Two lead(II) 2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate complexes exhibiting different topologies and fluorescent properties

The reactions of PbCl2 with 2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid (H3iso) gave two complexes [Pb(H2iso)2(H2O)]n (1) and [Pb(Hiso)(H2O)]n (2), which were characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and single crystal X-ray diffraction analysis. The two complexes display different topologies. 1 shows a three-dimensional framework with the Schläfli symbol (4.85)(4.82) no matter if the weak Pb–O bonds are included or not. However, 2 presents a 3,3-connected two-dimensional sheet with the Schläfli symbol (4.82)(4.82) based on the calculation of only the normal Pb–O bonds and a 5,5-connected 3D network with the Schläfli symbol (415.64)(44.68.82) when the weak Pb–O bonds are also included. The fluorescent studies reveal an emission attributed to intraligand emission for 1 and an emission assigned to LMCT for 2.