Structure of cyano-bridged Eu(III)—Co(III) bimetallic assembly and its application to photophysical verification of photomagnetic phenomenonDepartment of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
E-mail: akitsu@chem.keio.ac.jp Received: 22 November 2006 Revised: 13 January 2007 Accepted: 15 January 2007 Abstract: New crystal structure of Eu(DMF)4(H2O)3Co(CN)6·H2O (DMF = N,N′-dimethylformamide) (Eu-Co) has been determined to be monoclinic, P2(1)/n, a = 19.796(12) Å, b = 8.862(11) Å, c = 17.525(10) Å, β = 96.26(5)°, V = 3056(5) Å3, Z = 4. The Eu(III) ion adopts an antiprismatic eight-coordination and forms a cyano bridge with r(Eu-N) = 2.496(7) Å and Θ(Eu-N-C) = 165.7(7)° to the Co(III) ion. The complex exhibits some common features with the Eu-Fe complex. Diffuse reflectance electronic spectra and magnetic susceptibility of Eu-Cr, Eu-Mn, Eu-Fe, and Eu-Co complexes were compared. By substituting the metal ions, both electronic and structural features affected the charge transfer bands and superexchange interactions concerning cyanide ligands. In addition, only Eu-Co exhibited 5 D 0 → 7 F 2 and 5 D 0 → 7 F 1 luminescence bands at 16300 cm−1 and 16900 cm−1, respectively at 298 K (λex = 360 nm (27000 cm−1)), because quenching by cyano-bridged ions did not prevent Eu(III) ion from exhibiting emission. Thus, only Eu-Co may be suitable for verification of an assumption of mechanism concerning drastic photoinduced magnetic changes for Nd-Fe. Merely small decrease of magnetization was observed for Eu-Co after UV light irradiation at 2.0 K. This result was attributed to slight structural changes around cyano bridges without transitions of spin states. Keywords: europium(III) - cobalt(III) - crystal structure - magnetism - spectroscopy Full paper is available at www.springerlink.com. DOI: 10.2478/s11696-007-0019-2
Chemical Papers 61 (3) 194–198 (2007) |
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