The supramolecular assembly of tetraaqua-(pyridine-2,5-dicarboxylato)- copper(II) complex: Crystal structure, TD-DFT approach, electronic spectra, and photoluminescence study

The copper(II) complex, {[Cu(2,5-pdc)(H2O)4]·H2O} (1) [2,5-pdc = pyridine-2,5-dicarboxylate], has been synthesized and characterized by elemental analysis, IR spectroscopy, and X-ray crystallography. The metal shows a distorted octahedral coordination sphere and in solid state the complex forms a 3-D supramolecular network via hydrogen bonding and off-center anti-parallel π–π stacking interactions between py rings. At room temperature, 1 exhibits fluorescence in methanolic solution [λex = 226 nm, λem = 309, 330, and 341 nm]. The geometry optimization at the B3LYP/LanL2DZ level led to a five-coordinate copper having a distorted square pyramidal geometry. The electronic spectrum of this compound is compared with the results obtained by employing density functional theory (DFT) and time dependent density functional theory calculations.