Dicarboxylate ligand-modulated assembly of new luminescent zinc(ii) coordination polymers with in situ formed tetrazole ligands: an experimental and theoretical study

Abstract

In situ hydrothermal reactions of Zn(NO₃)₂·6H₂O, NaN₃, and CPI with H₂DPA or H₂PYDC gave rise to two new zinc(II) coordination polymers, [Zn₃(IPT)₂(DPA)₂] (1) and [Zn₃(IPT)₂(PYDC)₂]·2H₂O (2) (CPI = 1-(4-cyanophenyl)imidazole, HIPT = 5-[4-(imidazol-1-yl)phenyl]tetrazole, H₂DPA = [1,1′-biphenyl]-2,2′-dicarboxylic acid and H₂PYDC = pyridine-2,4-dicarboxylic acid), which were characterized by elemental analysis, IR, TGA and single crystal X-ray diffraction. Complex 1 features a new two-dimensional metal–organic layer with (3,6)-connected kgd topology based on cationic [Zn₃(DPA)₂]²⁺ clusters and anionic IPT ligands and further forms a three-dimensional supramolecular architecture via weak C–H⋯O hydrogen-bond interactions. However, complex 2 exhibits a three-dimensional framework formed from cationic [Zn₃(PYDC)₂]²⁺ chains and anionic IPT ligands, displaying a rare tetranodal (3,3,4,4)-connected net with 3,3,4,4T76 topology. Interestingly, the IPT ligands display different conformations and coordination modes in 1 and 2 due to the effect of the ancillary dicarboxylate co-ligands. All these data indicated that the nature of the ancillary dicarboxylate co-ligands plays an important role in diversifying the resulting architectures. The luminescence properties and thermal stabilities of the two complexes have also been investigated. Finally, high level theoretical calculations were performed to examine the conformations and coordination modes of the IPT ligands as well as the photophysical properties of the two complexes.