Antonio Carella

Two-photon patterning of a polymer containing Y-shaped azochromophores

We report on the patterning of the free surface of azo-based polymer films by means of mass migration driven by one- or two-photon absorption. A symmetric donor-acceptor-donor structured Y-shaped azochromophore is specifically synthesized to enhance two-photon absorption in the polymer. The exposure of the polymer film to a focused laser beam results in light-driven mass migration for both one- and two-photon absorptions. Features with subdiffraction resolution (250 nm) are realized and the patterning dynamics is investigated as a function of the light dose. Furthermore, functional photonic structures, such as diffraction gratings with periods ranging between 0.5 and 2.0 μm, have been realized.

Outstanding Poling Stability of a New Cross-Linked Nonlinear Optical (NLO) Material from a Low Molecular Weight Chromophore

In this paper we report the synthesis and characterization of a trihydroxylated nonlinear optical (NLO) azochromophore and its functionalization with 2,4-tolylendiisocyanate (TDI) to give an amorphous mixture of isomers that was used as a starting compound for the preparation of cross-linked electro-optic (EO) thin films. An unedited type of thermal cross-linking reaction was used, exploiting the reactivity of isocyanate groups themselves in the presence of N,N-dimethylacetamide, without the addition of any hydroxylated comonomer as usual in the preparation of polyurethanes. Thin films were prepared by spin coating and corona poled during thermal cross-linking. A d(33) value of 33 pm/V was obtained by second-harmonic generation (SHG) measurements on poled films, and an excellent stability of SHG signal was shown upon aging at 130 °C and during dynamic thermal stability measurements.

Synthesis and second order nonlinear optical properties of new chromophores containing 1,3,4-oxadiazole and thiophene rings

We report the synthesis and physico-chemical characterization, including molecular second order nonlinear optical properties by the EFISH technique, of three new heterocycle based push–pull chromophores. Two chromophores contain the five membered 1,3,4-oxadiazole ring, the third a thiophene ring. The chromophores also contain azo or stilbene bridges between conjugated aromatic rings and are functionalized for covalent incorporation into polymer chains. The maximum observed μgβ is 1350 × 10−48 esu for the thiophene chromophore in conditions far from resonance enhancement (fundamental laser wavelength 1.907 µm). The crystal structure of one oxadiazole chromophore is also discussed.

Competitive H-bonding synthons in organic hydrazides

A theoretical, statistical and crystallographic analysis of the H-bonding patterns in organic monohydrazides is presented. The theoretical analysis has shown that the conformation of the hydrazido group with the two amino H atoms staggered with respect to the amide bond is energetically more favoured. Assuming this conformation, four intermolecular H-bonding patterns can be reasonably foreseen, two forming chains, C(4) and C22(8), and two forming rings, R22(10) or R22(6). The frequency of occurrence of the four patterns in the set of crystal structures of hydrazides retrieved from CSD was evaluated. In particular, it was found that the four motifs are present in 79% of the total number of crystal structures of hydrazides found in CSD. Finally, the crystal structures of four new benzohydrazides having additional H-bonding donor or acceptor groups in the para position are presented and discussed with reference to the H-bonding patterns.

Novel High Glass Transition Temperature Polyurethanes Functionalized with Efficient CT Chromophores for Second Order NLO Applications

ABSTRACT In this paper we describe the synthesis of a new class of high glass transition temperature polyurethanes functionalized with two quasi 1D charge transfer dyes. The polymers are soluble in several organic solvents and can be processed into thin films by spinning technique. The polymers were synthesized in view of their application in second order nonlinear optics for optical signal transmission. The active chromophores, exhibiting large first hyperpolarizabilities β(− 2ω;ω, ω) were poled by the corona poling technique. The kinetics of poling and of relaxation were studied by second harmonic generation technique.

Biostability enhancement of oil core - polysaccharide multilayer shell via photoinitiator free thiol-ene 'click' reaction.

Layer-by-layer of polyelectrolytes has emerged as one of the easiest and most controlled techniques to deposit ultrathin polymer layers mainly driven by electrostatic interactions. However, this kind of interaction results to be weak and easily breakable in physiological environment. Here we report on the preparation of nanocapsules completely made of natural biomaterials: a lipophilic core (soybean oil and egg lecithin as surfactant) as nanometric template and a polysaccharide-based multilayer shell (glycol chitosan and heparin) covalently cross-linked. We first modified glycol chitosan with a thiol moiety and heparin with an alkene moiety, respectively, and then we built a polymer multilayer film with a covalent cross-linkage among layers, exploiting the light initiated thiol-ene reaction, known as click chemistry. We showed the possibility to perform the covalent cross-linkage without any photoinitiator or metal catalyst, thus avoiding cytotoxic effects and further purification steps. The so realized nanocapsules resulted to be stable and completely biocompatible and, therefore, of interest for the biotechnology fields, mainly for drug delivery.

A topotactic transition in a liquid crystal compound

The title compound, bis(4-butyloxyacetophenon)azine, exhibits a rich phase behavior. It has two different crystal phases and one liquid crystal phase before transition to the isotropic liquid phase. The liquid crystalline phase is nematic. All the phase transitions of the compound are reversible. In particular, the solid–solid transition at 83 °C is single-crystal-to-single-crystal as proven by optical and electron microscopy and X-ray diffraction analysis and it shows a remarkable degree of reversibility; single crystals can undergo several cycles of transition between the two phases without any damage. The crystal phase stable at lower temperature has been fully characterized by single crystal X-ray analysis. It shows an arrangement of the molecules in layers in the plane (a, b), with the layers piled up along c without interdigitation of the alkyl tails of molecules belonging to consecutive layers. The crystal phase stable at higher temperature is disordered.

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

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.

Dipentyl 2,6-di­amino­benzo[1,2-b:4,5-b′]di­furan-3,7-di­carboxyl­ate

The title compound, C22H28N2O6, crystallizes with one half-molecule in the independent unit, the molecule being located on an inversion centre. The penthyl groups are in the all-trans conformation and an almost planar conformation of the whole molecule is observed [maximum deviation from the least-squares plane through all non-H atoms is 0.0229 (17) Å for an N atom]. The amino groups are involved in intra- and intermolecular hydrogen bonds. Intramolecular hydrogen bonding involving the amino group and ester carbonyl helps to lock the syn conformation of the ester with respect to the amino group. In the crystal, N—H⋯O hydrogen bonding involving the amino group and the furan and ester carbonyl O atoms self-assembles the molecules into a two-dimensional hydrogen-bonded network parallel to (010) that displays interdigital packing sustained by alkyl–alkyl interactions.

Evaluating the biological properties of synthetic 4-nitrophenyl functionalized benzofuran derivatives with telomeric DNA binding and antiproliferative activities

Four 4-nitrophenyl-functionalized benzofuran (BF1, BF2) and benzodifuran (BDF1, BDF2) compounds were synthesized by a convenient route based on the Craven reaction. All the compounds underwent a detailed chemical-physical characterization to evaluate their structural, thermal and optical properties. An investigation on the therapeutic potential of the reported compounds was performed by analyzing their antiproliferative activity on prostatic tumour cells (PC-3). In both classes of compounds, anticancer potential is in direct correlation with the lipophilicity. From our study it emerged that antiproliferative activity was higher for benzofuran derivatives as compared to benzodifuran systems. Moreover, we report a mechanistic study relative to the most promising molecule, i.e. the apolar benzofuran BF1, that relates the antiproliferative properties found in our investigation to its ability to bind telomeric DNA (proven by CD and fluorescence techniques on tel22 G4 DNA), and highlights its unexpected impact on cell cycle progression.