Two new layered inorganic–organic hybrids: intercalation of 1,3,5-benzenetricarboxylate in lead bisphosphonate

Abstract

Hydrothermal reactions of N-benzyl-iminobis(methylenephosphonic acid), C 6H 5CH 2N(CH 2PO 3H 2) 2 (H 4L), with lead(II) carbonate in the presence of butane diacid resulted in a new layered lead(II) amino-bisphosphonate, namely, Pb 3L(H 2L)·1.5H 2O 1. When 1,3,5-benzene-tricarboxylic acid (H 3BTC) was used instead of butane diacid, a new layered lead(II) amino-bisphosphonate containing noncoordinated H 3BTC molecules, Pb 3(HL) 2·2(H 3BTC)·2H 2O 2 was isolated. Compound 1 crystallizes in the monoclinic space group P2 1/ c with cell dimensions of a=17.6776(14) Å, b=10.0111(8) Å, c=16.6017(13) Å, β=104.134(2)° and Z=4. Compound 2 crystallizes in triclinic space group P-1 with cell parameters of a=4.8797(4) Å, b=9.9736(7) Å, c=24.3631(17) Å, α=97.680(2)°, β=95.0000(10)°, γ=102.4340(10)° and Z=1. Both compounds feature a layered structure and have a same metal/ligand ratio of 3:2. Compound 1 contains two types of ligands with different charges, −2 and −4, respectively. The lead(II) ions are bridged by bisphosphonate ligands, resulting in a 〈100〉 layer. In compound 2, the interconnection of the lead(II) ions by bridging phosphonate groups resulted in a 〈001〉 layer, with the neutral H 3BTC ligand intercalated between two layers, forming hydrogen bonds with lattice water molecules, noncoordinated phosphonate or carboxylate groups. In both compounds, the phenyl groups of the ligands are orientated toward the interlayer space. TGA and IR spectra for both compounds have been also studied.