Andrea Ienco

Hyperquad simulation and speciation (hyss): a utility program for the investigation of equilibria involving soluble and partially soluble species

Abstract Hyperquad simulation and speciation (HySS) is a computer program written for the Windows operating system on personal computers which provides (a) a system for simulating titration curves and (b) a system for providing speciation diagrams. The calculations relate to equilibria in solution and also include the possibility of formation of a partially soluble precipitate. There are no restrictions as to the number of reagents that may be present or the number of complexes that may be formed.

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.

Synthesis, antiapoptotic biological activity and structure of an oxo-vanadium(IV) complex with an OOO ligand donor set

Abstract The oxo–vanadium(IV) complex VO(oda)(H2O)2 (1) (oda=oxydiacetate, O(CH2COO−)2) was obtained by reaction of aerobic aqueous solutions of VO(acac)2 with oxydiacetic acid, O(CH2COOH)2. The antiapoptotic biological activity of 1 was studied in insulin-producing cells. Chemically generated nitric oxide (NO) triggers apoptotic events, such as the appearance of oligonucleosomes in cytosol, and this response was prevented by the presence of 1 in the culture medium. The molecular structure of 1 has been determined by X-ray diffraction analysis.

Synthesis and molecular structure of oxydiacetate complexes of nickel(II) and cobalt(II). Theoretical analysis of the planar and non-planar conformations of oxydiacetate ligand and oxydiacetic acid

A novel synthetic route to [Ni(oda)(H2O)3]·1.5H2O 1 and [Co(oda)(H2O)2]·H2O 2 [oda = oxydiacetate, O(CH2CO2−)2] is presented. These complexes react with bidentate N-donor ligands to yield compounds of general formula [M(oda)(N–N)(H2O)] (M = Ni, N–N = bipy, 3; phen, 5; tmeda, 7. M = Co, N–N = bipy, 4; phen, 6; tmeda, 8), which can be isolated as crystalline solids with different numbers of hydration water molecules. The molecular structures of the compounds 3 and 4 have been shown by X-ray analysis to crystallize with 2.5H2O. In these compounds, the oda ligand adopts a planar, tridentate conformation (mer) in binding the octahedral metal centre. By contrast, the recent X-ray characterization of 1 has shown that the oxydiacetate ligand completes the octahedral coordination of the metal in the fac arrangement. The DFT method has been adopted to investigate theoretically the flexibility of this ligand. First, calculations have been carried out on the free oxydiacetic acid (H2oda) and its anion. Then, a model of 1 has been studied in order to find the geometric and energetic implications for the alternative oda conformations (mer and fac) in reaching the octahedral environment about the metal. In general, the geometric parameters are in good agreement with those available from crystal structures. From the energetic viewpoint, the mer conformation is favoured by a small energy difference (2.0 kcal mol−1). On the other hand, the fac conformation in 1 may be justified with the presence of the water hydration molecules (not considered by our model) which may deeply affect the energetics of the overall system by forming strong hydrogen bonds with the oxydiacetate ligand.

Structure and vibrational spectroscopy of methanesulfonic acid hydrazide: an experimental and theoretical study

A comprehensive study of the molecule of methanesulfonic acid hydrazide (MSH) is presented. The X-ray structure shows that in the crystal two centrosymmetrically oriented MSH molecules are held together by N–H···N hydrogen bonding interactions. This feature is unprecedented for the known arylsulfonic hydrazide analogues. The energetics of the various MSH staggered conformers and the stabilisation due to dimerisation are evaluated by HF abinitio calculations. Moreover, the pathways that interconvert the conformers as well as their enantiomers are outlined. The transition states between conformers correspond to the eclipsed conformation about the S–N linkage while those between enantiomers require planarisation of the N atom bound to sulfur. Some interconversions require two steps and two barriers to be bypassed. The IR and Raman spectra of MSH have been recorded and a normal coordinate analysis (NCA) has been carried out. The assignments have been double-checked through the abinitio calculated frequencies. The latter techniques also allow evaluation of the normal modes of vibration due to interacting MSH monomers, which can be experimentally detected.

Chiral Diaminopyrrolic Receptors for Selective Recognition of Mannosides, Part 2: A 3D View of the Recognition Modes by X‐ray, NMR Spectroscopy, and Molecular Modeling

The structural features of a representative set of five complexes of octyl α- and β-mannosides with some members of a new generation of chiral tripodal diaminopyrrolic receptors, namely, (R)-5 and (S)- and (R)-7, have been investigated in solution and in the solid state by a combined X-ray, NMR spectroscopy, and molecular modeling approach. In the solid state, the binding arms of the free receptors 7 delimit a cleft in which two solvent molecules are hydrogen bonded to the pyrrolic groups and to the benzenic scaffold. In a polar solvent (CD(3)CN), chemical shift and intermolecular NOE data, assisted by molecular modeling calculations, ascertained the binding modes of the interaction between the receptor and the glycoside for these complexes. Although a single binding mode was found to adequately describe the complex of the acyclic receptor 5 with the α-mannoside, for the complexes of the cyclic receptors 7 two different binding modes were required to simultaneously fit all the experimental data. In all cases, extensive binding through hydrogen bonding and CH-π interactions is responsible for the affinities measured in the same solvent. Furthermore, the binding modes closely account for the recognition preferences observed toward the anomeric glycosides and for the peculiar enantiodiscrimination properties exhibited by the chiral receptors.

Modulation of properties in analogues of Zeise's anion on changing the ligand trans to ethene. X-Ray crystal structures of trans-[PtCl2(OH)(η2-C2H4)]− and trans-[PtCl2(η1-CH2NO2)(η2-C2H4)]−

To get further insight in the reaction of nucleophilic substitution upon changing the ligand trans to a η(2)-olefin, the reactivity of some monoanionic platinum(II) complexes (trans-[PtCl(2)X(η(2)-C(2)H(4))](-), X = Cl(-), 1, OH(-), 2, and CH(2)NO(2)(-), 3) towards pyridines with different steric hindrance (py, 4-Mepy, and 2,6-Me(2)py) has been tested. All crystallographic (2 and 3 reported for the first time) and spectroscopic data are in accord with a platinum-olefin interaction decreasing in the order 2 > 1 > 3, paralleling the decreasing electronegativity of the donor atom (O > Cl > C). Not only the platinum-olefin bond but also the bond between platinum and the ligand trans to the olefin appear to be strongest in 2 (Pt-O distance at the lower limit for this type of bond). In the reaction with py, the ligand trans to the olefin is displaced in 1 and 2. Moreover the reaction is in equilibrium in the case of sterically hindered 2,6-Me(2)py, the equilibrium being shifted moderately or prevalently toward the reagents in the case of 1 and 2, respectively. In the case of 3, the reaction with pyridines leads to substitution of the olefin instead of the carbanion. This is in accord with the observation that carbanions strongly weaken the trans Pt-olefin bond.

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.

Intramolecular d10-d10 interactions in a Ni6C(CO)9(AuPPh3)4 bimetallic nickel-gold carbide carbonyl cluster.

The Ni6C(CO)9(AuPPh3)4 bimetallic carbide carbonyl cluster was obtained from the reaction of [Ni9C(CO)17](2-) with Au(PPh3)Cl. It contains a rare carbon-centered (distorted) Ni6C octahedral core decorated by four Au(PPh3) fragments. These are μ3-bonded to four contiguous Ni3-triangular faces and display weak intramolecular Au···Au d(10)-d(10) interactions. The cluster has been characterized in the solid state on two different solvato crystals, i.e., Ni6C(CO)9(AuPPh3)4·THF and Ni6C(CO)9(AuPPh3)4·THF·0.5C6H14. The two solvates show some interesting differences concerning the weak Au···Au contacts. Density functional theory calculations have demonstrated that the presence of the two isomers is related to solid-state packing effects and not to the existence of two double minima in the potential energy surface. This, in turn, confirms that Au···Au d(10)-d(10) interactions are rather soft and thus influenced also by weak van der Waals forces because of the interaction of the cluster with the cocrystallized solvent molecules.

Water-Soluble, 1,3,5-Triaza-7-phosphaadamantane-Stabilized Palladium Nanoparticles and their Application in Biphasic Catalytic Hydrogenations at Room Temperature

Water‐dispersible Pd nanoparticles stabilized by the hydrophilic cage‐like aminophosphine ligand 1,3,5‐triaza‐7‐phosphaadamantane and its N‐methyl derivative were synthesized and fully characterized in the colloidal state by TEM, and NMR and UV spectroscopy and in the solid state by X‐ray photoelectron spectroscopy and powder XRD. The three different nanoparticles obtained showed a narrow distribution range with average core sizes of 2.8, 3.2, and 3.5 nm. The activity of some of these Pd nanoparticles as catalysts in the biphasic hydrogenation of organic substrates under mild conditions has been tested, and good results and excellent reusability (up to nine catalytic runs) were obtained.