Solvent dependent nuclearity of manganese complexes with a polydentate hydrazone-based ligand and thiocyanate anions

The reaction of Mn(II) chloride with the 2-benzoylpyridyl-(2-picolyl)-hydrazone ligand (HL) and thiocyanate anions in different solvent systems affords mono- [Mn(HL)2(SCN)2] (1), di- [Mn2(HL)2(SCN)4] (2) and a tetra-nuclear complex [Mn4(L)4(SCN)4].2(CH3CN) (3) with concomitant different coordination modes of the ligands. Remarkably, the nuclearity of the complexes only depends on the solvent used, ethanol for 1, n-propanol for 2 and acetonitrile for 3. The complexes have been characterized by elemental analysis, IR spectroscopy technique and the molecular structures determined by single crystal X-ray analysis. In 1 and 2 the ligands are present in its neutral form, while they are deprotonated in 3, but more significantly in all structures a different denticity of ligands was detected: in complex 1 one molecule is tridentate coordinated though the N,N,O donor set, the other bidentate through N,O; in 2 the ligands is of N,N,O-tridentate; finally in 3 each ligand, acting as N,N,O,N-tetradentate species, bridges two metals to form a tetranuclear assembly. The crystal structures have been described using the Hirshfeld surface analysis. Finally, we have studied the ability of the thiocynato ligand to participate in H-bonding and C\u2013H/\u3c0 interactions by means of DFT calculations (B3LYP/6-31+G 17 17)

Metal-organic and supramolecular lead(II) networks assembled from isomeric nicotinoylhydrazone blocks : the effects of ligand geometry and counter-ion on topology and supramolecular assembly

A new series of six structurally diverse lead(II) coordination compounds was assembled from two isomeric nicotinoylhydrazones as neutral ligands and three Pb(II) salts with different monoanions (chloride, nitrate and thiocyanate) as starting materials. The products were isolated in good yields and were fully characterized, including by single-crystal Xray diffraction and theoretical methods. Within the six compounds, three feature 2D metal-organic networks, two are 1D coordination polymers, and another one comprises discrete 0D dimeric units. The structures of the latter low dimensional compounds are extendable into 2D supramolecular networks. The topology of the coordination or supramolecular networks is primarily dictated by the geometry of the nicotinoylhydrazone used as a main building block. In contrast, supramolecular interactions are greatly influenced by the choice of the anion in the starting lead(II) salt, which is demonstrated by Hirshfeld surface analysis. In fact, the topological analysis and classification of metal-organic or supramolecular underlying networks in the obtained compounds was performed, disclosing the hcb, 2C1, gek1, SP 1-periodic net (4,4)(0,2) and 3,4L83 topological types; the latter topology was docummented for three compounds, including both coordination and supramolecular networks. In two compounds containing thiocyanate moieties there are supramolecular contacts between thiocyanate anions and lead centres. These were shown by DFT calculations to be strong tetrel bonds (–15.3 and –16.7 kcal/mol) between the σ-hole of the lead atom and the π-system of the thiocyanate S–C bond

Tuning Proton Conductivity in A Multifunctional Calcium Phosphonate Hybrid Framework

Multi-chelating phosphonate ligands are organic linkers alternative to polycarboxylates and other ligands providing synthetic access to a number of thermally- and chemically-stable MOFs [1]. Metal phosphonates are amenable for accessing suitable and highly conducting materials both by tuning structural features and post-synthesis treatment [2,3]. For instance, proton conductivity values in the order of 10−2 S cm–1 have been reported for several phosphonate-based compounds [4]. We report hereby the synthesis, structural characterization and proton conductivity of an open framework hybrid, Ca2[(HO3PC6H3COOH)2]2[(HO3PC6H3(COO)2H).(H2O)2].5H2O, that combines Ca2+ ions and the rigid polyfunctional ligand 5-(dihydroxyphosphoryl)isophthalic acid. This compound was obtained by slow crystallization at ambient conditions at pH 3. Its complex pillared layered structure, solved by single crystal X-ray analysis, contains hydrophilic 1D channels filled with both water and acidic phosphonate and carboxylate groups creating a hydrogen-bonded network. Partial removal of the lattice water at 75 °C causes a monoclinic structural distortion but still retaining the initial conductivity properties (5.7x10-4 Sxcm-1). Exposure of the sample to ammonia vapor from a concentrated aqueous solution led to major structural changes resulting in a new layered material containing seven NH3 and sixteen H2O molecules per formula. This solid exhibits enhanced conductivity, reaching 6.6x10-3 S.cm-1, as measured at 98 % RH and T = 24 °C. Activation energies were between 0.23 and 0.40 eV, typical of a Grothuss mechanism of proton conduction.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyecto Excelencia Junta de Andalucía, FQM-1656. MAT2010-15175

Guest Molecule-Responsive Functional Calcium Phosphonate Frameworks for Tuned Proton Conductivity

We report the synthesis, structural characterization, and functionality of an open-framework hybrid that combines Ca2+ ions and the rigid polyfunctional ligand 5-(dihydroxyphosphoryl) isophthalic acid (PiPhtA). Ca-PiPhtA-I is obtained by slow crystallization at ambient conditions from acidic (pH≈3) aqueous solutions. It possesses a high water content (both Ca coordinated and in the lattice), and importantly, it exhibits water-filled 1D channels. At 75 °C, Ca-PiPhtA-I is partially dehydrated and exhibits a crystalline diffraction pattern that can be indexed in a monoclinic cell with parameters close to the pristine phase. Rietveld refinement was carried out for the sample heated at 75 °C, Ca-PiPhtA-II, using synchrotron powder X-ray diffraction data.All connectivity modes of the “parent” Ca-PiPhtA-I framework are retained in Ca-PiPhtA-II. Upon Ca-PiPhtA-I exposure to ammonia vapors (28% aqueous NH3) a new derivative is obtained (Ca-PiPhtA-NH3) containing 7 NH3 and 16 H2O molecules according to elemental and thermal analyses. Ca-PiPhtA-NH3 exhibits a complex X-ray diffraction pattern with peaks at 15.3 and 13.0 Å that suggest partial breaking and transformation of the parent pillared structure. Although detailed structural identification of Ca-PiPhtA-NH3 was not possible, due in part to nonequilibrium adsorption conditions and the lack of crystallinity, FT-IR spectra and DTA-TG analysis indicate profound structural changes compared to the pristine Ca-PiPhtA-I. At 98% RH and T = 24 °C, proton conductivity, σ, for Ca PiPhtA-I is 5.7 ×10−4 S·cm−1. It increases to 1.3 × 10−3 S·cm−1 upon activation by preheating the sample at 40 °C for 2 h followed by water equilibration at room temperature under controlled conditions. Ca-PiPhtA-NH3 exhibits the highest proton conductivity, 6.6 × 10−3 S·cm−1, measured at 98% RH and T = 24 °C. Ea for proton transfer in the above-mentioned frameworks range between 0.23 and 0.4 eV, typical of a Grothuss mechanism of proton conduction.Proyecto nacional MAT2010-1517

Halide ion-driven self-assembly of Zn(ii) compounds derived from an asymmetrical hydrazone building block : a combined experimental and theoretical study

Three Zn(n) complexes, namely mononuclear derivatives [Zn(H2L)(2)I-2]center dot 2CH(3)OH (1) and [Zn(H2L)(2)Br-2]center dot 2CH(3)OH (2) and a tetranuclear cyclic compound [Zn-4(H2L)(4)Cl-8]center dot 4CH(3)OH (3) {H2L = p-hydroxybenzaldehyde isonicotinoylhydrazone}, were synthesized using a self-assembly method and fully characterized. Characterization included theoretical methods and single crystal X-ray diffraction. The molecular structures of compounds 1-3 demonstrate the effect of halide ions and the binding mode of H2L on self-assembly. The arrangement of the packing patterns in 1-3 is well explained by various types of non-covalent interactions. Notably, several types of strong H-bonding, C-H center dot center dot center dot O, and pi center dot center dot center dot pi interactions were also observed, which assist in the formation of 3D supramolecular networks. In the isostructural compounds 1 and 2, a tripod type H-bonding interaction of H2L with the methanol molecules of crystallization was observed. Furthermore, the terminal halide ligands exert H-bonding interactions with the -OH/-NH and -CH moieties of H2L. In all compounds, the supramolecular 3D networks, driven by strong H-bonding interactions, were simplified by topologial analysis. This showed a 6-connected framework with a unique topology in 1 and 2, and an 8-connected framework with bcu topology in 3 (the latter is composed of cyclic tetrazinc(II) cluster units with 2M4-1 topology). In addition, the discussion on coordination geometries and non-covalent interactions was also supported using Hirshfeld surface analysis and DFT calculations

Combining Three Different Functional Groups in One Linker: A Variety of Features of Copper(II) Aminocarboxyphosphonate

While metal–organic frameworks (MOFs) or, more generally, coordination polymers (CPs) built using linkers possessing two different functional groups are known very well in the literature, the effect of a third functional group on the physico­chemical properties of those materials is weakly recognized. To study this issue we designed an amino­carboxy­phosphonic ligand, 3-amino-5-(dihydroxy­phosphoryl)­benzoic acid (<b>H</b>_<b>3</b><b>APB</b>), which is an amino derivative of <i>meta</i>-phosphono­benzoic acid. By self-assembly with a copper­(II) source, we obtained the three-dimensional CP {[Cu₃­(APB)₂­(H₂O)₆]·​6H₂O}_<i>n</i>, <b>1</b>, featuring rare binodal 4,5-connected <b>tcs</b> topology. By comparison with previously known representatives of that topology, we put forward a hypothesis that CPs of rare topologies, such as <b>tcs</b>, are obtained when polytopic, differentially substituted ligands are used. The structure of <b>1</b> is layered, but not in the manner typical for “traditional” metal phosphonates and carboxy­phosphonates, and it was found to be flexible; structural flexibility has been demonstrated by dehydration–hydration experiments. The structural changes were probed with the use of PXRD and IR methods. We have also shown that the copper­(II) amino­carboxy­phosphonate <b>1</b> presented herein has moderate capability for degradation of methylene blue, rhodamine B, and acridine orange in oxidizing conditions; however, the rate of dye degradation is greatly enhanced under visible light irradiation. Analysis of magnetic properties revealed that <b>1</b> is a spin-frustrated system with a diamond-chain arrangement of copper­(II) ions. The magnetic data were fitted using the isotropic Heisenberg as well as Ising models. Both models consistently indicate that magnetic exchange paths are both antiferromagnetic and ferromagnetic, with dominating participation of the former interaction

Guest Molecule-Responsive Functional Calcium Phosphonate Frameworks for Tuned Proton Conductivity

We report the synthesis, structural characterization, and functionality (framework interconversions together with proton conductivity) of an open-framework hybrid that combines Ca²⁺ ions and the rigid polyfunctional ligand 5-(dihydroxyphosphoryl)­isophthalic acid (<b>PiPhtA</b>). Ca₂[(HO₃PC₆H₃COOH)₂]₂[(HO₃PC₆H₃(COO)₂H)­(H₂O)₂]·5H₂O (<b>Ca-PiPhtA-I</b>) is obtained by slow crystallization at ambient conditions from acidic (pH ≈ 3) aqueous solutions. It possesses a high water content (both Ca coordinated and in the lattice), and importantly, it exhibits water-filled 1D channels. At 75 °C, <b>Ca-PiPhtA-I</b> is partially dehydrated and exhibits a crystalline diffraction pattern that can be indexed in a monoclinic cell with parameters close to the pristine phase. Rietveld refinement was carried out for the sample heated at 75 °C, <b>Ca-PiPhtA-II</b>, using synchrotron powder X-ray diffraction data, which revealed the molecular formula Ca₂[(HO₃PC₆H₃COOH)₂]₂[(HO₃PC₆H₃(COO)₂H)­(H₂O)₂]. All connectivity modes of the “parent” <b>Ca-PiPhtA-I</b> framework are retained in <b>Ca-PiPhtA-II</b>. Upon <b>Ca-PiPhtA-I</b> exposure to ammonia vapors (28% aqueous NH₃) a new derivative is obtained (<b>Ca-PiPhtA-NH</b>_<b>3</b>) containing 7 NH₃ and 16 H₂O molecules according to elemental and thermal analyses. <b>Ca-PiPhtA-NH</b>_<b>3</b> exhibits a complex X-ray diffraction pattern with peaks at 15.3 and 13.0 Å that suggest partial breaking and transformation of the parent pillared structure. Although detailed structural identification of <b>Ca-PiPhtA-NH</b>_<b>3</b> was not possible, due in part to nonequilibrium adsorption conditions and the lack of crystallinity, FT-IR spectra and DTA-TG analysis indicate profound structural changes compared to the pristine <b>Ca-PiPhtA-I</b>. At 98% RH and <i>T</i> = 24 °C, proton conductivity, σ, for <b>Ca-PiPhtA-I</b> is 5.7 × 10^–4 S·cm^–1. It increases to 1.3 × 10^–3 S·cm^–1 upon activation by preheating the sample at 40 °C for 2 h followed by water equilibration at room temperature under controlled conditions. <b>Ca-PiPhtA-NH</b>_<b>3</b> exhibits the highest proton conductivity, 6.6 × 10^–3 S·cm^–1, measured at 98% RH and <i>T</i> = 24 °C. Activation energies (<i>E</i>_a) for proton transfer in the above-mentioned frameworks range between 0.23 and 0.4 eV, typical of a Grothuss mechanism of proton conduction. These results underline the importance of internal H-bonding networks that, in turn, determine conductivity properties of hybrid materials. It is highlighted that new proton transfer pathways may be created by means of cavity “derivatization” with selected guest molecules resulting in improved proton conductivity