Syntheses, crystal structures, magnetic properties and ESI-MS studies of a series of trinuclear CuIIMIICuII compounds (M = Cu, Ni, Co, Fe, Mn, Zn)

Abstract

Six trinuclear Cu^IIM^IICu^II compounds (M = Cu, Ni, Co, Fe, Mn, Zn) derived from the Schiff base ligand, H₂L (2 + 1 condensation product of salicylaldehyde and trans-1,2-diaminocyclohexane) are reported in this investigation. The composition of the metal complexes are [{Cu^IIL(ClO₄)}₂Cu^II(H₂O)]·2H₂O (1), [{Cu^IIL(ClO₄)}{Ni^II(H₂O)₂}{Cu^IIL}]ClO₄·CH₃COCH₃ (2), [{Cu^IIL(ClO₄)}{Co^II(CH₃COCH₃)(H₂O)}{Cu^IIL(CH₃COCH₃)}]ClO₄ (3) and isomorphic [{Cu^IIL(ClO₄)}₂M^II(CH₃OH)₂] (4, M = Fe; 5, M = Mn; 6, M = Zn). Two copper(II) ions in 1–6 occupy N₂O₂ compartments of two L²⁻ ligands, while the second metal ion occupies the O(phenoxo)₄ site provided by the two ligands, i.e., the two metal ions in both Cu^IIM^II pairs are diphenoxo-bridged. Positive ESI-MS of 1–6 reveals some interesting features. Variable-temperature and variable-field magnetic studies reveal moderate or weak antiferromagnetic interactions in 1–6 with the following values of magnetic exchange integrals (H = −2JS₁S₂ type): J₁ = −136.50 cm⁻¹ and J = 0.00 for the Cu^IICu^IICu^II compound 1; J₁ = −22.16 cm⁻¹ and J = −1.97 cm⁻¹ for the Cu^IINi^IICu^II compound 2; J₁ = −14.78 cm⁻¹ and J = −1.86 cm⁻¹ for the Cu^IICo^IICu^II compound 3; J₁ = −6.35 cm⁻¹ and J = −1.17 cm⁻¹ for the Cu^IIFe^IICu^II compound 4; J₁ = −6.02 cm⁻¹ and J = −1.70 cm⁻¹ for the Cu^IIMn^IICu^II compound 5; J = −2.25 cm⁻¹ for the Cu^IIZn^IICu^II compound 6 (J is between two Cu^II in the N₂O₂ compartments; J₁ is between Cu^II and M^II through a diphenoxo bridge).