摘要

This work presents the systematic investigation on the reactions of Cd(II) ions with various aromatic polycarboxylic acids in organic solvents under solvothermal conditions. By using salts such as LiNO3 or NH4NO3 as templates, eight new metal-polycarboxylate frameworks, namely, (Me2NH2)[CdLi(p-BDC)(2)]center dot CH3OH (1), (Me2NH2)(2)[Cd(p-BDC)(2)]center dot(Me2NH) (2), (Me2NH2)[CdLi(m-BDC)(2)] (3), (Me2NH2)[Cd(OH-m-HBDC)(OH-m-BDC)]center dot DMF center dot CH3OH center dot H2O (4), [Cd1.5Li(5-Bu-t-m-BDC)(2)(DMF)(2)] (5), (Me2NH2[CdLi(OBA)(2)] (6), (Me2NH2)[CdLi(SDBA)(2)]center dot DMF center dot CH3OH (7), and (Me2NH2)[Cd-3(H2O)(3)(OH)(SDBA)(3)](8) (p-H2BDC = 1,4-benzenedicarboxylate, m-H2BDC = 1,3-benzenedicarboxylate, OH-m-H2BDC = 5-hydroxy-1,3-benzenedicarboxylate, 5-Bu-t-m-H2BDC = 5-tert-Butyl-1,3-benzenedicarboxylate, H(2)OBA = 4,4'-oxybis(benzoic acid) and H(2)SDBA = 4,4'-sulfonyldibenzoic acid) have been isolated in good yields from the reactions of corresponding polycarboxalate ligands with Cd(II) ions in DMF(or DMAC) at 160 degrees C. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric analyses. Compounds 1, 2, 3, 5, and 6 are three-dimensional frameworks, of which 1 features in unprecedented 6-connected topological network, while 2 and 3 have structures with qtz and pcu topologies, respectively. Both 4 and 7 have a two-dimensional layer framework, whereas 8 exhibits a one-dimensional chain structure. Compounds 1, 3, 6, and 7 are the first example of Cd(II)/Li(I) heterometallic coordination polymers. in which the Li(I) ions bond to carboxylate ligands and also are involved in the extending of polymer. All of these compounds except 1 and 5 crystallize in acentric (or chiral) space groups mid the bulk materials for 3 4, and 0 display strong powder second harmonic generation efficiencics, approximately 4, 2, and 5 times that of a potassium dihydrogen phosphate (KDP) powder. In addition, 4, 7, and 8 all have ferroelectric properties. The fluorescence properties and thermal stabilities Cor these compounds are also investigated.