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Intelligent food packaging systems register and monitor food quality through data carriers, sensors or indicators. Food spoilage often leads to pH variations which can be easily evidenced through a colorimetric pH indicator. The objective of this study was to obtain and characterize intelligent pH indicator films based on biopolymers, namely chitosan and polyvinyl alcohol, doped with a new bio-inspired synthetic dye. UV–Vis, FTIR and 1D and 2D NMR techniques were used to characterize the xanthylium dye. The pH-dependent photochromic properties of the synthesized compound were confirmed through a UV–Vis spectroscopy study. The indicator films were obtained by using the solvent casting technique, and their optical and thermal properties were evaluated. When subjected to pH variations in aqueous solutions and in milk stored at improper temperatures, the films showed color changes. The thermal properties of the dye-containing films were evaluated through TG/DTG analysis. It was found that the inclusion of the dye does not change the thermal behavior of the films compared with that of the dye-free chitosan, PVA and chitosan/PVA blended films.

The goal of the study was to evaluate the influence of the solvent properties on the crystal characteristics of β-cyclodextrin (β-CD) recrystallized from alcohol-water solvent mixtures, with possible applications for the preparation, purifying and complexation of β-CD. For the first time, structure-property relationships (QSPRs) between the hydrophobicity of alcohols or dielectric constant of solvents used for recrystallization of β-CD and its properties (such as crystallinity index, CI) have been obtained. Recrystallized β-CD from water and C1-C4 alcohol-water solutions provide β-CD with higher CI values of 99.4(±5.9)% for ethanol-water (1:4, v/v) as recrystallizing system. This property has a parabolic variation with the logP (octanol/water partition coefficient) of the alcohol (r2 = 0.998). Solvent parameters also influence the β-CD crystal characteristics, as was demonstrated by X-ray diffractometry refinement, infrared spectroscopy and thermal analyses.

Photodynamic therapy represents an alternative and/or adjuvant method for the treatment of superficial tumors; this way, there is an increased interest regarding the design of new photosensitizers with improved properties. The aim of the paper is to study the interactions among five substituted porphyrins and some rhombellanes (seven cube-rhombellane homeomorphs, C-rbl, with amide structures). The aforementioned porphyrins have been characterized and have been docked to the surface of the rhombellanes; comparisons with the results obtained for fullerene C60 have been performed. The best binding affinities have been obtained for the fluoro-substituted porphyrin docked on the larger rhombellane structures. The results outline that the hydrophobicity of the ligands plays an important role and represents a good indicator of searching for porphyrins with hydrophobic character for future investigations. This work is licensed under a Creative Commons Attribution 4.0 International License.

New copolymers of ε-caprolactone with three hydroxy-fatty acids, 12-hydroxy stearic acid, 16-hydroxyhexadecanoic acid and ricinoleic acid, were synthesized by catalytic polyesterification. The reactions were carried out in solvent-free systems and in organic solvents as well, using tin(II) 2-ethylhexanoate as catalyst, at different temperatures and molar ratios of the comonomers. Cyclic and linear polymeric products with medium molar weight of about 2000 Da have been synthesized and their chemical structures were confirmed by FT-IR, NMR and MALDI-TOF MS analysis. The synthesis parameters were optimized and the ε-caprolactone/hydroxy acid molar ratio was set as 5:1, according to mass spectrometry results. The biodegradability of the newly synthesized polymers was studied in the presence of Candida antarctica B lipase in phosphate buffer solutions (pH=7.4), at 37°C. The weight-loss profile emphasized the degradation of the 16-hydroxyhexadecanoic acid based polymer samples at more than 50% of their initial weight in 18 days of incubation in the presence of the lipase. The composition of the degradation products was assessed using the GC-MS technique and displayed residues of the comonomers moieties.

The electrode potential of cyanidin was determined both by experimental (cyclic voltammetry) and theoretical methods, at HF/6-311G(d) level of theory. An isodesmic reaction scheme, involving 1,2-benzoquinone as reference molecules, has been proposed for the computation of electrode potential of cyanidin. The results of the ab initio computations are in reasonable agreement with available experimental measurements; the differences between experiment and theory are within the range of 0.02-0.05V. Geometric parameters of the six more stable conformers of cyanidin are computed, as well as properties like atomic charges and contribution to the HOMO (Highest Occupied Molecular Orbital) energies of each hydroxyl group of the cyanidin.

The stability and aromaticity of 36 heterobenzenes containing group 15 elements were evaluated at the B3LYP/6-311+G(d,p) level of theory. Stability evaluation was performed based on the enthalpies of formation calculated from imaginary reactions and on the absolute hardness reactivity descriptor. The aromaticity was investigated by means of geometric (Bird, Harmonic Oscillator Model of Aromaticity (HOMA) indices), energetic (aromatic stabilization energy), and magnetic criteria (nucleus-independent chemical shifts [NICS] index). Also, within the conceptual density functional theory (DFT) theory, reactivity-based descriptors (highest occupied molecular orbital and lowest unoccupied molecular orbital [HOMO—LUMO] energy gap, absolute hardness, electrophilicity) were computed. The results led to the conclusion that all heterobenzenes exhibit aromatic character, which generally decreases from N to As containing compounds and from one to six substituted CH groups.

The aromatic character of three different flowers of general formula [n:(p i,p j)n/2], namely [8:(5,7)4], [8:(6,6)4] and [8:(5,6)4], has been evaluated by means of geometric (HOMA index), energetic (heats of formation) and magnetic criteria (NICS index, exaltation of magnetic susceptibility). Also, the reactivity descriptors within the DFT approach -absolute hardness, electrophilicity, Fukui functions — have been computed. All the different methods used for estimating the aromaticity led to a unitary conclusion. Two fullerene structures, patched by the most stable 8-Sumanene flower, have been designed and evaluated by means of ab initio computations

To improve the quality requirements for copper deposits, the influence of some inhibition agents added to the acidic copper bath has been studied. Several aromatic nitrogen compounds have been tested as inhibition agents, such as aniline, N-methylaniline, N-ethylaniline, N,N-dimethylaniline (DMA), and N,N-diethylaniline (DEA). The electrochemical behavior of these organic additives and the most relevant aspects of the electrochemical behavior of copper in acid solutions have been analyzed by cyclic voltammetry. At the same time, a correlation between voltammetric data and molecular properties of protonated amines obtained by molecular modeling has been performed. The morphology of the copper deposits obtained in the absence and presence of organic compounds has been studied by scanning electron microscopy. An improvement of the roughness degree and crystallite size upon addition of aromatic amine has been found. Best results were obtained for DMA and DEA working at room temperature (25 ± 0.1 °C) and 200 A m−2 current density, in 1 mol L−1 sulfuric acid solution with 50 g L−1 Cu2+.

A theoretical study regarding the evaluation of the antioxidant character of three of the most wide-spread anthocyanidins (cyanidin, delphinidin and malvidin) was carried out at ab initio level. Different parameters (bond dissociation enthalpy, ionization potential, proton affinity, and electron transfer enthalpy) were computed for each OH group of the compounds in order to predict their antioxidant capacity. Several molecular descriptors based on frontier molecular orbital theory (hardness, electrophilicity, frontier charge density) were also calculated, as well as the atomic charges corresponding to the O atoms of the hydroxyl groups.

Benzylamine catalytic effect on the cathodic hydrogen evolution in acid aqueous solution has been studied on copper electrode. Experimental results obtained by voltammetric techniques emphasize that the presence of benzylamine in 1 M sulfuric acid solution enhances the hydrogen evolution reaction (HER). In such a solution, benzylamine is protonated and exists as benzylammonium cation. Kinetic parameters of HER have been determined, observing a significant increase of the exchange current in the presence of benzylamine. Also, a decrease of the cathodic transfer coefficient has been noticed. Activation energy for HER has been computed on the basis of the Arrhenius plots. In the presence of benzylamine the activation energy was 33.0 kJ mol −1 , whereas without benzylamine a greater value was obtained: 94.6 kJ mol −1 . The catalytic effect of benzylamine was confirmed by electrochemical impedance spectroscopy. The considerable diminution of the double layer capacity is a valid proof of the strong adsorption of benzylamine at the Cu – sulfuric acid solution interface, while the reduction of the charge transfer resistance is a symptom of the enhancement of HER. Ab initio molecular modeling of benzylammonium ion showed that, due to a high value of the dipole moment, the molecules are oriented in the most favorable position for the charge transfer reaction, i.e., with the protonated amino group facing toward the electrode.

Hydrolysis reaction of 2-dichloromethylbenzimidazole with aqueous diethylamine was studied both experimentally and theoretically. The behavior of two other aromatic dihalides (dibromomethylbenzene and 2-fluoro-dichloromethylbenzene) was also theoretically studied, starting from already known experimental results. The theoretical calculations of local DFT-based descriptors (i.e., Fukui function, electrophilicity index) successfully account for the different reactivity of the three aromatic dihalides in the same hydrolysis reaction. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Hyperdiamonds are covalently bonded carbon phases, more or less related to the diamond network, having a significant amount of sp3 carbon atoms and similar physical properties. Many of them have yet a hypothetical existence but a well-theorized description. Among these, the diamond D5 was studied in detail, as topology, at TOPO GROUP CLUJ, Romania. The theoretical instrument used was the Omega polynomial, also developed in Cluj. It was computed in several 3D network domains and analytical formulas have been derived, not only for D5 but also for the well-known diamond D6 and other known networks.

Shape is a very important molecular feature for describing ligand molecules interacting with receptor, and other various complex chemical and biological processes. During the last years, there is a strong interest in developing several molecular shape descriptors. In this chapter we present our attempts for deriving van der Waals (vdW) shape molecular descriptors from two size molecular descriptors – the molecular vdW volume (VW) and the molecular vdW surface (SW). The ovality Θ iD , i = 1,2,3 descriptors measure the deviation of the shape of a molecule from a spherical form in one-, two-, and three dimensions, respectively, whilst the {δ,G} molecular shape parameters take into consideration the cylindrical shape of a molecule or substituent. The application of these molecular descriptors in the study of the toxicity of a series of aliphatic amines on the protozoan ciliate Tetrahymena pyriformis (Θ iD ) and for the correlation of rate constants of bimolecular nucleophilic substitution, acid-catalyzed hydrolysis of esters and esterification reactions (δ) is also reported in this chapter. The MTD (minimal topologic difference) method allows a receptor site mapping in the frame of a series of bioactive compounds. The MVD (minimal volume difference) method is an improved variant of the MTD method, which takes into account the 3D extension of a molecule. These methods are described here in some detail. The results obtained in the study of anti-carcinogenic activity of some retinoids and in the inhibition of carbonic-anhydrase (CA) by a series of sulfonamides are also presented in this chapter.

Stability measures, such as the total energy and the HOMO-LUMO gap, calculated at the Hartree-Fock and DFT levels of theory, and the aromatic character of five circulenes/flowers with a hexagonal core and petals consisting of 5-, 6- and 7-membered rings are investigated. Geometric (HOMA) and magnetic (NICS) criteria are used to estimate the local aromatic character of every ring of the investigated circulenes. The local aromaticity of the coronene and sumanene patches in two tetrahedrally spanned fullerenes were calculated and compared with the HOMA and NICS values of the corresponding isolated circulenes.