Charge transfer complexes of 2,4,6-tricyano-s-triazine with tetrathiafulvalene (TTF) and N,N,N' ,N'-tetramethyl-p-phenylenediamine (TMPD)

Journal ArticleReaction of 2,4,6-tricyano-s-triazine (TCT) with tetrathiafulvalene (TTF) and N,N,N',N'-tetramethylp-phenylenediamine (TMPD) leads to 1 : 1 charge transfer complexes. The crystal structures of the TTF[TCT], as well as the decomposition product due to hydrolysis of the [TMPD][TCT], i.e. HTMPD]+[2,4-dicyano-6-oxy-s-triazine]-, are reported and spectroscopically characterized

Stereospecific winding of polycyclic aromatic hydrocarbons into Trinacria propellers

The stereospecific trimerization of enantiomerically-pure binaphthols with hexakis(bromomethyl)benzene gives access in one step to enantiomerically-pure molecular propellers, in which three binaphthyl rings are held together through dioxecine rings. X-Ray diffraction analysis revealed that three out the six naphthyl moieties are folded in a (EF)3-type arrangement held by three intramolecular C-H…π interactions. This slips outward the three remaining naphthyl rings in a blade-like fashion, just like in three-folded propeller components. This peculiar conformation shows striking similarity to the mythological Sicilian symbol of Trinacria, from which the name "trinacria propeller" derives. The propeller conformation is also preserved in chlorinated solutions, as displayed by the presence of a peak at 4.7 ppm typical of an aromatic proton resonance engaged in a C-H…π interaction. The denaturation of the propeller-like conformation is obtained at high temperature, corresponding to activation energy for the ring inversion of ca. 18.2 kcal mol-1. Notably, halide-functionalized molecular propellers exposing I-atoms at the leading and trailing edges could be prepared stereo- and regiospecifically by choosing the relevant iodo-bearing BINOL derivative

On the relation between carbonyl stretching frequencies and the donor power of chelating diphosphines in nickel dicarbonyl complexes

The relation between spectroscopic observables and the detailed metal- ligand bonding features in chelation complexes is addressed using both experimental and state-of-the-art theoretical and computational methods. We synthesized and characterized a set of six nickel dicarbonyl complexes of general formula [Ni(CO)(2)(PP)], where PP is an atropoisomeric chelating diphosphine ligand. The analysis of the obtained experimental data and the basicity and oxidative potentials of the free ligands suggests a close relation between the donor ability of the chelating ligand and the carbonyl stretching frequencies observed in the complexes. We then use theory to unravel the detailed mechanisms of chelation-bond formation in terms of partial charge flows between the molecular orbitals of the fragments. By extending the promising, recently published natural orbitals for chemical valence/ charge displacement (NOCV/CD) analysis scheme we provide a thorough, quantitative description of the several charge fluxes following the metal-ligand bond formation and demonstrate that the carbonyl stretching frequencies in the considered complexes selectively respond to the sigma-donation charge flow from the phosphorus lone pairs of the ligands, with the frequency shift being in quantitative correlation with the extent of the ligand-to-metal charge transfer

Unexpectedly high second-order nonlinear optical properties of simple Ru and Pt alkynyl complexes as an analytical springboard for NLO-active polymer films

The unexpectedly high quadratic hyperpolarizability values of simple Ru and Pt alkynyl complexes have been measured by the EFISH technique, and this prompted us to investigate their potential as molecular building blocks for composite films with second harmonic generation properties

Application of density functional theory in the synthesis of electroactive polymers

A wide range of conjugated organic compounds undergo anodic electropolymerisation to produce polymers of high conductivity. However, electrooxidation does not always result in the formation of electroactive materials, since some reactions produce insulating films or soluble oligomers. Density functional theory (DFT) has been used to predict the outcome of electropolymerisation reactions by calculating the unpaired electron π-spin density distribution of monomeric radical cations, in order to determine coupling positions in the resultant polymers. π-Spin densities calculated for pyrrole, thiophene and (E)-stilbene are found to be in good agreement with experimental values. DFT has been used to investigate the low conductivity and redox inactivity of poly[(E)-3-styrylthiophenes] and poly[(E)-2-styrylheterocycles]. High positive spin densities at the alkene spacer linkage in the corresponding monomeric radical cations were found, suggesting crosslinking of the polymers via the double bond. In contrast, electroactive polymers of improved conductivity are formed from the electropolymerisation of some (Z)-2-α,β-diarylacrylonitriles. For these monomers, DFT calculations show the positions of highest spin density to be located at the α-positions of the heterocyclic rings, suggesting the presence of α,α′-linked monomeric couplings necessary for electroactivity

Descubriendo la arquitectura de sistemas de software híbridos: un enfoque basado en Modelos i*

La mayoría de sistemas de software modernos se construyen integrando componentes de diversa naturaleza (comerciales, código libre, componentes legados, etc.), formando arquitecturas híbridas. La construcción de este tipo de sistemas se caracteriza por la adquisición de diversos componentes a proveedores externos a la organización que se integran con algún software hecho a medida. La correcta aplicación de este enfoque requiere la temprana identificación de los servicios que el sistema deberá brindar y su agrupación en dominios atómicos (los actores del sistema), que serán posteriormente remplazados de una manera “oportunista”, por los componentes más apropiados, independientemente de su naturaleza y origen. En este artículo abordamos este aspecto y proponemos un método basado en la utilización de modelos i*, que permite identificar los actores del sistema y su estructuración en una arquitectura de partida. El método es ilustrado con un caso práctico en una empresa de telecomunicaciones.Peer ReviewedPostprint (published version

Panoramic Overview on the Enantioselection Performance of Inherently Chiral Surfaces: a Comparison between Systems with Different Atropisomeric Cores and Stereogenic Elements

Enantiorecognition is a key issue in advanced analytical chemistry, particularly concerning the biological and pharmaceutical field. Enantiomeric molecules, being mirror-image structures, have identical physico-chemical scalar properties, but opposite pseudo-scalar ones. When interacting with a racemic probe, chiral molecules are able to recognize the enantiomers through diasteromeric interactions. Similarly, chiral electrodes are required for enantioselective electroanalysis, and the development of "intelligent" electrodes capable of discriminating enantiomers, in particular molecules of biological and pharmaceutical importance, remains as one of the major challenges in electroanalysis. We have recently proposed the first synthetic inherently chiral electrode surfaces able to neatly discriminate as separate peaks (in terms of potential values) the antipodes of model chiral probes, also drugs, both as enantiopure and racemate. [1-2] We have also verified the general validity of the inherently chiral concept, which does not depend from the chemical nature of the atropisomeric scaffold, testing chiral surfaces electrooligomerized from starting monomers with different molecular design (i.e. bithiophene, bibenzothiophene, biindole and paracyclophane cores) and different stereogenic elements (stereogenic axis vs helix vs plane). In order to fully elucidate the enantioselection capability of all of these heteroaromatic systems we propose a detailed comparison (an example in Figure) of our inherently chiral surfaces with different atropisomeric core vs thiahelicene-based films vs \u201ctwo floor\u201d paracyclophanic oligomers. Figure. Enantioselection properties of inherently chiral oligomers with bibenzothiophene and biindole units towards L- and D-DOPA probes. The support of Fondazione Cariplo/Regione Lombardia "Avviso congiunto per l\u2019incremento dell\u2019attrattivit\ue0 del sistema di ricerca lombardo e della competitivit\ue0 dei ricercatori candidati su strumenti ERC - edizione 2016\u201d (Project 2016-0923) is gratefully acknowledged. References: [1] F. Sannicol\uf2, S. Arnaboldi, T. Benincori, V. Bonometti,R. Cirilli, L. Dunsch, W. Kutner, G. Longhi, P. R. Mussini, M. Panigati, M. Pierini, S. Rizzo, Angew Chem. Int. Ed., 53 (2014) 2623-2627. [2] S. Arnaboldi, T. Benincori, R. Cirilli, W. Kutner, M. Magni, P. R. Mussini, K. Noworyta, F. Sannicol\uf2, Chem. Sci., 6 (2015) 1706-171

Analysing Security in Information Systems

The last few years there is a tendency to integrate security issues during the development of information systems with the aim to develop more secure information systems. In this paper we propose an analysis, based on the measures of criticality (how critical a component of the system is) and complexity (represents the effort required by the components of the system to achieve the requirements that have been imposed to them), which aims to identify possible bottlenecks of an information system with respect to security. An integrated health and social care information system is used as a case study throughout this paper

Temporal multi-sensor system for voltammetric recognition of l- and d-tryptophan enantiomers based on generalized principal component analysis

© 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. The results of a quantitative reading of the cyclic voltammetry behavior of the tryptophan (Trp) enantiomers deposited on an electrochemically activated glassy carbon electrode (GCE) are presented. A combined method for "reading" the analytical signals based on the modified Fourier transform and GPCA was applied. It allows a quantitative description of a derivative (dJ/dU) of the measured VAG. This combined method essentially increases the limits of conventional PCA and can be applied to a wide set of electrochemical data. This combined method allows the differentiation and quantitative description of signals governed by the different structures of l- and d-Trp(s) in aqueous solutions

Synthesis and crystallographic evaluation of diazenyl- and hydrazothiazoles. [5.5] sigmatropic rearrangement and formation of thiazolium bromide dihydrate derivatives

In this investigation the synthesis of diazenylthiazoles (3a-e) by the reaction of arylthiosemicarbazides with omega-bromoacetophenones via Eschenmoser-coupling reaction in acetonitrile and equimolar amounts of triethylamine and triphenylphosphine. Upon heating 1,4-disubstituted thiosemicarbazides with omega-bromoacetophenones in absolute ethanol, hydrazothiazoles (16a-i) were precipitated. On the other hand, the reaction of arylthiosemicarbazides with omega-bromoacetophenones in refluxing ethanol yielded 2-amino-5-[4-aminophenyl]-4-phenylthiazolium bromide dihydrate derivatives (19a-g) via [5.5] sigmatropic shift. The studied products were further characterized by IR, H-1 NMR, C-13 NMR and mass spectrometry. X-ray single crystal of 3a and 16h showed that, the molecules crystallized in the triclinic crystal system, space group P2(1)/c. Whereas the X-ray single crystal of 19b showed the molecule crystalized in orthorhombic, space group P2(1)2(1)2(1). In the crystal of 19b, the lattice water and bromide ion associated through hydrogen bonded with thiazole-NH2. (C) 2018 Published by Elsevier B.V.Peer reviewe