Structural diversity of coordination polymers assembled from adamantane dicarboxylates and conformational bis-triazole ligand

Abstract

A series of new coordination polymers have been hydrothermally synthesized by the combination of adamantane dicarboxylates and long conformational bis-triazole ligand with Zn(II)/Co(II)/Cd(II) ions, formulated as {[Zn(ADC)(btmb)]·3H₂O}_n (1), {[Co₂(ADC)₂(btmb)₂]·H₂O}_n (2), {[Cd(ADA)(btmb)(H₂O)]·H₂O}_n (3), {[Zn(ADA)(btmb)_0.5]·H₂O}_n (4), {[Co₂(ADA)₂(btmb)₂]·H₂O}_n (5), [Cd₂(ADA)₂(btmb)₂]_n (6) (H₂ADC = 1,3-adamantanedicarboxylic acid, H₂ADA = 1,3-adamantanediacetic acid and btmb = 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl). All crystalline polymers have been structurally characterized by single-crystal X-ray diffraction, elemental analysis, IR, TGA and XRD. Crystal structural analysis reveals that complex 1 has a 1D infinite tubular structure. Complexes 2 and 3 possess the similar 2D undulating layer structure with (4⁴)-sql network. Interestingly, only the polymer 2 displays a 2-fold parallel interpenetrating 2D → 2D framework. Complex 4 presents a binodal (3,4)-connected V₂O₅-type net. While both 5 and 6 feature binodal (3,5)-connected networks. In particular, intermolecular forces have important effects on the formation and strengthening of the supramolecular architecture. Structural diversities indicate that distinct adamantane dicarboxylates, conformational bis-trizaole ligands and the nature of metal ions play crucial roles in modulating structures and topologies of the final polymers. Moreover, the thermal stability of crystalline sample 1 has been investigated through TGA and VT-XRD measurements. The luminescent properties of 1, 3, 4 and 6 have been studied.