Modulated preparation and structural diversification of metal–organic frameworks based on 4,4′,4″-(1H-imidazole-2,4,5-triyl)tripyridine ligand

• Four MOFs with Htpim have been synthesized and characterized.
• Complexes of Htpim are tunable through controlling reaction conditions.
• Fluorescence quenching phenomena of 1–2 are observed due to effects of CuI or CuII.
• Intense luminescent emissions of 3–4 are attributed to the LLCT of Htpim.

Four metal–organic frameworks with 4,4′,4″-(1H-imidazole-2,4,5-triyl)tripyridine (Htpim), namely {[Cu4(tpim)4](DMAC)(H2O)3}∞ (1), {[Cu(H2tpim)2(H2O)2](NO3)4(H2O)2}∞ (2), {[Zn(Htpim)2(H2O)2](NO3)2(H2O)5}∞ (3) and {[Zn(Htpim)(NO3)(H2O)](NO3)}∞ (4) (DMAC = N,N-dimethylacetamide), have been prepared under solvothermal conditions. Single crystal X-ray diffraction analysis indicates that the ligand Htpim adopts ionized form in 1, protonated form in 2, and primary form both in 3 and 4, respectively, with three types of binding modes including μ2-Npy,Npy mode in 2 and 3, μ3-Npy,Npy,Nim mode in 1 and μ3-Npy,Npy,Npy mode in 4. Different network structures, a 2D 3,4-connected {4.62}2{42.62.82} network of 1, a 1D linear chain of 2 and 3, and a 2D 63 framework of 4, were observed and attributed to different synthetic conditions or metal ions. Nitric acid was used not only to adjust the pH value of reaction system, but also to act as a coordination component in 2–4. Furthermore, luminescent properties have also been studied for these four complexes.

Four MOFs, showing 1D linear chain, 2D {4.62}2{42.62.82} network and 2D 63 network, have been successfully constructed by Htpim. The discrepancy of synthetic routes and metal-coordination preferences facilitates the production of the final crystalline materials with distinct structures. Moreover, the fluorescence quenching phenomenon of 1 and 2 are observed due to effects of CuI or CuII ions. Intense luminescent emissions of 3 and 4 are attributed to the LLCT of Htpim.Figure optionsDownload as PowerPoint slide