A series of novel Pb(ii) or Pb(ii)/M(ii) (M = Ca and Sr) hybrid inorganic–organic frameworks based on polycarboxylic acids with diverse Pb–O–M (M = Pb, Ca and Sr) inorganic connectivities

Abstract

Solvothermal reactions of Pb(NO₃)₂ with aromatic polycarboxylic acids and the alkaline or alkaline earth metal nitrates led to six novel homo- or heterometallic lead(II)/carboxylate inorganic–organic hybrid materials, [Pb(p-BDC)(μ₂-DMSO)] (1), [PbCa(m-BDC)₂(μ₁-DMSO)] (2), [PbCa(OH-m-BDC)₂(CH₃OH)₂] (3), (Me₂NH₂)[PbSr(OH-m-BDC)(O-m-BDC)] (4), [Pb(SDBA)] (5), and [PbCa(SDBA)₂(μ₁-DMSO)₂] (6) (p-H₂BDC = 1,4-benzenedicarboxylate, m-H₂BDC = 1,3-benzenedicarboxylate, OH-m-H₂BDC = 5-hydroxy-1,3-benzenedicarboxylate, and H₂SDBA = 4,4′-sulfonyldibenzoic acid). These hybrids have been fully characterized by single crystal X-ray diffraction, XRD, TGA, IR, UV-vis, elemental analysis and photoluminescence spectra. They are all three-dimensional structures except for 6, which displays a 2D layer structure. Topology analysis reveals that complexes 1–6 manifest dia, pcu, sne, hex, sev, and (4,4)-topological nets, respectively. Moreover, they exhibit diverse inorganic connectivities which have not been observed for the lead(II)/carboxylate systems, e.g. the 1D Pb–O–Pb chains in 1 and 5, the 2D Pb–O–Ca layer in 2, the 1D Pb–O–Sr chain in 4, and the 1D Pb–O–Ca chains in 3 and 6. The luminescent properties of these hybrid materials, the NLO property of 3 as well as the methane sorption property of 5 have also been investigated.