Ferdinando Costantino

Synthesis, breathing, and gas sorption study of the first isoreticular mixed-linker phosphonate based metal–organic frameworks

The synthesis of the first water stable isoreticular phosphonate based mixed-linker metal-organic frameworks (MOFs) is achieved via the use of the N-donor heterocyclic co-ligands. Furthermore, these isoreticular phosphonate frameworks show selective CO(2)/N(2) uptake at low pressures.

Survey on the phase transitions and their effect on the ion-exchange and on the proton-conduction properties of a flexible and robust Zr phosphonate coordination polymer.

The flexible zirconium tetraphosphonate coordination polymer with formula Zr(O(3)PCH(2))(2)N-C(6)H(10)-N(O(3)CH(2)P)(2)X(2-x)H(2+x)·nH(2)O (X = H, Li, Na, K, 0 < x < 1, 4 < n < 7.5) (1) possesses an open framework structure with 1D cavities decorated with polar and acids P═O and P-OH groups. 1 has been fully protonated by adding HCl and then subjected to several acid-base ion-exchange reactions with alkaline metals hydroxides. 1 is a very robust coordination polymer because it can be regenerated in H- form using strong acid solutions and ri-exchanged several times without hydrolysis and loss of crystallinity. The flexibility of 1 has been also studied by means of TDXD (temperature dependent X-ray diffraction) evidencing remarkable phase transformations that lead to a different disposition of the water molecules. These transformations also influence the accessibility of the cations on the P-OH groups placed inside the channels and thus the ion-exchange properties. The dependence of the proton conductivity properties on these phase transitions has been also investigated and discussed.

Water-mediated proton conduction in a robust triazolyl phosphonate metal-organic framework with hydrophilic nanochannels.

The development of water-mediated proton-conducting materials operating above 100 °C remains challenging because the extended structures of existing materials usually deteriorate at high temperatures. A new triazolyl phosphonate metal-organic framework (MOF) [La3L4(H2O)6]Cl⋅x H2O (1, L(2-) = 4-(4H-1,2,4-triazol-4-yl)phenyl phosphonate) with highly hydrophilic 1D channels was synthesized hydrothermally. Compound 1 is an example of a phosphonate MOF with large regular pores with 1.9 nm in diameter. It forms a water-stable, porous structure that can be reversibly hydrated and dehydrated. The proton-conducting properties of 1 were investigated by impedance spectroscopy. Magic-angle spinning (MAS) and pulse field gradient (PFG) NMR spectroscopies confirm the dynamic nature of the incorporated water molecules. The diffusivities, determined by PFG NMR and IR microscopy, were found to be close to that of liquid water. This porous framework accomplishes the challenges of water stability and proton conduction even at 110 °C. The conductivity in 1 is proposed to occur by the vehicle mechanism.

A Highly Enantioselective One‐Pot Synthesis of Spirolactones by an Organocatalyzed Michael Addition/Cyclization Sequence

Spirocyclic compounds are attractive targets in organic synthesis because of their broad distribution in biologically active natural products and pharmaceuticals, as well as their increasing use in a range of important chemical and technological processes, such as asymmetric synthesis and organic optoelectronics. On this basis the development of novel methods for the construction of spirocyclic frameworks is of considerable importance, particularly when these methods give rise to the enantioselective formation of an all-carbon quaternary stereocenter, which itself is considered to be a challenging transformation. 4] Over the past decade, extensive work on organocatalyzed asymmetric conjugated additions of trisubstituted carbon nucleophiles to electron-deficient alkenes demonstrated that these reactions represent an attractive solution to the problem of selectively generating quaternary stereocenters. Recently several organocatalytic cascade processes involving Michael additions have been successfully applied to the synthesis of spirocyclic compounds. These methods, are based on Michael or Michael/ aldol-type sequences and provide access to spiro-oxindoles, spirobenzofuranones, or spiro-3,4-dihydropyrans with high stereocontrol. The use of novel substrate combinations and the development of new cascade or one-pot reactions are significant advances in this field, thus making the asymmetric assembly of structurally diverse spirocyclic compounds possible from simple and readily available precursors. In this field and in continuation of our efforts to expand the scope of privileged organocatalysts in the field of selenium chemistry, 7] we herein report the first highly enantioselective synthesis of spirolactones starting from racemic cyclic bketoesters and the vinyl selenone catalyzed by bifunctional cinchona-alkaloid-derived catalysts. The operationally simple, one-pot Michael addition/cyclization sequence is based on the peculiar properties of the phenylselenonyl substituent, which plays a dual role as an electron-withdrawing group, during the addition step, and as a leaving group, during the cyclization by intramolecular nucleophilic substitution. Initial studies were performed with an excess of the tertbutyl b-ketoester 1a and the easily available vinyl selenone 2 in toluene in the presence of a catalytic amount of anhydrous Na2CO3 (Scheme 1).

New insights on the incorporation of lanthanide ions into nanosized layered double hydroxides.

Nanosized Layered Double Hydroxides (LDH) were prepared in confined environment through the microemulsion method in the presence of different lanthanide cations (Ln(III) = Eu(III), Yb(III), Tb(III), and Nd(III)). To investigate the effects of lanthanide insertion in the sheets of LDH materials, several samples were prepared upon progressively increasing the content of Ln ions and properly reducing the Al(III) amount; the samples were characterized in terms of metal content, structure, morphology, thermal behavior, and spectroscopic properties. The data revealed that Ln(III) content in the LDH samples depends on the ionic radius of the lanthanide cations and on its concentration in the starting microemulsion. X-ray powder diffraction (XRPD) indicated that Eu(III) can be inserted into the LDH structure in average atomic percentages lower than 2.7%, leading to the formation of a low symmetry phase, as confirmed by steady state luminescence spectra; while Yb(III) can be incorporated into the layer structure up to about 10% forming a pure layered phase containing the lanthanide in the sheet. The incorporation of Yb(III) and Eu(III) into the LDH sheets is also supported by FT-IR measurements. Coupled thermogravimetrical (TG) and differential scanning calorimetric (DSC) studies indicated that water molecules are essential in the coordination sphere of incorporated Ln cations; this observation accounts for the lower thermal stability of Ln-doped LDH compared to the undoped ones. Furthermore, Eu-luminescence measurements indicates that the lanthanide inclusion does not compromise its luminescence although the spectral position and brightness can be tuned by the loading.

A Layered Mixed Zirconium Phosphate/Phosphonate with Exposed Carboxylic and Phosphonic Groups: X-ray Powder Structure and Proton Conductivity Properties

A novel mixed zirconium phosphate/phosphonate based on glyphosine, of formula Zr2(PO4)H5(L)2·H2O [L = (O3PCH2)2NCH2COO], was synthesized in mild conditions. The compound has a layered structure that was solved ab initio from laboratory PXRD data. It crystallizes in the monoclinic C2/c space group with the following cell parameters: a = 29.925(3), b = 8.4225(5), c = 9.0985(4) Å, and β = 98.474(6)°. Phosphate groups are placed inside the sheets and connect the zirconium atoms in a tetradentate fashion, while uncoordinated carboxylate and P-OH phosphonate groups are exposed on the layer surface. Due to the presence of these acidic groups, the compound showed remarkable proton conductivity properties, which were studied in a wide range of temperature and relative humidity (RH). The conductivity is strongly dependent on RH and reaches 1 × 10(-3) S cm(-1) at 140 °C and 95% RH. At this RH, the activation energy of conduction is 0.15 eV in the temperature range 80-140 °C. The similarities of this structure with related structures already reported in the literature were also discussed.

Solvent dependent synthesis of micro- and nano- crystalline phosphinate based 1D tubular MOF: structure and CO2 adsorption selectivity

A novel porous tubular 1D-MOF, built from Cu(II), 1,2-bis(4-pyridyl)ethane and P,P′-diphenyl-diphosphinate, has been prepared by an easy and direct self-assembly process in either needle microcrystal or nanorod form depending on the synthesis conditions. The CO2 absorption kinetics drastically increased from the micrometric crystals to the nanorods. The selectivity towards other gases and polar solvents was also investigated.

Synthesis, Crystal Structure, and Proton Conductivity of One-Dimensional, Two-Dimensional, and Three-Dimensional Zirconium Phosphonates Based on Glyphosate and Glyphosine

The reaction of two small phosphono-amino acids based on glycine (glyphosine and glyphosate) with zirconium under mild conditions led to the attainment of three related zirconium derivatives with 1D, 2D, and 3D structures of formulas ZrF[H3(O3PCH2NHCH2COO)2] (1), Zr3H8[(O3PCH2)2NCH2COO]4·2H2O (2), and Zr[(O3PCH2)(HO3PCH2)NHCH2COOH]2·2H2O (3), respectively, whose structures were solved by X-ray powder and single-crystal diffraction data. The glyphosate derivative has 1D ribbon-type structure whereas the dimensionality of the glyphosine-derived materials (2D and 3D) can be tuned by changing the synthesis conditions. The low-dimensional compounds (1 and 2) can be directly produced in the form of nanoparticles with different size and morphology whereas the 3D compound (3) has a higher crystallinity and can be obtained as single crystals with a prismatic shape. The different structural dimensionality reflects the shape and size of the crystals and also differently affects the proton conductivity properties, measured over a wide range of temperature at 95% relative humidity. Their high thermal and chemical stability together with the small size may promote their use as fillers for polymeric electrolyte membranes for fuel cells applications.

Studies the effects of ultrasonic irradiation and dielectric constants of solvents on formation of lead(II) supramolecular polymer; new precursors for synthesis of lead(II) oxide nanoparticles

In order to evaluation the effects of ultrasonic irradiations and dielectric constants of solvents on formation [Pb2(5-Clq-8-ol)2(OAc)2]n (1), [H5-Clq-8-ol=5-chloroquinolin-8-ol and OAc-=acetate], we designed some experiments and synthesized six samples of 1 under different conditions. Microrods of a lead(II) supramolecular polymer, were synthesized under these conditions. These microstructures were characterized by IR spectroscopy, X-ray powder diffraction (XRD) and Scanning Electron Microscopy (SEM). The results indicated that compound 1 with the best crystallinity can be obtained in the presence of MeCN and H2O (as the bulk sample) and in the presence of MeCN and EtOH (by sonochemical process). The least agglomeration of microrods was observed in H2O which is due to high dielectric constant of it. By considering all of the factors consist of crystallinity and agglomeration of the products and their corresponding histograms, it seems that MeCN is the best solvent for synthesis of 1. The samples which were synthesized in the presence of MeCN, had been used as new precursors for fabricating lead(II) oxide nanoparticles via thermal decomposition in oleic acid (OA).

Nanosized zirconium phosphate/AgCl composite materials: a new synergy for efficient photocatalytic degradation of organic dye pollutants

A new class of AgCl-based composite photocatalysts has been quickly and easily obtained by using nanosized silver(I) exchanged α-zirconium phosphate as a precipitating agent. Different ZP/xAgCl composite catalysts, having AgCl/ZP molar ratio (x) = 0.28, 0.56, and 1.16, were prepared and characterized by X-ray diffraction analysis, scanning electron microscopy/energy dispersive X-ray spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The photocatalytic properties of the ZP/xAgCl composites, having particle size ≤1 μm, were investigated in the degradation of Rhodamine B, and compared with those of an AgCl sample, with particle size ranging from 0.5 to 2 μm. The ZP/1.16AgCl turned out to be the best photocatalyst, providing a complete chromophore structure cleavage in 15 minutes; differently, in the presence of the pure AgCl sample, the concentration of the chromophore species after 30 minutes was about half of the initial one. Moreover, the catalytic activity of ZP/1.16AgCl was evaluated for three consecutive catalytic tests, and an almost complete chromophore structure cleavage was achieved in 10 minutes during the third run.