A binuclear Cu(II) complex of a Schiff-base type polyhydroxyl ligand with asymmetrical phenoxo and methoxo bridges: crystal structure and magnetic properties

Abstract

[Cu₂(H₄L)(OCH₃)(H₂O)] · 2MeOH (1) has been synthesized from the reaction of 2-hydroxy-5-methylisophthalaldehyde, tris(hydroxymethyl)aminomethane and copper(II) perchlorate in methanol with the Schiff-base polyhydroxyl ligand (H₄L)³⁻ formed in situ. Single-crystal X-ray structure analysis of 1 reveals a binuclear structure with Cu(II) asymmetrically bridged by a methoxo and a phenoxo group with Cu–O–Cu bridging angles of 102.93(7)° and 100.17(7)°, respectively. The binuclear Cu(II) moieties utilize the coordinated and noncoordinated alkoxyl groups for formation of intermolecular hydrogen bonds, thus affording a 3-D supramolecular structure. Variable temperature magnetic measurements reveal strong antiferromagnetic coupling in 1 with the 2J-value of −729 cm⁻¹, which was mediated cooperatively by the methoxo and phenoxo bridges. Magneto-structural correlations are discussed based on the crystal structure.

Keywords:

• Crystal structure
• Cu(II) complex
• O-Bridge
• Magnetic properties

Acknowledgments

This work was supported by the Natural Science Foundation of China, the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, Program for New Century Excellent Talents in University, Innovation Program of Shanghai Municipal Education Commission, the Fundamental Research Funds for the Central Universities (WK1013002), SRFDP (20100074110015), and Science and Technology Commission of Shanghai Municipality (STCSM, contract No. 10dz2220500).