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

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 103 srs (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.