Sandra Fusco

Polar crystals in imines of 4-hydroxybenzohydrazide: a comparison between racemic and enantiomorphic crystals

Through the reaction of 4-hydroxybenzohydrazide with rac-3-methylcycplopentanone and R-(+)-3-methylcyclopentanone, racemic and enantiomorphic imines were obtained and characterized in the solid state. The racemic imine crystallizes either in the orthorhombic polar space group Pna21, and the crystal structure is polar and completely analogous to the structure of similar non-chiral imines we have recently studied, or in the monoclinic centrosymmetric space group P21/n. The enantiomorphic imine crystallizes in the monoclinic polar space group P21, but the crystal structure is actually non-polar and shows significant pseudo-centrosymmetry being quasi-isomorphous with the centrosymmetric structure of the racemic imine. The density of the enantiomorphic pseudocentric crystals is significantly higher than the polar orthorhombic racemic crystals and almost equal to the centrosymmetric racemic crystals.

Delocalized hole domains in Guanine-rich DNA oligonucleotides.

Differential pulse voltammetries of guanine-rich single- and double-stranded oligonucleotides containing up to six consecutive guanines are reported. The observed progressive lowering of the first voltammetric peak potential as the number of adjacent guanines increases unambiguously points toward the establishment of delocalized hole domains; the hole stabilization energy is ca. 0.1 eV per GG step, significantly lower than that observed for AA steps.

Orthogonal H-bonding synthons, actual and virtual structures in molecular crystals: a case study

Semicarbazides of p-substituted benzoic acids are a class of simple molecules endowed with H-bonding donor and acceptor groups capable of forming H-bonded rows along three linearly independent directions (orthogonal H-bonding synthons). When the acceptor group at the para position is strong (–NO2, –CN, –N) the same crystal packing is observed, in which three linearly independent chains are formed, and the lattice parameters are easily predictable. In the case of halogen atoms at the para position (–F, –Cl) two different packings are observed in which only one or two H-bonded chains are present. Through ab initio periodic DFT-LCAO computations, we have calculated the lattice energy and density of each semicarbazide in each of the three packings, constructing the matrices Uij and ρij of the lattice energy and density. It is found that all of the different modes of packing observed experimentally for single members of the class correspond to minima of the lattice energy and to acceptable lattice densities for every member of the class.

Insights Into Interface Treatments in p-Channel Organic Thin-Film Transistors Based on a Novel Molecular Semiconductor

Organic thin-film transistors (OTFTs) were fabricated using a novel small molecule, C6-NTTN, as the semiconductor layer in several different architectures. The C6-NTTN layer was deposited via both vacuum evaporation at different substrate temperatures and via solution-processing, which yield maximum hole mobilities of 0.16 and 0.05 cm2/

The association constant of 5′,8-cyclo-2′-deoxyguanosine with cytidine

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Solid State Separation and Isolation of Tautomers of Fused-Ring Triazolotriazoles

, respectively. Surface treatments of the substrate, insulator, and metal contacts used for OTFT fabrication employing polymer films and different self-assembled monolayers were investigated. In particular, in bottom-gate devices, the insulator surface hydrophobicity was optimized by the deposition of poly(methyl methacrylate) or hexamethyldisilazane, while in the top-gate geometry, pentafluorobenzenethiol was efficiently used to modify the substrate surface energy and to change the contact work function. Atomic force microscopy analysis was exploited to understand the relationship between the semiconductor thin-film morphology and the device electrical performance. The results shown here indicate an inverse proportionality between the mobility and the interface trap density, with parameters depending especially on semiconductor–insulator interfacial properties, and a correlation between the threshold voltage and the characteristics of the semiconductor–metal interface.

Crystal structure of N,N′-bis­(2,4-di­fluoro­benzo­yloxy)benzene-1,2:4,5-tetra­carboximide

The association of 5′,8-cyclo-2′-deoxyguanosine (cdG), a DNA tandem lesion, with its complementary base cytosine has been studied by voltammetry and NMR in chloroform, using properly silylated derivatives of the two nucleobases for increasing their solubilities. Both voltammetric data and NMR titrations indicated that the Watson-Crick complex of cytidine with cdG is weaker than that with guanosine, the difference being approximately of one order of magnitude between the two association constants.

Interface engineering in organic thin film transistors

Fine control of the tautomeric forms of [1,2,4]triazolo[3,2-c][1,2,4]triazole derivatives in acidic conditions has been achieved by acting on the electronic character of the substituent at position 7 of the heterobicycle and on the counterion. Strong electron releasing or electron withdrawing substituents lead almost exclusively to a single tautomeric form, the 1H-3H or the 2H-3H, respectively. In the case of the phenol substituent, both tautomeric forms are present in comparable amount in solution; the two tautomers can also be selectively precipitated in different crystalline salts using suitable counterions.

Strong overcrowding in dimethyl 2-(dimethylamino)terephthalate

The title compound crystallizes with half a molecule in the asymmetric unit and shows Car—H⋯F interactions in the crystal packing.

Series of O,N,O-Tridentate Ligands Zinc(II) Complexes with High Solid-State Photoluminescence Quantum Yield

A novel semiconductor, the small molecule C6-NTTN, was used to fabricate organic thin film transistors (OTFTs). Different architectures and deposition techniques were employed, together with various surface treatments of the substrate, insulator and metal contacts, whose effect is analyzed through atomic force microscopy. The aim is to investigate the relationship between the process parameters and the electrical performance, with a particular attention to the quality of interfaces between active layers. The proportionality between the charge carrier mobility and the interface trap density was studied.