.

ISSN:1058-725X    

DOI:10.1080/10587259508031839

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We report measurements of the magnetic properties of the molecular magnet NH4Ni(mnt)2.H2O. The magnetic exchange in this salt is ferromagnetic below 100K, with a Weiss constant of 7 K. Long range magnetic ordering is observed below 5 K. Single crystals of this salt have been studied down to 2 K in a SQUID magnetometer. The salt is found to have hard and easy magnetisation directions. Magnetisation of 1800 emuG/mol at 2 kOe was measured at 2 K for magnetic fields applied perpendicular to the molecular stacking axis.

ISSN:1058-725X    

DOI:10.1080/10587259508031840

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Orthogonal arrangement of iminonitroxides in [Cu1(immepy)2](PF6) (1) and [Ag1(impy)2](PF6) (2) results in propagation on intramolecular ferromagnetic interaction between coordinating iminonitroxides through these diamagnetic ion. In1, iminonitroxides coordinate to the Culion in a tetrahedral fashion, the dihedral angle between coordinating iminonitroxides being 88.7°. Magnetic susceptibility and epr measurements for1show the typical ferromagneic behavior with large zero field splitting (2J= 91(1) cm−1(H= −2JS1.S2);D= 3.62 cm−1). In 2, the four coordination sites of Ag1ion were completed with two iminonitroxides and the dihedral angle between the iminonitroxides is 79.2°. Temperature dependence of teh epr spectra for frozen ethanol solution of 2 shows that the intramolecular mangetic interaction between radicals is ferromagnetic (0= 4K).

ISSN:1058-725X    

DOI:10.1080/10587259508031841

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The ferromagnetism of β-phasep-nitrophenyl nitronyl nitroxide has been established by various measurements at an ambient pressure. To get further insight into the magnetic interactions, the pressure effect on the magnetic and thermal properties has been examined in the pressure range of 0–7.7 kbar. Important feature of the results is twofold. One is a reduction of the Curie temperature with applied pressure. This suggests that the exchange interactions are mainly responsible for determination of the Curie temperature. Dipolar couplings are estimated to be too small to explain the observed Curie temperature. The other is the lowering of the lattice dimensionality. The heat capacity curve under the pressure of 7.2 kbar coincides with the theory for a two-dimensional Heisenberg ferromagnet above the Curie temperature. This suggests that the interactions between the neighboringac-plane are more affected by compression of the crystal.

ISSN:1058-725X    

DOI:10.1080/10587259508031842

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Organic di-and trinitroxide radicals with triplet and quartet ground states, respectively, were allowed to react with manganese(II) bis(hexafluoroacetylacetonate)to give polymer complexes having well-defined dimensionality. While 1:1 1-D complex from them-phe-nylenebis(nitroxide) was found to be a metamagnet (Tc= 5.5 K), 2:3 2-D complexes from the trinitroxides became ferr/ferromagnets withTcin the range 3.4–46 K, demonstrating the merit of these hetero-spin systems as a design strategy for molecule-based magnets.

ISSN:1058-725X    

DOI:10.1080/10587259508031843

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The complex Mn(NITImH)3(CIO4)2[NITImH═2-(2-imidazolyl)-4,4,5,5,-tetramethyl-4,5-dihydro- 1H-imidazolyl-1-oxy)] has been synthesized. It crystallizes in the monoclinic space group P2t/n, with a=15.832(3)Å b = 10.346(3)Å, c = 26.029(4)Å β = 106.78(1)° and Z = 4. The crystal structure consists of [Mn(NITImH)3]2+cations and non-coordinated perchlorate anions. Each NITImH nitronyl nitroxide radical is bis-chelated to the manganese(II) ion through an oxygen atom of one of its NO groups and a nitrogen atom of the imidazolyl substituent. The coordination geometry around the manganese(II) ion is slightly distorted from octahedral. The perchlorate anions weakly hydrogen bond the [Mn(NITImH)3]2+cations in a tridimensional network. Cryomagnetic investigations in the range 2–300K revealed a strong antiferromagnetic behavior. The χT product is 2.9 lcm3.K.mol−1at 300K, reaches a plateau (1.00 cm3.K.mol−1) between 65 and 15K, then decreases abruptly. The experimental magnetic data were fit assuming identical nitroxide-manganese(II) coupling J = −53cm−1based on the isotropic model H= −2ΣJijSiSjassociated with an intermolecular antiferromagnetic interaction Z'J' = −1.4cm−1based on the molecular field approximation and g = 2.06.

ISSN:1058-725X    

DOI:10.1080/10587259508031844

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor