High-field EPR study and crystal and molecular structure of trans-RSSR-[CrCl2(cyclam)]nX (X=ZnCl4 2-, Cl- and Cl-·4H 2O·0.5HCl)
Por:
Solano-Peralta A., Sosa-Torres M.E., Flores-Alamo M., El-Mkami H., Smith G.M., Toscano R.A., Nakamura T.
Publicada:
1 ene 2004
Resumen:
For the first time, HF-EPR (94.5 GHz) spectroscopy has been used to determine crystal field parameters in chromium(III) coordination compounds. The large zero-field splitting parameters of the dark-green photochromic trans-RSSR-[CrCl2(cyclam)]2ZnCl4,1, the red-purple trans-RSSR-[CrCl2(cyclamy)Cl, 2 and the red-purple trans-RSSR-[CrCl2-(cyclan)]Cl·4H2O·0.5HCl, 3, where cyclam = 1,4,8,11-tetraazacyclotetradecane, have been obtained. A full analysis of EPR spectra at 94.5 GHz of diluted complexes 1,2 and 3 at 300 K revealed that they are extremely sensitive to D and E values. The rhombic distortion was precisely determined for each compound. For l, g = 2.01, D = -0.305 cm-1, E = 0.041 cm-1 and ? = |E/D| = 0.1396; for 2, g = 2.01; D = -0.348 cm-1, E = 0.042 cm-1 and ? = |E/D| = 0.1206 and for 3, g = 1.99, D = -0.320 cm-1, E = 0.041 cm-t and ? = |E/D| = 0.1281. The EPR study at 94.5 GHz at 10 K allowed us to confirm the sign of the D value for all compounds. These data indicate that at room temperature the crystal field is mainly rhombic and as the temperature decreases, the rhombicity of the D tensor increases slightly. These found differences between 1, 2 and 3 allowed us to establish the importance of the intermolecular interactions in the solid state due to different hydrogen bonding networks in their crystalline arrangement.
Filiaciones:
Solano-Peralta A.:
Division de Estudios de Posgrado, Facultad de Química, Ciudad Universitaria, Coyoacán, D. F. 04510, Mexico
Sosa-Torres M.E.:
Division de Estudios de Posgrado, Facultad de Química, Ciudad Universitaria, Coyoacán, D. F. 04510, Mexico
Flores-Alamo M.:
Division de Estudios de Posgrado, Facultad de Química, Ciudad Universitaria, Coyoacán, D. F. 04510, Mexico
El-Mkami H.:
School of Physics and Astronomy, University of St-Andrews, Fife, United Kingdom
Smith G.M.:
School of Physics and Astronomy, University of St-Andrews, Fife, United Kingdom
Toscano R.A.:
Institute de Química, Univ. Nac. Auton. de Mexico, Ciudad Universitaria, Coyoacán, D. F. 04510, Mexico
Nakamura T.:
Dept. of Mat. Sci. and Technology, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu, 432-8561, Japan
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