Synthesis, coordination modes, structures, and magnetic properties of halogen-substituted 2-hydroxypyridine copper(II) chloride coordination compounds

Abstract

A family of 6-X-2-hydroxyprydine/pyridone (6-X-2-HOpy/pyridone) Cu(II) compounds, [Cu(6-X-2-HOpy)₂Cl₂] (1 X = F; 2 X = Cl) and [(6-X-2-pyridone)CuCl(μ-Cl)]₂ (3 X = Cl; 4 X = Br), has been prepared. Solution-based infrared spectra displayed a correlation between tautomeric state, primarily driven by halogen identity, and coordination mode with neutral nitrogen coordination mode favored as Br ≪ Cl < F. The tautomeric state of 6-Cl-2-HOpy is influenced by metal ion concentration (M) with lactam concentration increasing as M increases. Compound 1 has F–F contacts less than the sum of the van der Waals radii but falls outside of the typical halogen bonding angle parameters, R–X•••Y = R–Y•••X = 138.2°. Compounds 1 and 2 exhibit weak antiferromagnetic exchanges, fit with a one-dimensional quantum Heisenberg antiferromagnetic linear chain (1D-QHAF) model and J/k_B = −1.99(1) K and −0.92(7) K, respectively. Compounds 3 and 4 exhibit a dominating ferromagnetic exchange and an antiferromagnetic exchange and were qualitatively fit to a ferromagnetic linear chain with an interchain interaction model. This model does not accurately represent the physical parameters of the system and was used to show that both exchanges exist and are nontrivial.

Keywords:

• Copper(II)
• magnetism
• coordination chemistry

Acknowledgments

The authors are also grateful to Dr. Louise Dawe for data collection of 2. MRG is grateful for support from the Frederick M. and Alice Murdock Research Fund.

Disclosure statement

No potential conflict of interest was reported by the authors.

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 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).