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

摘要

The first linear bis(chlorido)-bridged Cu(II) compound with the ligand 2-amino-5-nitropyrimidine (abbreviated as anpyr), [Cu(_-CI)2(anpyr)2],,, 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) _ and two nitrogen atoms of two trans-located anpyr ligands with a Cu-N distance of 2.068(2) _. The apical positions of the distorted octahedral geometry are formed by two CI anions of a neighbouring unit with a distance of 2.8690(8) _. The Cu-CI-Cu angle is 94.75(3)°, while the Cu-Cu distance is 3.791 A. The Cu-bis-_-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) _, 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 CI distance 3.248(2) _. 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)).