Discrete and 1D coordination polymeric chloro-bridged copper(II) dimers exhibiting ferro- and antiferromagnetic exchange coupling: magneto-structural correlations and non-covalent interactions

Abstract

The synthesis and characterization of two 1D coordination polymers [Cu₂(MHL)Cl₂][ClO₄]₂·CH₃CN·THF (2·CH₃CN·THF) and [Cu₂(MPyPz)Cl₂][ClO₄]₂·CH₃CN (3·CH₃CN), having repetitive {Cu^II₂(μ-Cl)₂} units, of m-xylyl-based ligands with terminal tridentate (2-pyridyl)alkylamine (MHL = α,α'-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-m-xylene) and (2-pyridyl)alkylamine/pyrazole (MPyPz = α,α'-bis[N-(2-pyridylethyl)-N-(pyrazol-1-ylmethyl)amino]-m-xylene) coordination have been accomplished. X-ray crystallographic studies reveal that the copper(II) centers in the recently reported dichloro-bridged discrete {Cu^II₂(μ-Cl)₂} complex [{Cu(MeL)Cl}₂][ClO₄]₂ (1) of a tridentate (2-pyridyl)alkylamine ligand [MeL = methyl[2-(2-pyridyl)ethyl](2-pyridylmethyl)amine], 2·CH₃CN·THF, and 3·CH₃CN have distorted square-pyramidal geometry, sharing a base-to-apex edge with parallel basal planes. Variable-temperature susceptibility measurements in the range of 2-300 K reveal antiferromagnetic for 1|J (singlet-triplet energy gap) = -3.89 cm^-1] and 2·CH₃CN·THF (J = -1.84 cm^-1), and ferromagnetic for 3 ·CH₃CN (J = +6.27 cm^-1) coupling. The complexes provide useful information for the magneto-structural correlations.