Sabina Rodríguez-Hermida

Spray Drying for Making Covalent Chemistry: Postsynthetic Modification of Metal–Organic Frameworks

Covalent postsynthetic modification (PSM) of metal-organic frameworks (MOFs) has attracted much attention due to the possibility of tailoring the properties of these porous materials. Schiff-base condensation between an amine and an aldehyde is one of the most common reactions in the PSM of MOFs. Here, we report the use of the spray drying technique to perform this class of organic reactions, either between discrete organic molecules or on the pore surfaces of MOFs, in a very fast (1-2 s) and continuous way. Using spray drying, we show the PSM of two MOFs, the amine-terminated UiO-66-NH2 and the aldehyde-terminated ZIF-90, achieving conversion efficiencies up to 20 and 42%, respectively. Moreover, we demonstrate that it can also be used to postsynthetically cross-link the aldehyde groups of ZIF-90 using a diamine molecule with a conversion efficiency of 70%.

Control over the preparation of two pH-dependent Cu(II) supramolecular isomers based on 1,3,5-benzenetricarboxylic acid and the bis(4-pyridylthio)methane ligand

The possibility of controlling the formation of copper(II) coordination polymers based on the rigid carboxylate ligand 1,3,5-benzenetricarboxylic acid (H3btc) and an N,N-divergent spacer with conformational flexibility, bis(4-pyridylthio)methane (SCS), was investigated. The new coordination polymers 1∞[Cu(H2btc)2(SCS)] (1) and 2∞[Cu(Hbtc)(SCS)2]·H2O (2) have been prepared and characterized. Compounds 1 and 2 were obtained as a mixture and optimization of the synthetic conditions allowed the isolation of pure phases in high yield. Topological analysis showed the interpenetration of three networks with a vcm-type topology in 2. The thermal stability and the structural dynamics of these systems have also been investigated.

Homo‐ and Heteronuclear Compounds with a Symmetrical Bis‐hydrazone Ligand: Synthesis, Structural Studies, and Luminescent Properties

Nine new coordination compounds have been synthesized by the reaction of salts of bivalent metal ions (a=Zn(II) , b=Cu(II) , c=Ni(II) , d=Co(II) ) with the bis(benzoylhydrazone) derivative of 4,6-diacetylresorcinol (H4 L). Three kinds of complexes have been obtained: homodinuclear compounds [M2 (H2 L)2 ]⋅nH2 O (1 a, 1 b, 1 c, and 1 d), homotetranuclear compounds [M4 (L)2 ]⋅n(solv) (2 a and 2 c), and heterotetranuclear compounds [Zn2 M2 (L)2 ]⋅n(solv) (2 ab, 2 ac, and 2 ad). The structures of the free ligand H4 L⋅2 DMSO and its complexes [Zn2 (H2 L)2 (DMSO)2 ] (1 a*), [Zn4 (L)2 (DMSO)6 ] (2 a*), and [Zn0.45 Cu3.55 (L)2 (DMSO)6 ]⋅2 DMSO (2 ab*) were elucidated by single-crystal X-ray diffraction. The ligand shows luminescence properties and its fluorimetric behavior towards M(II) metals (M=Zn, Cu, Ni and Co) has been studied. Furthermore, the solid-state luminescence properties of the ligand and compounds have been determined at room temperature. (1) H NMR spectroscopic monitoring of the reaction of H4 L with Zn(II) showed the deprotonation sequence of the OH/NH groups upon metal coordination. Heteronuclear reactions have also been monitored by using ESI-MS and spectrofluorimetric techniques.

A Hexameric Cationic Copper(II) Metallacrown as a Pertechnetate and Perrhenate Scavenger

Materials based on the cationic copper(II) hexanuclear 18-membered metallacrown [18-MCCuII-N(2ph)-6](6+) (2phH=2-piconyl hydrazide) and tetrafluoroborate, perchlorate, nitrate, sulfate, and perrhenate anions were prepared by an easy method in aqueous medium. Single-crystal X-ray characterization of six members of this new family of complexes showed that the anions are attached to the metallacrown by direct coordination to a copper cation or by hydrogen-bonding interaction with the center of the hexamer. The stable cationic nature of the complexes and their ability to bind different anions allows them to adsorb and immobilize environmentally relevant anions such as MO4(-) (M=Tc, Re). The MO4(-) trapping capacities suggest that these materials would be useful in the treatment of oxoanionic contaminants in water.

Boosting Self-Assembly Diversity in the Solid-State by Chiral/Non-Chiral ZnII-Porphyrin Crystallization

A chiral ZnII porphyrin derivative 1 and its achiral analogue 2 were studied in the solid state. Considering the rich molecular recognition of designed metalloporphyrins 1 and 2 and their tendency to crystallize, they were recrystallized from two solvent mixtures (CH2 Cl2 /CH3 OH and CH2 Cl2 /hexane). As a result, four different crystalline arrangements (1 a,b and 2 a,b, from 0D to 2D) were obtained. Solid-state studies were performed on all the species to analyze the role played by chirality, solvent mixtures, and surfaces (mica and HOPG) in the supramolecular arrangements. By means of combinations of solvents and substrates a variety of microsized species was obtained, from vesicles to flower-shaped arrays, including geometrical microcrystals. Overall, the results emphasize the environmental susceptibility of metalloporphyrins and how this feature must be taken into account in their design.