Synthesis, structures and luminescent properties of new Pb(ii)/M(i) (M = K, Rb and Cs) frameworks based on dicarboxylic acids: A novel icosahedral Pb 6-M 6 SBU

Reactions of Pb(CH 3COO) 2·3H 2O, MNO 3 (M = K, Rb, and Cs) with m-H 2BDC (1,3-H 2BDC = 1,3-benzenedicarboxylic acid) in a mixed-solvent of DMF and methanol (v/v = 2/1) resulted in the formation of novel metal-organic frameworks [(Me) 4N] 2[Pb 6M 6(m-BDC) 9(OH) 2]·H 2O (1: M = K; 2: M = Rb; 3: M = Cs). With H 2SDBA (H 2SDBA = 4,4′-sulfonyldibenzoic acid), two new lead(ii) coordination polymers, [K 2Pb(SDBA) 2(μ 3-H 2O)]·3H 2O (4) and [Cs 2Pb 2(SDBA) 3(DMF)] DMF (5), were isolated. These complexes have been fully characterized by elemental analysis, PXRD, FTIR, TGA and single crystal X-ray diffraction. Compounds 1-3 are 3-D coordination frameworks built by a novel 12-metal heterometallic Pb 6-M 6 cage that extends topologically into an eight-connected hex network via isophthalic acid ligands. Compounds 4 and 5 are new 3-D lead(ii) MOFs constructed by ladder-like Pb(ii)/K(i)/SDBA 2- and rod-shaped Pb(ii)/Cs(i)/SDBA 2- motifs, respectively. The Pb(ii) ions in these complexes show different coordination geometries with various coordination numbers (5, 7 and 9). In addition, an ideal T-shaped μ 3-H 2O is observed in 4. The SDBA 2- ligands in 4 and 5 display three types of new coordination modes that have not been observed before. At room temperature, 1-3 exhibit strong emissions in the solid-state which can be attributed to ligand-to-metal charge transfer between the delocalized π bonds of carboxylate groups and p orbitals of lead(ii) centers. © 2012 The Royal Society of Chemistry.