Ferromagnetic coupling in copper benzimidazole chloride: structural, mass spectrometry, magnetism, and DFT studies - zeng's paper

The quasi-square planar CuII(Hmbm)Cl2 (CBC, Hmbm = 1-methyl-1H-benzo[d]imidazol-2-yl)methanol) are arranged in a pseudo orthogonal way to form Cl-bridged chains and further π···π interactions resulted in distorted hexagonal layers. DFT calculations reveal bond strength order Cu-Cl> Cu-O/N >> Cu···Cl. ESI-MS reveal several small fragments from CBC but oligomeric [CuII 2], [CuII 3] and [CuII 4] for non-zero in source energies. MS indicates the occurrence of several chemical processes, viz. splitting of the ligand, oligomerization, redox reaction of alcohol to aldehyde and CuII to CuI. Gibbs free energies for the fragments were estimated using DFT. The magnetic susceptibility was modeled with ferromagnetic coupling J(Cu-Cl2a···Cu) = +0.99(30) cm-1 and J’(π···π) = +0.35(16) cm-1 and g = 2.38(2). HF-EPR determined the anisotropic g-values, gx = 2.24, gy = 2.16, and gz = 2.09, and hyperfine constant of Az = 450 G. DFT calculations from crystal structure data found J(Cu-Cl2a···Cu) of +3.6 at 296 K and +4.1 cm-1 at 90 K, dominates the magnetic properties, while J’(π···π) = 0.04 cm-1 is negligibly small.