Influence of the reaction conditions on the self-assembly of lead(II) 5-sulfosalicylate coordination polymers with chelating amine ligands

The synthesis and crystal structures of [Pb(Hssal)(2,2 '-bipy)(DMF)]n (1), [Pb(Hssal)(2,2 '-bipy)(H2O)]n (2), [Pb(Hssal)( phen)(DMF)]n (3), and [Pb-3(ssal)(2)(phen)(3)]n (4) were reported, where Hssal(2-) and ssal(3-) are doubly and fully deprotonated 5-sulfosalicylates, 2,2 '-bipy is 2,2 '-bipyridine, and phen is 1,10-phenanthroline. Compounds 1-4 were synthesized by the various reaction conditions, such as reaction temperature, molar ratio, and pH, and these structures are formed by infinite chains or layers where Pb-II ions are linked by Hssal2- or ssal3- bridges. Compound 1, which has a ladderlike chain, was formed in DMF/H2O. Compound 2 with a H2O molecule coordinated to PbII was prepared by a hydrothermal reaction. Compounds 3 and 4 were synthesized in a higher pH compared to compounds 1 and 2, containing the 2,2 '-bipy ligand. In 1-3,5-sulfosalicylates are doubly deprotonated, whereas in 4, 5-sulfosalicylate is fully deprotonated. Coordination modes of Hssal(2-) and ssal(3-) ligands in 1-4 are novel and are first reported in this presentation. Although compounds 1 and 3 have the same structural topology, their aromatic aromatic interactions are significantly different. The coordination spheres of Pb-II ions in 1 and 3 are holodirected, whereas in 2 and 4, they feature somewhat hemidirected properties with small holes or gaps. Compound 4 exhibits some interesting features that (1) there is not any solvent in the structure, (2) there are extensively aromatic aromatic stacking interactions among aromatic rings, and (2) there is also a weak interaction between Pb-II atoms in the trinuclear motif.