Cu(II) complexes with coordinated pyrazine-dioxide: pyrazine-bridged chains

Abstract

Two new pyrazine-bridged, linear chain complexes of Cu(II) of formula [Cu(pzdo)₂(H₂O)₂(pz)](A)₂·nH₂O [pzdo = pyrazine-N,N′-dioxide; pz = pyrazine; A = BF₄⁻ (1), ClO₄⁻ (2)] have been prepared. Single-crystal X-ray diffraction shows the Cu ions to be six-coordinate, pyrazine-bridged chains with trans-pairs of ancillary ligands. The pzdo molecules are coordinated through their oxygen atoms. The ClO₄⁻ and BF₄⁻ anions are each two-site disordered in the lattice. Further, there are partial occupancy water molecules in the lattice which are very weakly bound. The structures are stabilized by hydrogen bonds between the coordinated water molecules and the non-coordinated pzdo oxygen atoms as well as the anions. Variable temperature magnetic susceptibility data show antiferromagnetic interactions and the data were fit to the uniform chain model yielding J/k_B = −13.0(2) K and −11.8(2) K for 1 and 2, respectively [$\mathit{H}=-\mathit{J}\sum {\mathit{S}}_1•{\mathit{S}}_2$]. In addition, the structure of the serendipitously prepared compound [Cu(pz)(pzdo)(H₂O)₂](ClO₄)₂ (3) is described. The compound crystallizes as rectangular layers of Cu(II) ions bridged by pzdo (parallel to the a-axis) and pyrazine (parallel to the b-axis) with water molecules coordinated in the axial sites.

Graphical Abstract

Keywords:

• Cu(II)
• pyrazine
• pyrazine-dioxide
• antiferromagnetic

Acknowledgements

We are grateful for funds from PCI Synthesis, Inc. (now SEQENS) toward the purchase of the D8 Focus diffractometer, from the National Science Foundation (IMR-0314773) for purchase of the MPMS SQUID magnetometer, and from the Kresge Foundation for both instruments. Single crystal X-ray diffraction experiments for 1 and 2 were performed on a diffractometer at the University of Virginia funded by the NSF-MRI program (CHE-2018870).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We are grateful for funds from PCI Synthesis, Inc. (now SEQENS) toward the purchase of the D8 Focus diffractometer, from the National Science Foundation (IMR-0314773) for purchase of the MPMS SQUID magnetometer, and from the Kresge Foundation for both instruments. Single crystal X-ray diffraction experiments for 1 and 2 were performed on a diffractometer at the University of Virginia funded by the NSF-MRI program (CHE-2018870).