Direct synthesis of PbO nanoparticles from a lead(II) nano coordination polymer precursor: synthesis, crystal structure, and DFT calculations of [Pb₂(dmp)₂(μ-N₃)₂(μ-ClO₄)₂]n with the First Pb₂-(μ- ClO₄)₂ unit

Abstract

Nanostructures of a new coordination polymer of divalent lead with the ligand 2, 9-dimethyl-1, 10-phenanthroline (dmp) containing the first Pb2-(mu-ClO4)2 motif, [Pb2(dmp)2(mu-N3)2(mu-ClO4)2]n (1), was synthesized by a sonochemical method that produces the coordination polymers at nano size. The new nanostructure was characterized by scanning electron microscopy, X-ray powder diffraction, IR, 1H NMR and 13C NMR spectroscopy, and elemental analysis. Compound 1 was structurally characterized by single-crystal X-ray diffraction and the single-crystal X-ray data shows that the coordination number of PbII ions is six, (PbN4O2), with two N-donor atoms from aza-aromatic base ligands and four O-donors from two perchlorate anions and two N-donors from two azide anions. It has a "stereo-chemically active" electron lone pair, and the coordination sphere is hemidirected. The supramolecular features in these complexes are guided and controlled by weak directional intermolecular interactions. The chains interact with each other through pi-pi stacking interactions creating a 3D framework. The structure of the title complex was optimized by density functional theory calculations. Calculated structural parameters and IR spectra for the title complex are in agreement with the crystal structure. The PbO nanoparticles were obtained by thermolysis of 1 at 180 degreesC with oleic acid as a surfactant. The average diameter of the nanoparticles was estimated by the Scherrer equation to be 23 nm. The morphology and size of the prepared PbO samples were further observed using SEM.