A unique Cu(II) bis(chlorido)-bridged linear chain compound with 2-amino-5-nitropyrimidine as a bifunctional axial ligand: Synthesis, characterization, crystal structure and hydrogen-bonding system

The first linear bis(chlorido)-bridged Cu(II) compound with the ligand 2-amino-5-nitropyrimidine (abbreviated as anpyr), [Cu(μ-Cl)2(anpyr)2]n, has been synthesized and fully characterized by spectroscopy, EPR and X-ray structure analysis. The basal plane around the Cu(II) ion is formed by two chloride anions with a Cu–Cl distance of 2.2513(6) Å and two nitrogen atoms of two trans-located anpyr ligands with a Cu–N distance of 2.068(2) Å. The apical positions of the distorted octahedral geometry are formed by two Cl anions of a neighbouring unit with a distance of 2.8690(8) Å. The Cu–Cl–Cu angle is 94.75(3)°, while the Cu–Cu distance is 3.791 Å. The Cu–bis-μ-chlorido-Cu array provides in this way a 2D linear chain. A neighbouring pair of symmetry-related polynuclear chains is linked through hydrogen bonds with a N···N distance 3.027(3) Å, forming into a kind of Watson–Crick-like pair of hydrogen bonds. Another H-bond is formed by the amine nitrogen to one of the chloride anions with a N···Cl distance 3.248(2) Å. The EPR powder spectrum appears as rhombic with g1 2.20, g2 2.12; g3 2.05, with unresolved hyperfine splittings. Analysis of the magnetic susceptibility measurements, recorded from 2 to 300 K, indicates a very weak antiferromagnetic interaction between the metal ions (J = −2 cm−1).