posted on 2024-11-15, 00:43authored byAndrew D Burrows, Siobhan Chan, William Gee, Mary F Mahon, Christopher RichardsonChristopher Richardson, Viorica Sebestyen, Domenyk Turski, Mark Warren
Combining Zn(NO3)2·6H 2 O with a series of dicarboxylic acids in the presence of the N,N′-ditopic ligand di(4-pyridyl)-1H-pyrazole (Hdpp) results in a series of mixed-linker metal-organic frameworks (MOFs) that have been crystallographically characterised. The reaction with 1,4-benzenedicarboxylic acid (H2bdc) gives [Zn2bdc)2(Hdpp)2]·2DMF 1, which shows Zn2(μ-carboxylate)2(carboxylate)2 secondary building units (SBUs) linked by bdc ligands into sheets, and these are pillared by the Hdpp linkers into a doubly-interpenetrated three-dimensional network. The reaction with 1,4-naphthalene dicarboxylic acid (H2ndc-1,4) gives two products: [Zn2(1,4-ndc)2(Hdpp)]·4DMF 2a forms a three-dimensional network in which sheets, formed from Zn2(carboxylate)4 'paddle-wheel' SBUs being linked by 1,4-ndc, are connected together by Hdpp pillars, whereas [Zn(1,4-ndc)(Hdpp)]·DMF 2b forms a fourfold interpenetrated structure based on diamondoid networks with single zinc centres as nodes. The reaction with 1,3-benzenedicarboxylic acid (H2mbdc) produces [Zn(mbdc)(Hdpp)]·DMF 3, which forms a two-dimensional network with (4,4) topology in which ZnO2N2 nodes are interlinked by mbdc and Hdpp linkers. The reaction with 5-methyl-1,3-benzenedicarboxylic acid (H2mbdc-Me) also forms a two-dimensional network structure, [Zn2(mbdc-Me)2(Hdpp)2]·DMF 4, albeit wherein dicarboxylates bridge between zinc-dicarboxylate tapes, themselves formed by interlinking of Zn2(μ-carboxylate)2(carboxylate)2 SBUs similar to those in 1. Finally, the reaction with 2,6-naphthalene dicarboxylic acid (H2ndc-2,6) yields two crystalline species, both having the formula [Zn2(2,6-ndc)2(Hdpp)]·DMF 5a/5b and possessing infinite zinc-carboxylate chain motifs interlinked by both naphthalene rings and Hdpp linkers into a three-dimensional framework. In compounds 1, 2b, 3 and 4, the pyrazole NH groups are involved in hydrogen bonding that serves to link either interpenetrated networks or neighbouring sheets together. However, in 2a and 5a/5b the NH groups project into the pores of the framework enabling interactions with guest molecules.
History
Citation
Burrows, A. D., Chan, S., Gee, W. J., Mahon, M. F., Richardson, C., Sebestyen, V. M., Turski, D. & Warren, M. R. (2017). The impact of N, N ′-ditopic ligand length and geometry on the structures of zinc-based mixed-linker metal-organic frameworks. CrystEngComm, 19 (37), 5549-5557.