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AMBIENTUM BIOETHICA BIOLOGIA CHEMIA DIGITALIA DRAMATICA EDUCATIO ARTIS GYMNAST. ENGINEERING EPHEMERIDES EUROPAEA GEOGRAPHIA GEOLOGIA HISTORIA HISTORIA ARTIUM INFORMATICA IURISPRUDENTIA MATHEMATICA MUSICA NEGOTIA OECONOMICA PHILOLOGIA PHILOSOPHIA PHYSICA POLITICA PSYCHOLOGIA-PAEDAGOGIA SOCIOLOGIA THEOLOGIA CATHOLICA THEOLOGIA CATHOLICA LATIN THEOLOGIA GR.-CATH. VARAD THEOLOGIA ORTHODOXA THEOLOGIA REF. TRANSYLVAN
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The STUDIA UNIVERSITATIS BABEŞ-BOLYAI issue article summary The summary of the selected article appears at the bottom of the page. In order to get back to the contents of the issue this article belongs to you have to access the link from the title. In order to see all the articles of the archive which have as author/co-author one of the authors mentioned below, you have to access the link from the author's name. |
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STUDIA PHYSICA - Issue no. SPECIAL ISSUE / 2001 | |||||||
Article: |
X AND W ESR STUDIES OF TRANSITION METAL CLUSTERS ENCAPSULATED IN SANDWICH-TYPE POLYOXOMETALATES. Authors: O. COZAR, L. DAVID, VASILE CHIŞ. |
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Abstract: The series of sodium/potassium salts of the sandwich-type heteropolyanions [Mn+3(H2O)x(BiW9O33)2](183n) (Mn+ = (VO)II, x = 0 and Mn+ = CrIII, MnII, FeIII, CoII, NiII, CuII, x = 3) was investigated by X and W bands ESR spectroscopy. In the complex with vanadium(IV) the unpaired electrons are trapped on the parent ions (gII = 1.899, g = 1.974, AII = 184 G, A = 69 G) and the VIV ions are prevalently dipolar coupled. In the case of the other trinuclear clusters, the metallic coupling is based on the superexchange mechanism realized through the heteropolyoxometalate frame. The isotropic exchange constants were estimated for the CrIII (J = 4.116 cm1) and MnII (J = 2.074 cm1) clusters from the temperature dependance of the linewidths of the HF-EPR signals. The g tensor is isotropic for the complexes with CrIII, MnII and FeIII (g 2.0), axial for the CuII cluster (gII = 2.080, g = 2.237) and rhombic for the NiII complex (gx = 2.201, gy = 2.211, gz = 2.292). The zero field splitting tensor is rhombic for the clusters of MnII (D = 0.381 cm1, E = 0.054 cm1 for the spin state S = 7/2) and NiII (D = 1.66 cm1, E = 0.18 cm1 for the spin state S = 1). Two species with different degrees of the rhombical distortion have been identified in case of the FeIII (D1 = 1.5 cm1, E1 = 0.12 cm1 and D2 = 1.5 cm1, E2 = 0.5 cm1) and CoII (gx1 = 5.021, gy1 = 3.561, gz1 = 2.401 and gx2 = 5.776, gy2 = 3.813, gz2 = 2.850) samples. | |||||||
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