Polymeric dichlorido-bridged copper(II) offset stacked dimer coordination compounds and molecular spin stairs

Abstract

A family of oxygen coordinated dichlorido-bridged n-X-2-pyridone (1, n = 3, X = Cl; 2, n = 3, X = Br; 3, n = 4, X = Cl; 4, n = 4, X = Br; 5, n = 5, X = Cl; 6, n = 5, X = Br) Cu(II) offset stacked dimer compounds, denoted molecular spin stairs, have been prepared and analyzed by single-crystal X-ray diffraction (1–4), powder X-ray diffraction (1–6), and variable temperature magnetic susceptibility measurements (1–6). Ferromagnetism is dominant in all compounds with a weaker antiferromagnetic exchange present in 1–4. The ferromagnetic exchange correlates to increased twist angles which are defined by the extent of the tetrahedral distortion of the copper coordination sphere and the identity of the halogen on the ring. The compounds were qualitatively fit to a ferromagnetic Heisenberg chain model with a Curie-Weiss interchain correction. The general Hamiltonian used is of the form $H=-J\sum {\mathit{S}}_1{\mathit{S}}_2.$ The ratio of exchange energies denoted α $\left(\alpha =\frac{J_{\mathit{\text{FM}}}}{\left|J_{\mathit{\text{AFM}}}\right|}\right)$ ranges between 2.6 and 4.7. This family of compounds constitutes possible S = ½ Haldane-like materials.

Keywords:

• Low-dimensional magnetism
• Ferromagnetism
• Copper(II) dimer
• Molecular spin stair

Disclosure statement

There are no conflicts to declare.

Additional information

Funding

The authors are grateful to SEQENS for funds towards the purchase of the X-ray powder diffractometer, the National Science Foundation (IMR-0314773) towards the purchase of the MPMS SQUID magnetometer and for the purchase and installation of a helium recycling system (DMR-1905950), and the Kresge Foundation towards the purchase of both. The National Science Foundation also supported the purchase of the D8 Venture single-crystal diffractometer (CHE-2018870). MRG is grateful for support from the Frederick M. and Alice Murdock Research Fund.