Syntheses, Topological Structures, and Photoluminescences of Six New Zn(II) Coordination Polymers Based on Mixed Tripodal Imidazole Ligand and Varied Polycarboxylates

Abstract

Solvothermal reactions of the tripodal ligand 1,3,5-tris(1-imidazolyl)benzene (tib) and different polycarboxylates with zinc nitrate provided six new zinc(II) coordination polymers (CPs), namely, {[Zn8(tib)5(bdc)8(H2O)]·7DMF·18H2O}n (1), {[Zn3(tib)2(bpdc)3]·5H2O}n (2), {[Zn(tib)(pdac)]·1.5H2O}n (3), {[Zn6(tib)2(pdac)3]·DMA·2H2O}n (4), {[Zn2(tib)2(pma)]·4H2O}n (5), {[Zn2(tib)(Htib)(H2pma)(Hpma)]·2H2O}n (6) (H2bdc = 1,3-benzenedicarboxylic acid, H2bpdc = 4,4′-biphenyldicarboxylic acid, H2pdac = 1,2-phenylenediacetic acid, H4pma = pyromellitic acid, DMF = N,N′-dimenthylformamide, DMA = N,N′-dimethylacetamide). All of the complexes have been structurally characterized by single-crystal X-ray diffraction analyses and further characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). Single crystal X-ray diffraction analysis reveals that complex 1 exhibits a complicated self-catenating three-dimensional (3D) framework that could be decomposed to two interpenetrating (4,6)-coordinated sun1 nets with point symbol of {3·4·64}{3·46·52·64·72}2. Complex 2 is a 2-fold interpenetrating (3,4)-coordinated new topology sun2 with point symbol of {103}2{106}3. In complex 3, both the tib and pdac act as a bidentate bridging ligand and extend the tetrahedral Zn(II) centers to an interesting one-dimensional (1D) independent single-wall metal–organic nanotube (SWMONT). Differently, the tib and pdac become tridentate and bidentate linkers in complex 4, respectively, which extend the Zn(II) centers to the resulting 2-fold interpenetrating (3,4)-coordinated network with a srd topology and the point symbol is {63}2{64·92}3. Complex 5 is a (3,4)-coordinated self-penetrating network sun3 with point symbol of {103}{106}. This net could be further decomposed to two interpenetrating 3-coordinated 103srs (SrSi2) subnets by omitting the 2-coordinated pma linker, while complex 6 shows an undulated 2D 3,3L4 layer, which is interdigitated with each other to form a 3D supramoleular framework stabilized by hydrogen bonds. The structural and topological differences of the six CPs indicate that the auxiliary polycarboxylates and solvents play important roles in the formation of the final structures. Furthermore, the thermal stability and photoluminescence properties of the complexes were investigated.