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

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 L^2–, 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. ESI-MS positive of 1–6 reveal 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 intergrals (H = –2JS₁.S₂ 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 diphenoxo bridge).