High-field EPR study and crystal and molecular structure of trans-RSSR-[CrCl2(cyclam)]nX (X=ZnCl4 2-, Cl- and Cl-.4H2O.0.5HCl).
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-[CrCl(2)(cyclam)](2)ZnCl(4), 1, the red-purple trans-RSSR-[CrCl(2)(cyclam)]Cl, 2, and the red-purple trans-RSSR-[CrCl(2)(cyclam)]Cl.4H(2)O.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 1, g= 2.01, D=-0.305 cm(-1), E= 0.041 cm(-1) and lambda=|E/D|= 0.1396; for 2, g= 2.01; D=-0.348 cm(-1), E= 0.042 cm(-1) and lambda=|E/D|= 0.1206 and for 3, g= 1.99, D=-0.320 cm(-1), E= 0.041 cm(-1) and ambda=|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.
Division de Estudios de Posgrado, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Coyoacan, D. F. 04510, Mexico. mest@servidor.unam.mx
Alejandro
A
Solano-Peralta
Martha E
ME
Sosa-Torres
Marcos
M
Flores-Alamo
Hassane
H
El-Mkami
Graham M
GM
Smith
Ruben A
RA
Toscano
Takato
T
Nakamura