New Zn²⁺ Metal Organic Frameworks with Unique Network Topologies from the Combination of Trimesic Acid and Amino-Alcohols

A series of new Zn²⁺-trimesate (btc^3‑) metal organic frameworks (MOFs) has been isolated in the presence of various amino-alcohols under solvothermal conditions. Thus, the reaction of ZnCl₂ with trimesic acid (H₃btc) and the amino-alcohols triethanolamine (teoa), 2-(hydroxymethyl)­piperidine (hmpip), <i>N</i>-<i>tert</i>-butyldiethanolamine (tbdeoa), 1,4-bis­(2-hydroxyethyl)­piperazine (bhep), <i>N</i>-methyldiethanolamine (mdeoa), or 4-(2-hydroxyethyl)­morpholine (hem) in a 1.6:1:5.6 molar ratio in DMF afforded compounds (teoaH)₂[Zn­(btc)_1.33] (<b>MOAAF-1</b>) (MOAAF = metal organic amino-alcohol framework), (NH₂Me₂)₂(hmpipH)­[Zn₃(btc)₃] (<b>MOAAF-2</b>), (NH₂Me₂)­(tbdmaH)₂[Zn₃(btc)₃] (<b>MOAAF-3</b>) (tbdma = <i>N</i>-<i>tert</i>-butyl-dimethylamine), (NH₂Me₂)­(bhepH₂)­[Zn₃(btc)₃] (<b>MOAAF-4</b>), (NH₂Me₂)­[Zn₄(btc)₃(mdeoa)₂] (<b>MOAAF-5</b>), and (NH₂Me₂)­[Zn₄(btc)₃(hem)₂] (<b>MOAAF-6</b>), respectively. The compounds display 3D structures with relatively large cavities (4–10 Å) and high potential solvent-accessible areas (38–68% of the unit cell volumes). A number of novel structural features are revealed in the reported MOFs, such as unprecedented dinuclear [Zn₂(COO)₅]⁻¹ secondary building units (SBUs) and unique network topologies (e.g., in compounds <b>MOAAF-2</b>, <b>MOAAF-3</b>, <b>MOAAF-5</b>, and <b>MOAAF-6</b>). The amino-alcohols employed played a key role for the appearance of such novel structural features in <b>MOAAF 1</b>–<b>6</b> since they were found to act as bases responsible for the deprotonation of H₃btc, templates, and chelating ligands. Specifically, most of the compounds synthesized were shown to be templated by protonated amino-alcohols that are involved in hydrogen bonding interactions with the frameworks, whereas in two cases (compounds <b>MOAAF-5</b> and <b>MOAAF-6</b>) the amino-alcohols acted as chelating ligands affecting significantly the underline topology of the MOFs. The thermal stability and photoluminescence properties of the MOFs are also discussed. This work represents the initial systematic investigation on the use of combination of amino-alcohols and polycarboxylate ligands for the synthesis of new MOFs, demonstrating it as a powerful synthetic strategy for the isolation of novel MOFs

New Zn²⁺ Metal Organic Frameworks with Unique Network Topologies from the Combination of Trimesic Acid and Amino-Alcohols

A series of new Zn²⁺-trimesate (btc^3‑) metal organic frameworks (MOFs) has been isolated in the presence of various amino-alcohols under solvothermal conditions. Thus, the reaction of ZnCl₂ with trimesic acid (H₃btc) and the amino-alcohols triethanolamine (teoa), 2-(hydroxymethyl)­piperidine (hmpip), <i>N</i>-<i>tert</i>-butyldiethanolamine (tbdeoa), 1,4-bis­(2-hydroxyethyl)­piperazine (bhep), <i>N</i>-methyldiethanolamine (mdeoa), or 4-(2-hydroxyethyl)­morpholine (hem) in a 1.6:1:5.6 molar ratio in DMF afforded compounds (teoaH)₂[Zn­(btc)_1.33] (<b>MOAAF-1</b>) (MOAAF = metal organic amino-alcohol framework), (NH₂Me₂)₂(hmpipH)­[Zn₃(btc)₃] (<b>MOAAF-2</b>), (NH₂Me₂)­(tbdmaH)₂[Zn₃(btc)₃] (<b>MOAAF-3</b>) (tbdma = <i>N</i>-<i>tert</i>-butyl-dimethylamine), (NH₂Me₂)­(bhepH₂)­[Zn₃(btc)₃] (<b>MOAAF-4</b>), (NH₂Me₂)­[Zn₄(btc)₃(mdeoa)₂] (<b>MOAAF-5</b>), and (NH₂Me₂)­[Zn₄(btc)₃(hem)₂] (<b>MOAAF-6</b>), respectively. The compounds display 3D structures with relatively large cavities (4–10 Å) and high potential solvent-accessible areas (38–68% of the unit cell volumes). A number of novel structural features are revealed in the reported MOFs, such as unprecedented dinuclear [Zn₂(COO)₅]⁻¹ secondary building units (SBUs) and unique network topologies (e.g., in compounds <b>MOAAF-2</b>, <b>MOAAF-3</b>, <b>MOAAF-5</b>, and <b>MOAAF-6</b>). The amino-alcohols employed played a key role for the appearance of such novel structural features in <b>MOAAF 1</b>–<b>6</b> since they were found to act as bases responsible for the deprotonation of H₃btc, templates, and chelating ligands. Specifically, most of the compounds synthesized were shown to be templated by protonated amino-alcohols that are involved in hydrogen bonding interactions with the frameworks, whereas in two cases (compounds <b>MOAAF-5</b> and <b>MOAAF-6</b>) the amino-alcohols acted as chelating ligands affecting significantly the underline topology of the MOFs. The thermal stability and photoluminescence properties of the MOFs are also discussed. This work represents the initial systematic investigation on the use of combination of amino-alcohols and polycarboxylate ligands for the synthesis of new MOFs, demonstrating it as a powerful synthetic strategy for the isolation of novel MOFs

A Systematic Evaluation of the Interplay of Weak and Strong Supramolecular Interactions in a Series of Co(II) and Zn(II) Complexes Tuned by Ligand Modification

A systematic investigation on a designed series of 21 transition metal complexes has been carried out with the intention to explore and assess the relative strength and the way in which intermolecular interactions, namely, weak and strong hydrogen-bonding and π–π interactions, cooperate and direct molecular association during crystallization. The complexes were prepared using the general M^II/X^–/L or HL′ (M^II = Co^II, Zn^II; X^– = Cl^–, Br^–, I^–, NO₃^–, NO₂^–, ClO₄^–; L = 1-methyl-4,5-diphenylimidazole; and HL′ = 4,5-diphenylimidazole) reaction system and were characterized by single-crystal X-ray crystallography. Although the two ligands are structurally similar, the crystal packing organization of their complexes is markedly different. In structures with L, the 3D assembly is based only on weak C–H···X, C–H···π, and intramolecular π···π stacking interactions, whereas in those with HL′, it is the recurring N–H···X motifs that clearly dominate and guide the molecular self-assembly. The formation of such synthons has been activated by choosing appropriate anions X, acting as terminal ligands or counterions. In parallel, the conformational flexibility of the two ligands serves a dual purpose: (i) L contributes to the stabilization of complexes via intramolecular π···π stacking interactions, and (ii) HL′ facilitates the synthon formation by adopting appropriate conformations, even at the expenses of the stabilizing intramolecular π···π stacking