Synthesis, crystal structure, magnetic properties and DFT calculations of a mononuclear copper(II) complex: Relevance of halogen bonding for magnetic interaction

• Published in: Inorganica Chimica Acta Vol. 482; pp. 395 - 401
• Main Authors: Silva, Cassiano P., Junior, Henrique C.S., Santos, Igor F., Bernardino, Alice M.R., Cassaro, Rafael A.A., Novak, Miguel A., Vaz, Maria G.F., Guedes, Guilherme P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2018; Elsevier Science Ltd
• Subjects: Antiferromagnetism; Chains; Chemical bonds; Coordination compounds; Copper; Copper compounds; Copper(II); Coupling (molecular); Crystal structure; Crystallography; DFT calculations; Divergence; Hydrogen bonds; Hysteresis; Magnetic fields; Magnetic properties; Magnetism; Pyrazole; Pyrazole ligands; Spin canting; Synthesis; Pyrazole ligands; Spin canting; DFT calculations; Copper(II); Magnetic properties
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2018.06.033

[Display omitted] •Mononuclear copper(II) compound containing a pyrazol-based ligand.•Short contact N–H⋯Cl plays a key role to the magnetic properties.•Magnetic hysteresis and divergence between ZFC-FC curves.•Spin canting phenomena. The synthesis, crystal structure, magnetic properties and DFT calculations of a new mononuclear copper(II) complex containing a pyrazole-based ligand are reported. In the crystal structure of the [CuCl2L2] complex (L = Ethyl 5-amino-1-(4-methoxyphenyl)-1H-pyrazole-4-carboxylate), a network of hydrogen bonds connects the molecular units in the crystal packing. The magnetic studies revealed predominant antiferromagnetic interactions among molecular units. Since there are multiple intermolecular contacts that can act as pathway for magnetic interactions, DFT calculations revealed the fundamental role of N–H⋯Cl short intermolecular contacts in magnetic behavior. Supported by DFT calculation, the magnetic data above 7.0 K was modeled as a regular Heisenberg chain (H=-2J∑i=1n-1S→Ai·S→Ai+1) resulting in a weak magnetic coupling constant (J) of −2.6 cm−1. Below this temperature, an unusual magnetic behavior for mononuclear copper(II) complexes was observed: divergence between zero-field cooled (ZFC) and field cooled (FC) magnetic susceptibilities and magnetic hysteresis cycles at low temperatures attributed to spin canting along the chain.