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Self-assembly reaction of Pb(NO3)2 with thiophene-2, 5-dicarboxylic acid (H2TDC) led to an acentric three-dimensional (3D) metal-organic framework under solvothermal conditions, namely, Pb(TDC) (1). The 3D framework of 1 is a pillared-layer structure with the I2O1 type which is composed of a 2D inorganic Pb–O–Pb substructural layer and two independent μ6-TDC2- anions pillars. This 3D framework shows a six-connected pcu topological net according to the topological analysis. Compound 1 crystallizes in an acentric space group and displays potential ferroelectric property which could be due to the swing of the thiophene rings. The remnant polarization (Pr), coercive field (Ec) and saturation spontaneous polarization (Ps) of 1 are ca. 0.034 μC cm−2, 15.7 kV cm−1 and 0.0997 μC cm−2, respectively. Among the H2TDC-based MOFs, the present compound is the first example which shows ferroelectric property. In addition, 1 also exhibits photoluminescent property which can be attributed to ligand-to-metal charge transfer.

Our systematic exploration of chainlike borate in the hybrid templated borate systems has led to three new borates, namely, [GaTETA]·[B5O8(OH)2]·H2O, [InTETA]·[B5O8(OH)2]·1.5H2O, and [Cd(1,2-dap)]·[B6O11(OH)2]·H2O. The structures of the three borates were determined by single-crystal X-ray diffraction. [Cd(1,2-dap)]·[B6O11(OH)2]·H2O represents the first example of chainlike borate containing Cd2+ transition metal cations and [B6O11(OH)2] cluster. [GaTETA]·[B5O8(OH)2]·H2O is isostructural with [InTETA]·[B5O8(OH)2]·1.5H2O, whose structure features a one-dimensional (1D) polyatomic chain constructed of MO2N4 octahedron and [B5O8(OH)2] groups, such chains are further bridged by HBs resulting in a three-dimensional (3D) supermolecular network. Optical and luminescent property measurements have also been performed on the three compounds. Only fluorescence intensity of [GaTETA]·[B5O8(OH)2]·H2O decreased fiercely with temperature increase. Besides, the band gap of [GaTETA]·[B5O8(OH)2]·H2O and its isomer [InTETA]·[B5O8(OH)2]·1.5H2O and [Cd(1,2-dap)]·[B6O11(OH)2]·H2O are very distinct from each other, it may indicate that optical and luminescent property of hybrid borate can be manipulated by adjusting of polyatomic cluster and metallic ion.

A new hydrated borate compound, [NH3CH2CHCH3NH3]][B(8)O11(OH)(4)].H2O 1, has been synthesized in the presence of 1,2diaminopropane acting as a structure-directing agent under mild conditions. Its structure was determined by single crystal X-ray diffraction and further characterized FTIR, elemental analysis, powder X-ray diffraction and thermogravimetric analysis. Compound I crystallizes in the monoclinic system, space group P21/c (No. 14), a = 10.0787(7)angstrom, b = 8.8482(6) angstrom, c = 19.3097(4) angstrom, beta = 91.352(6)degrees, V = 1721.53(2)angstrom(3), and Z = 4. The structure consists of infinite open-branched borate chains constructed from [B3O6(OH)] units, onto which the [B5O7(OH)(3)] groups are grafted. It represents the first example of one-dimensional borate templated by an organic amine. The adjacent borate chains are further linked together by extensive hydrogen bonds to form a 3D supramolecular network. The diprotonated organic amines and guest water molecules are filled in the free space of the hydrogen-bonded network and interact with the inorganic framework by extensive hydrogen bonds. (C) 2007 Elsevier Inc. All rights reserved.