摘要:

Hydrogen bonded coordination polymers, {[CU(CA)(H2O)2(H2O)}n, [Cu(CA)(MeOH)2n(H2CA; chloranilic acid), and related polycrystalline analogs have been structurally and magnetically characterized. 1-Dimensional (1-D) weak antiferromagnetic exchange interaction (J= -2.01 cm−1) was observed in {[Cu(CA)(H2O)2(H2O)}n, which has a 3-dimensional hydrogen bond network in the crystal. This polycrystalline form liberates the water molecules to be [Cu(CA)n, which is known as the Heisenberg antiferromagnet. Powder X-ray diffraction and thermal data show that the framework constructed by 1-D chains are so stable that water molecules readily come out without breaking the 1-D chains. Two types of coordination polymers ([Cu(CA)(MeOH)2nand [Cu(CA)(MeOH)n) containing axially coordinated MeOH have been prepared. [Cu(CA)(MeOH)nhas strong and anomalous antiferromagnetic exchange interactions in the crystal, indicating a new phase of Cu/CA systems, such as a mixed valence state, and if so the coordinated MeOH plays an important role to control physical properties of the polymers.

ISSN:1058-725X    

DOI:10.1080/10587259508031879

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Weakly associated five coordinate monomers based on high-spin trivalent iron α-di-imine complexes are found to exhibit surprisingly strong magnetic exchange interactions that lead to easily discerned 1-and 3-dimensional antiferromagnetic exchange and ordering effects respectively.

ISSN:1058-725X    

DOI:10.1080/10587259508031880

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A general approach is developed in order to calculate the energy levels and magnetic properties of high nuclearity mixed valence clusters. The approach considers all the relevant electronic processes, namely (i) interelectronic Coulomb repulsion between the moving electrons, which depend on the different distributions of the electronic pairs over the available metal sites; (ii) single and double electron transfer processes, which promotes the electron delocalization; (iii) magnetic exchange interactions. This approach is applied here to tetranuclear iron (II)-iron (III) clusters for symmetries comprised between tetrahedral and square planar.

ISSN:1058-725X    

DOI:10.1080/10587259508031881

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Iron (3+) and cobalt (2+) polyorganosiloxanes were synthesized and characterized magnetically. The cobalt containing polymers were found to have a ferromagnetic ground state with a mean value of J of about 10K. The iron containing polymers demonstrated both ferromagnetic coupling with a mean J value ranging from 10 to 50K (depending on Fe concentration) and antiferromagnetic interaction with an exchange constant having an absolute magnitude of about 10 times less. Several models were developed to fit the experimental data. For both systems the best model found was the following: ion-ion coupling (5/2+5/2 for Fe and 3/2+3/2 for Co) arising from interactions within the polymeric chain, complicated by inter-chain interactions which are positive and negative for Co and Fe, respectively. A molecular field approximation was used to calculate the contribution of this interaction.

ISSN:1058-725X    

DOI:10.1080/10587259508031882

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Polymers of acrylonitrile, Mtilon (Mt) - cyanoethylated cellulose hydrate [(C6H7O2)3-x(OCH2CH2CN)xand Nitron (Nt) - commercial acrylic fiber containing 10–60% carboxylic groups have been specially prepared and modified by various metals (Fe, Co, Ni). Subsequent special thermal treatment yielded polymers containing metal nanosize clusters (40–200 Å) dispersed in the polymer matrix whose ferromagnetic properties has been thoroughly studied. The chief reasons hindering the creation of high-Tcmolecular/polymer-based ferromagnets are determined and analyzed. The concept of fractal ferromagnetic exchange interaction between magnetic moments of neighboring nanosize metal clusters via polyconjugated system is proposed. A new effect of an increase in the specific saturation magnetizationμsof metal atoms in clusters is reported. The effect is explained by the spin polarization of the polyconjugated matrix coating the metal clusters, somewhat similar to the chemical polarization of spins of electrons in a fractal geometry of clusters.

ISSN:1058-725X    

DOI:10.1080/10587259508031883

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:1058-725X    

DOI:10.1080/10587259508031858

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor