Polynuclear 2D Copper(II) Complex of Pyrazine Containing Perchlorate As a Counter-Ion: Crystal Structure and DFT Calculations

A new polynuclear cationic complex of copper(II) (Cu(II)) with pyrazine as a ligand and perchlorate acting as a counter-ion was obtained. X-ray diffraction results accounted for a 2D polymer array of cations, in which the metal-ions were located on an ideal square-pyramidal coordination environment defined by four nitrogen atoms of pyrazines and one chloride. The polymer compound, which extended along the ab plane of the structure, showed Cu(II) displaced 0.9 Å from the plane defined by the N-atoms and chloride. Perchlorate ions were situated in cavities interacting with pyrazine by anion-π weak interactions. These low-energy bonds emerged as a consequence of the π-acidity of pyrazine upon coordination to Cu(II). Density-functional theory (DFT) calculations at the M06-2X level of theory using 6-31G(d) and 6-31+G(d) were conducted aimed at achieving an electronic description of selected properties of title complex. M06-2X/6-31G(d), in particular, proved to be an acceptable performer in dealing with geometric aspects keeping the computational cost very low.