Begoña Bazán

Ionothermal synthesis is a little used method for the preparation of coordination polymers. By this method, two cadmium compounds were synthesized, 1, with formula Cd₃(ox)F₂(Ina)₂ (Ina = isonicotinate) and 2, Cd(NO₃)₂(4,4′-Bpy) (4,4′-Bpy = 4,4′-Bipyridine). The modification of the reaction conditions has allowed to obtain 2 as a pure phase. The structure of both compounds was determined by a single-crystal X-ray diffraction. Compound 1 is isostructural to the previously reported Cd₂Zn(ox)(OH)₂(Ina)₂. It crystallizes in the monoclinic space group P2₁/n and present a three-dimensional (3D) network, built-up from [Cd₃(ox)F₂]_n²ⁿ⁺ layers, linked by isonicotinate ligands. Crystals of 2 are formed by twins of two components which are rotated ca. 180° to each other. This compound crystallizes in the triclinic P-1 space group and its structure can be describe as a two-dimensional (2D) 4 connected ‘sql’ net. The layers are composed by [Cd(NO₃)₂]_n chains linked through 4,4′-Bpy ligands, and are pillared along the [011] direction. The thermal decomposition of 2 was studied by thermogravimetric and thermodiffractiometric techniques. The compound decomposes gradually starting from 160 °C, and due to heating, the structure suffers slight reversible changes in the bond distances and angles.

Heterogeneous catalysts are of great interest in many industrial processes for environmental reasons and, during recent years, a great effort has been devoted to obtain metal–organic frameworks (MOFs) with improved catalytic behaviour. Few supramolecular metal–organic frameworks (SMOFs) are stable under ambient conditions and those with anchored catalysts exhibit favourable properties. However, this paper presents an innovative approach that consists of using metal nodes as both structural synthons and catalysts. Regarding the latter, metalloporphyrins are suitable candidates to play both roles simultaneously. In fact, there are a number of papers that report coordination compounds based on metalloporphyrins exhibiting these features. Thus, the aim of this bioinspired work was to obtain stable SMOFs (at room temperature) based on metalloporphyrins and explore their catalytic activity. This work reports the environmentally friendly microwave-assisted synthesis and characterization of the compound [H(bipy)]₂[(MnTPPS)(H₂O)₂]·2bipy·14H₂O (TPPS = meso-tetraphenylporphine-4,4′,4′′,4′′′-tetrasulfonic acid and bipy = 4,4′-bipyridine). This compound is the first example of an MnTPPS-based SMOF, as far as we are aware, and has been structurally and thermally characterized through single-crystal X-ray diffraction, IR spectroscopy, thermogravimetry and transmission electron microscopy. Additionally, this work explores not only the catalytic activity of this compound but also of the compounds μ-O-[FeTCPP]₂·16DMF and [CoTPPS_0.5(bipy)(H₂O)₂]·6H₂O. The structural features of these supramolecular materials, with accessible networks and high thermal stability, are responsible for their excellent behaviour as heterogeneous catalysts for different oxidation, condensation (aldol and Knoevenagel) and one-pot cascade reactions.

Heterogeneous catalysts are greatly preferred for green chemistry in many industrial processes and, in the past decade, promising results have been achieved in order to improve the catalytic activity of metal organic frameworks (MOFs). Accordingly, porphyrins make the design of new coordination polymers with better properties possible, taking into account the important functions they develop in nature. In this sense, porphyrin-based MOFs are becoming very relevant in heterogeneous catalysis. Thus, the aim of this work was to obtain metalloporphyrinic MOFs exhibiting catalytic activity. Studying the effect of dimensionality on the MOF properties (including thermal stability and catalytic activity), in this work, we study two catalysts with different dimensionalities, 3D [Ni₅(H₂TCPP)₂O(H₂O)₄]·nS (1) and 0D [Cu(H₄TCPP)]·6DMF (2) (where H₆TCPP is meso-tetra(4-carboxyphenyl)porphyrin, DMF is N,N-dimethylformamide and S is the solvent). The structural features of both compounds, combined with their high thermal stability and accessible networks, are responsible for their excellent behaviour as heterogeneous catalysts. It is worth mentioning that a significant reduction in reaction time compared to other reported catalysts has been observed. The recyclability of one of the herein studied porphyrin-based MOFs is outstanding. Further structural and thermal characterization has been carried out by means of single crystal X-ray diffraction, IR spectroscopy, thermogravimetry (TG), powder X-ray diffraction (XRD) and transmission electron microscopy (TEM).

In this paper, we have completed the synthesis and characterization of a family of aluminum alkali metalate derivatives [MAlMe_4–x{2,6‐(MeO)₂C₆H₃O}_x]_n (x = 1, 2; M = Li, Na, K) by preparing the new heterometallic ‐ate compounds [MAlMe₃{2,6‐(MeO)₂C₆H₃O}]₂ (M = Na and K) through the reaction between [AlMe₃]₂ and the appropriate alkali metal aryloxide [M{2,6‐(MeO)₂C₆H₃O}]_n (M = Na and K). Surprisingly, the solid‐state structures for these species, determined by X‐ray diffraction, show a different nuclearity than the lithium one, [AlLiMe₃{2,6‐(MeO)₂C₆H₃O}]₃ previously reported by us. This behavior contrasts to the one observed when [Al(OR)Me₂] is used as the aluminum precursor, which gives the tetrametallic species [AlMMe₂{2,6‐(MeO)₂C₆H₃O}₂]₂. To rationalize the origins of the final nuclearity variation in the solid state within this family of heterometallic ‐ate compounds, a DFT study has been performed. The results of this analysis on whether the nuclearity in the solid state could stem from crystallization factors or from how the chemical attack had taken place are presented.

Metal organic frameworks (MOFs) are crystalline materials based on connections between metal ions through organic ligands. The combination of polycarboxylate anions and dipyridyl ligands is an effective strategy for producing extended structures. In this sense, the combination of bpa with m‐bdc [bpa = 1,2‐bis(4‐pyridyl)ethane, m‐bdc = 1,3‐benzenedicarboxylate] has produced three new Cu^II‐based networks with different dimensionalities, namely the 1D [Cu(m‐bdc)(bpa)_0.5(H₂O)dmf]·0.5H₂O (1, synthesis based on sonication and slow evaporation), the 2D [Cu₆(m‐bdc)₆(bpa)₆(dmf)₃]·8dmf (2, microwave synthesis) and the 3D [Cu₄(m‐bdc)₄(bpa)₂dmf]·dmf (3, microwave synthesis). The three compounds have been structurally characterized by means of single‐crystal X‐ray diffraction, IR and UV/Vis spectroscopy and elemental analysis. An unprecedented Cu^II dimer has been observed for compound 3. The thermal behaviour of the compounds was analysed by thermogravimetry (TG/DSC) and X‐ray thermodifractometry (TDX), and it was concluded that the dimensionality plays an important role in their thermal properties. Electronic paramagnetic resonance and magnetic susceptibility measurements for compounds 1 and 3 showed that antiferromagnetic interactions exist between the metal ions.

Cu^II nanoballs have been determined to be among the best MOPs (Metal–Organic Polyhedra) reported so far for the adsorption of small molecules, with the highlighting advantage of rapid kinetics, which focuses on their applicability to the removal of emerging pollutants.

Water-induced reversible phase transformation in the Cu^II–PDC–(py)₂C(OH)₂ system.