Additive Effects in the Formation of Fluorescent Zinc Metal–Organic Frameworks with 5‑Hydroxyisophthalate

Three new metal–organic frameworks (MOFs) are formed from the reaction of zinc with 5-hydroxyisophthalic acid (H3-5-hip) with a range of additives in dimethylformamide (DMF). The additives include water, pyridine, and [MenNH4–n]Cl (n = 0–4) and, through hydrogen bonding, have a marked effect on the formation and phase of any resultant MOF, often in a narrow range of substoichiometric concentrations. The three MOFs, [Me2NH2]­[Zn2(5-hip)­(H-5-hip)­(H2O)]·3.25DMF (1), α-[Me2NH2]2[Zn2(5-hip)2]·2DMF (2), and [Me2NH2]­[Me4N]2[Zn4(5-hip)2(H-5-hip2.5)]·3DMF (3), have solvent-accessible pores, and the flexibility of the MOFs allows relaxation from a porous state to minimize the void space on desolvation. Topological analysis of the frameworks reveals two previously unrecorded MOF topologies. Compounds 2 and 3 are fluorescent, while this property is absent in compound 1. We also present a revised structure for the closely related β-[Me2NH2]2[Zn2(5-hip)2]·2DMF (4).