Tetrahalidocuprate(II) complexes with substituted pyridinium ions: effects of halide substitution

Abstract

The Cu(II) complexes (H-5-FAP)₂CuBr₄ (1) and (H-2,3-dimpy)₂CuCl₄ (2) have been prepared and characterized structurally and magnetically (H-5-FAP = 2-amino-5-fluoropyridinium; H-2,3-dimpy = 2,3-dimethylpyridinium). They crystallize in the space groups P-1 and Pbcn, respectively, in comparison to their halido counterparts (H-5-FAP)₂CuCl₄ (1a) and (H-2,3-dimpy)₂CuBr₄ (2a) which crystallize in the space groups P2₁/c and P2₁/n. The differences in crystal packing, resulting in part from the difference in distortion of the CuX₄²⁻ ions, create different magnetic lattices. Data for 1 were fit to the strong-rail ladder model resulting in a Curie constant of 0.400(8) emu-K/mol-Oe, J/k_B-rail = −5.77(1) K and J/k_B-rung = 3.17(3) K. Data for 2 were fit to the Curie-Weiss law resulting in a Curie constant of 0.398(1) emu-K/mol-Oe and θ = −0.11(4) K, indicating a virtual lack of magnetic exchange interactions. The structures and magnetic properties are compared to literature compounds and general trends noted. The differences in the chloride/bromide ions in the structure lead to significant differences in the packing in the cases of both 1 and 2, which result in differences in the antiferromagnetic exchange in both complexes and, in the case of 2, versus 2a, an elimination of the antiferromagnetic properties.

KEYWORDS:

• Copper(II)
• Magnetism
• X-ray Structures
• Pyridinium ions

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors acknowledge financial assistance from the National Science Foundation (NSF) for grants to purchase the SQUID magnetometer (IMR-0314773) and toward the purchase and construction of a helium recycling system (DMR-1905950). Contributions from SEQENS toward the purchase of the powder X-ray diffractometer and from the Kresge Foundation for the purchase of both the SQUID and X-ray diffractometer are also greatly appreciated.