Different Temperature Dependence of Magnetic Susceptibility of Different Molecular Complexes of Copper (II) with 7-Hydroxy-4-methyl-5-aza-hept-4-en-2-on

Abstract

Abstract Two principally different molecular structures in the crystalline state are known from the copper (II) complex with 7-hydroxy-4-methyl-5-aza-hept-4-en-2-on. The magnetic susceptibilities of three forms of this compound [α-(CuEIA) 4 , β-(CuEIA) 4 , and β-(CuEIA) 4 ·2 C 6 H 6 ] have been measured in the temperature range 2.6-300 K. The results indicate that principally different molecular structures correspond to principally different magnetic properties. While the α-form shows antiferromagnetic spin coupling in the S′ = 0 ground state, the electrons in the β-form are coupled ferromagnetically in the S′ = 2 ground state. A fitting procedure of a theoretical equation based on the isotropic HDVV-model led to a satisfactory agreement between calculated and experimental data for α-(CuEIA) 4 and β-(CuEIA) 4 , while this was not possible for β-(CuEIA) 4 ·2C 6 H 6 . The exchange parameters obtained for α-(CuEIA) 4 (g=2.13, J 12 = -17cm -1 , J 13 =+3.5cm -1 , and N a =60-10 -8 cgs-emu) are in good agreement with the values given by Ginsberg et al. For β-(CuEIA) 4 a weak antiferromagnetic intercluster interaction could be determined at low tempera­tures. The fitting procedure yielded the following values: g=2.05, J 12 =-6.4 cm -1 , J 13 =+24.2 cm -1 , N a =10·10 -6 cgs-emu, ⊖=-0.27°.