Ligand-Induced Variations in Symmetry and Structural Dimensionality of Lead Oxide Carboxylates

Abstract

Four new lead oxide carboxylates have been prepared through solvothermal reactions between lead oxide and substituted benzoic acids. In these extended inorganic hybrids, edge-sharing Pb 4 O tetrahedra form 1-D inorganic substructures that are further coordinated by the carboxylate ligands. In two isostructural phases, Pb 2 O(C 7 H 4 (CH 3 )O 2 ) 2 ·0.25(H 2 O) and Pb 2 O(C 7 H 4 BrO 2 ) 2 ·0.23(C 2 H 5 OH), distorted Pb 4 O tetrahedra produce helical Pb 2 O 2+ chains. The 1-D chains in these structures are coordinated by p -toluate and 4-bromobenzoate ligands, respectively. Right- and left-handed helices are related through inversion, and the structures crystallize in the centrosymmetric I 4 1 / a space group. In Pb 2 O(C 7 H 4 O 3 ), linear Pb 2 O 2+ chains are linked into 2-D layers by salicylate ligands, resulting in the achiral, polar space group Fdd 2. In Pb 3 O 2 (C 7 H 3 FO 3 )·0.71(H 2 O), linear Pb 3 O 2 2+ double chains are linked into layers by 4-fluorosalicylate ligands. The compound crystallizes in the chiral, noncentrosymmetric space group P 2 1 . For each of the ligands in the new structures as well as in four previously reported structures, a ratio of the noncoordinating to coordinating volumes has been calculated. This ligand volume ratio shows a clear inverse correlation with the overall dimensionality of the lead oxide carboxylates. The analysis encompasses 1- to 3-D structures and ligands of differing denticities. Structures were determined through single-crystal X-ray diffraction, and the new compounds were further characterized via powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and elemental analysis.