Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Unusual ferromagnetic couplings in single end-to-end azide-bridged cobalt(II) and nickel(II) chain systems
Autore:
Hong, CS; Koo, JE; Son, SK; Lee, YS; Kim, YS; Do, Y;
Indirizzi:
Korea Adv Inst Sci & Technol, Dept Chem, Sch Mol Sci BK21, Taejon 305701, South Korea Korea Adv Inst Sci & Technol Taejon South Korea 305701 5701, South Korea Korea Adv Inst Sci & Technol, Ctr Mol Design & Synth, Taejon 305701, SouthKorea Korea Adv Inst Sci & Technol Taejon South Korea 305701 05701, SouthKorea Korea Basic Sci Inst, Taejon 305333, South Korea Korea Basic Sci Inst Taejon South Korea 305333 aejon 305333, South Korea
Titolo Testata:
CHEMISTRY-A EUROPEAN JOURNAL
fascicolo: 19, volume: 7, anno: 2001,
pagine: 4243 - 4252
SICI:
0947-6539(20011001)7:19<4243:UFCISE>2.0.ZU;2-X
Fonte:
ISI
Lingua:
ENG
Soggetto:
ALTERNATING S=1 CHAIN; MAGNETIC-PROPERTIES; CRYSTAL-STRUCTURE; MAGNETOSTRUCTURAL CORRELATIONS; MU-AZIDO; WEAK FERROMAGNETISM; DINUCLEAR COMPLEXES; PHASE-TRANSITIONS; MANGANESE(II); COMPOUND;
Keywords:
azide; cobalt; magnetic properties; nickel; spin canting;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
51
Recensione:
Indirizzi per estratti:
Indirizzo: Lee, YS Korea Adv Inst Sci & Technol, Dept Chem, Sch Mol Sci BK21, Taejon 305701, South Korea Korea Adv Inst Sci & Technol Taejon South Korea 305701 uth Korea
Citazione:
C.S. Hong et al., "Unusual ferromagnetic couplings in single end-to-end azide-bridged cobalt(II) and nickel(II) chain systems", CHEM-EUR J, 7(19), 2001, pp. 4243-4252

Abstract

Two new one-dimensional single azide-bridged metal(II) compounds [{M(5-methylpyrazole)(4)(N-3)}(n)]- (ClO4)(n)(H2O)(n) [M=Co (1a), Ni (2a)] were prepared by treating an M-11 ion with stoichiometric amount of sodium azide in the presence of four equivalents of the 3(5)-methylpyrazole ligand. The isostructural compounds la and 2a crystallize in the monoclinic space group P2(1)/n. The azide bridging ligands have a unique end-to-end coordination mode that brings two neighboring metal centers into a cis-position with respect to the azide unit to form single end-to-end azide-bridged cobalt(ii) and nickel(ii) chains. The two neighboring metal atoms at inversion centers adopt octahedral environments with four equatorial 3(5)-methylpyrazole ligandsand two axial azide bridges. Two adjacent equatorial least-squares planes form dihedral angles of 60.5 degrees and 60.6 degrees for Cc and Ni. respectively. In addition, the metalazide-metal units form large M-N-3-M torsion angles, which are magnetically important geometrical parameters, of 71.6 degrees for M = Co and 75.7 degrees for M = Ni. It should also be noted that the M-N-N angles associated with end-to-end azide group, another magnetically important structural parameter, fall into the experimentally observed range of 120- 140 degrees as 128.3(3) and 147.8(3)degrees for cobalt species and 128.4(2) and 146.1(3)degrees for nickel species, these values deviate from the theoretical value of around 164 degrees at which the incidental orthogonality is achieved under the torsion angle of 0 degrees. The compounds la and 2a have unique magnetic properties of ferromagnetism, zero-field splitting, and spin canting. The MO calculations indicate that the quasiorthogonality between the magnetic orbitals of metal ions and the p atomic orbitals of the bridging azide is possible in the observed structures and leads to the ferromagnetism. The spin canting related to the perturbation of ferromagnetism arises from the magnetic anisotropy and antisymmetric interactions judged by the structural parameters of the zero-field splitting and the tilted MN4 planes in a chain. The enhancement of magnetic interactions was accomplished by dehydrating the chain compounds to afford two soft magnets with critical temperature Tc. and coercive field of 2 K and 35 G for 1 b and2.3 K and 20 G for 2b. respectively.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 01/04/20 alle ore 22:36:25