A pyrazolate-bridged cyclic tetranuclear copper(II) complex : synthesis, crystal structure and magnetic properties

• Main Authors: Zhang, Hua, Fu, Degang, Ji, Feng, Wang, Guoxiong, Yu, Kaibe, Yao, Tianyang
• Other Authors: School of Materials Science & Engineering
• Format: Article
• Language: English
• Published: 2012
• Subjects: DRNTU::Science::Chemistry::Inorganic chemistry::Synthesis
• Online Access: https://hdl.handle.net/10356/95681; http://hdl.handle.net/10220/8334
• Institution: Nanyang Technological University

A new pyrazolate-bridged tetranuclear copper(II) complex [{CuL(H2O)}4]·12H2O (H2L = 5-methoxycarbonylpyrazole-3-carboxylic acid) was synthesized and its crystal structure determined. The molecule has C2 symmetry and consists of four copper atoms bridged by four planar L ligands through the nitrogen atoms of the pyrazole groups to form a (–Cu–N–N–)4 12-membered ring. The co-ordination of each copper is distorted square planar. The basal plane of each copper atom is nearly parallel to a neighbouring pyrazole plane and perpendicular to another neighbouring pyrazole plane. In the crystal there is a hydrogen-bond network between water molecules and carboxylate groups which may control the packing. The magnetic properties of the complex have also been investigated down to 5 K. The fitting of the experimental data using a Heisenberg Hamiltonian shows that the exchange interaction between the copper atoms propagated through the monopyrazolate bridge is antiferromagnetic with J=–12.34 cm^–1. The reason for this small value relative to those in di-µ-pyrazolato-dicopper(II) complexes is discussed.