Pyridyl-imidazole copper compounds

Abstract

Three 4-(2’-pyridyl)imidazole (4-pyim) complexes of copper(II) have been synthesized and studied structurally and magnetically. The structures of [CuCl₂(4-pyim)] (1), [CuCl(4-pyim)₂]₂Cl₂(H₂O)₁₀ (2), and [Cu(CuCl₄)(4-pyim)₂][Cu(H₂O)(4-pyim)₂](CuCl₄)(H₂O)₄ (3) are reported. Single-crystal X-ray diffraction measurements show that 1 crystallizes in the monoclinic space group P2₁/n with a four-coordinate Cu(II) ion forming dimers via semi-coordinate bonds to bridging chloride ions. The structure of 1 shows the copper and chloride ions disordered over two sites. Compound 2 crystallizes in the triclinic space group P – 1 with five-coordinate Cu(II) ions in a highly distorted geometry between square pyramidal and trigonal bipyramidal. It has an extensive hydrogen bonding network created by 10 lattice water molecules, chloride ions, and nitrogen atoms in the ligands. Compound 3 crystallizes in the monoclinic space group Cc with both four- and five-coordinate Cu(II) ions present in the lattice; the five-coordinate Cu(II) ions display highly distorted geometries. All three compounds have hydrogen bonding and π-stacking interactions among the 4-pyim rings. Magnetic susceptibility data were collected on 1. Magnetic susceptibility data of 1 shows that it exhibits modest antiferromagnetic interactions which are best fit using a honeycomb model [(2J = −2.6(2) K), 2J’ = −1.6(2) K, $H=-2J\sum s_i{·s}_j$]. Disorder in the crystal structure decreases the rate of growth of the correlation length at low temperatures, lowering the temperature of the expected maximum in χ below the range of the data.

Keywords:

• Copper(II)
• heterocycle
• magnetism
• disorder

Data availability

CCDC 2217089 (1-100), 2217090 (1-153), 2217093 (1-303), 2217091 (2), and 2217092 (3) contain the supplementary crystallographic data (CIFs). These data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/ or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: [phone]; or E-mail: [email protected]. Figure SI-1 showing the comparison of the calculated and experimental powder patterns for 1.

Additional information

Funding

The authors are grateful for funds from SEQENS toward the purchase of the D8 Focus diffractometer, from the National Science Foundation (IMR-0314773) for the purchase of the MPMS SQUID magnetometer, and from the Kresge Foundation toward the purchase of both. In addition, we are grateful for funding from the NSF (CHE-2018870) toward the purchase of the PhotonIII diffractometer (U. Virginia). AAM is grateful for a summer fellowship from an anonymous donor.