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Exothermal decomposition of six (E)-(substituted azulen-1-yldiazenyl-1,2,5-oxadiazoles) was investigated by differential scanning calorimetry (DSC) under non-isothermal conditions, in inert atmosphere. From the DSC curves recorded either at various heating rates for three compounds, or at 10 K min−1 for the rest, several physical properties such as the melting temperature, melting heat, temperature and heat of decomposition were evaluated. The activation parameters of the decomposition processes were determined by analyzing their multiple curves, measured at different heating rates, using both the Friedman and Flynn–Wall–Ozawa isoconversional methods and model-fitting methods. The linear dependence of the activation energy on conversion supports the idea of the single-step nature of the decomposition processes for all examined compounds. The decomposition steps were identified from the experimental DSC curves, and their kinetic parameters were evaluated using linear regression methods. New insight into the relationship between melting and structural properties was gained if the equilibrium free energy of melting was splitted into its energetic and entropic components. The resulted thermodynamic and kinetic parameters are used to predict the hazards associated with these compounds.

As a continuation of research on 1-vinylazulenes synthesis, on their physico–chemical properties as well as on their use as colorimetric and electrochemical materials for the detection of heavy metals ions, new compounds, 4-(azulen-1-ylmethylene)-2-phenyloxazol-5(4H)-ones, are reported. The exceptional structure of azulene moiety with symmetrical electron distribution only with respect to the x-axis gives some special chemical and physical properties to compounds in which it is inserted. Various azulene-1-carbaldehydes and hippuric acids are condensed with good yields in Erlenmeyer—Plöchl reaction conditions. The obtained 1-vinylzulenes were characterized and their UV-Vis and NMR spectra were briefly discussed.

This paper deals with the study of compatibility between antihyperlipidemic agent atorvastatin calcium trihydrate (ATV) and eight pharmaceutical excipients used in the development of solid dosage forms, namely citric acid, anhydrous lactose, magnesium citrate, magnesium carbonate, sodium carboxymethyl cellulose, polyvinylpyrrolidone K30, colloidal silica and sorbitol. As investigational tools, universal attenuated total reflectance Fourier transform infrared spectroscopy and powder X-ray diffractogram patterns were used for binary mixtures of ATV with each excipient at ambient condition and then completed by subjecting the samples to thermal stress using thermal analysis (TG/DTG/HF), in non-isothermal conditions and in oxidative medium. It was shown the binary mixtures do not present interactions between ATV and excipients when stored under ambient conditions for 2 months, while under thermal stress, ATV presents interactions with sorbitol.

The paper reports on monitoring methylmalonic aciduria (MMA)-specific and non-specific metabolites via NMR urinomics. Five patients have been monitored over periods of time, things involved were diet, medication and occasional episodes of failing to comply with prescribed diets. An extended dataset of targeted metabolites is presented, and correlations with the type of MMA are underlined. A survey of previous NMR studies on MMA is also presented.

The 1H and 13C NMR spectra of several 2,6-diheteroarylvinyl heterocycles containing 4-azulenyl moiety were recorded and their proton and carbon chemical shifts were compared with those of the compounds without double bond between the heterocycles. The influence of the nature of central and side heterocycles, molecule polarization and anisotropic effects were revealed. The highest chemical shifts were recorded for the pyrylium salts and the lowest at pyridines, but in the case of the pyridinium salts, the protons chemical shifts at the central heterocycle are more shielded due to a peculiar anisotropy of the attached vinyl groups.

Preparation and microscopy characterization of polymer modified glassy carbon electrodes based on (5-[(azulen-1-yl) methylene]-2-thioxothiazolidin-4-one (L) were reported. Atomic Force Microscopy was used to investigate the morphological and mechanical properties of the deposited polyL films onto glassy carbon. The topography images of the analyzed samples exhibited the presence of some columnar shape features onto the layer surfaces. The surface roughness of the layers deposited at constant charge calculated from topography images, increased with the more positive applied potential for controlled potential electrolysis. At different charges, the roughness parameter showed the same behavior for the layers obtained applying a constant potential without having a noticeable influence on the adhesion properties on the substrate. Analysis using scanning electron microscopy shows a relatively uniform surface arrangement of the polymer and the presence of some clusters which are disturbing the planarity. PolyL chemically modified electrodes have been used for heavy metal ions detection with best results for lead.

The electrochemical characterization of 2,6-bis((E)-2-(furan-2-yl)vinyl)-4-(5-isopropyl-3,8-dimethylazulen-1-yl) pyridine has been performed by cyclic voltammetry, differential pulse voltammetry and rotating disk electrode. Modified electrodes were obtained by cycling the potential in the anodic scans or by controlled potential electrolysis (CPE) at different potentials and charges. The modified electrodes have been tested for mercury, cadmium, copper and lead ions detection.

The synthesis of pyrylium and pyridinium salts and pyridines with azulene-1-yl moieties in position 4 and two 2-heteroarylvinyl groups in positions 2 and 6 was accomplished. The pyrylium salts were obtained starting from pyranones and pyridines could be prepared from these salts by treating them with ammonium acetate. The general procedures for the synthesis of pyridinium salts, which occur with good results in less delocalized electronic systems, do not take place when applied to the above obtained pyrylium salts. Therefore, as starting material 4-(azulen-1-yl)-1-(n-butyl)-2,6-dimethylpyridinium perchlorate was used, which was condensed with heteroarylcarboxaldehydes. These compounds were completely characterized and some of their spectra were discussed. Their interaction with some metal ions was revealed, observing an affinity better than in the case of simple azulenepyridines. In the last part of the paper are presented redox potentials for several pyrylium salts and pyridines in comparison with those of the nonvinylogated derivatives.

Several vinylazulenes containing metalophilic groups were prepared as potential host molecules in ligands for metal ion detectors. The azulene-1-carbaldehyde derivatives were condensed with methylene active compounds in the presence of piperidine. The reaction is influenced by both the nature of the methylene activating groups and by the presence of the alkyl groups on the 4-,6- or 8- position of the azulene moiety. Some unusual reagents, as nitroacetate were condensed with imines activated by acetic anhydride. Several autocondensation azulenic products were evidenced in the presence of weak activated methylenes. Considerations regarding S1 and S2 absorption bands of the azulene compounds were revealed and correlated with frontier molecular orbitals. At the same time, the prepared ligands redox potentials were investigated by differential pulse voltammetry (DPV).

The phenylselanylation of azulene with PhSeCl or PhSeBr was reported. Clean electrophilic substitution of azulene in positions 1 and/or 3 occurred with the first reagent whereas with PhSeBr a complex mixture of products was generated suggesting a radicalic mechanism. The influence on the reaction route of the substituent attached at position 1 of azulene, or of the alkyl positions in alkylated azulenes was investigated. 1-Phenylselanylazulene and 1,3-bis(phenylselanyl)azulene were oxidized using sodium metaperiodate. The oxidation took place at selenium atom and afforded azulenes substituted with PhSe(O) and/or PhSe(O2) groups in positions 1 and/or 3. The magnetic and electronic spectra as well as the electrochemical oxidation and reduction potentials of the obtained products were recorded and the results were briefly discussed. .

The determination of pH values at the equivalence (isosbestic) point from the electronic spectra of several azulen-1-yl-thiazol-2-yl diazenes allowed the obtaining of their pK a values. All the studied compounds are very weak bases. The pK a values were correlated with the diazenes structure. The values for oxidation and reduction peak potentials are obtained from DPV curves. A good correlation was found between the calculated values for molecular orbitals energies and the experimental recorded data for the redox processes.

Two synthesis strategies were used for the generation of azulene-1-yl diazenes substituted at C-3 with a phenyl-chalcogenyl moiety, the synthesis of azulenes substituted at C-3 followed by azo-coupling and azulene substitution at C-3 in azulene-azo dyes. The last synthetic route seems to give more satisfactory results for the synthesis of the desired chalcogenic derivatives. Another target of this study was to investigate the changes induced by the phenyl-chalcogenic substitution on the NMR and UV-vis spectra, and also to compare this effect with the one exerted by halogen atoms and by strongly electron donating groups such as AcNH or PhCOO. Whereas the latter groups exhibit a strong influence on the NMR and UV-vis spectra, PhS, PhSe, or PhTe groups as well as halogen atoms produce only a small effect because of the moderate change in electron distribution over the entire molecule.

Pyranylium perchlorates with azulen-1-yl moiety in 4-position and thiophen-2-yl or furan-2-yl in 2 and 6-positions were obtained by the substitution of 4-chloro corresponding salts with azulenes. The pyranylium salts are used as starting materials for the synthesis of pyridine and pyridinium salts. The products were characterized and for pyridines pKa was spectroscopically determined. Several attempts were made for pyridine complexation with metal cations as Hg2+ or Ag+. J. Heterocyclic Chem., (2011).

Acidity and redox potentials of a series of substituted azulen-1-yl-benzothiazol-2-yl diazenes are correlated with several theoretical parameters. From the electronic spectra of the dyes recorded at different pH, the derived pKa values correlate well with para Hammett-constants. The experimental oxidation and reduction potentials, as determined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), are in good agreement with the calculated frontier orbital energies, for the studied dyes.

3- and 4-[(Azulen-1-yl)-azo]-azo-benzenes were obtained in good yields using the buffered coupling reaction between several alkyl-substituted azulenes and diazotized phenylazo-phenylamines in dichloroacetic acid. The coupling products were characterized and the recorded electronic spectra are discussed. The isosbestic points obtained by protonation enabled the determination of their p K a values.

The 3+2 cycloaddition reaction of 1-(3-nitrophenacyl)-1,10-phenanthrolinium ylide 4 with activated alkynes gave pyrrolo(1,2-a)(1,10)phenanthrolines 7a-e. The reaction of N-ylide 4 with DMAD, under controlled conditions, gave regioselectively the primary cycloadduct trans-5a which, in the presence of triethylamine, rearranged regio- and stereoselectively to trans-6a. Evidence for the helical chirality of pyrrolophenanthrolines 7b-e was obtained by NMR spectroscopy.

The synthesis, characterization and X-ray crystal structure of 2-(4-chloro-phenyl)-7-methylpyrrolo[1,2-b]pyridazine are reported. The compound crystallizes in the space group P2(1)/c (No.14) with a =3.8568(1), b = 11.0690(3), c = 26.4243(7) A, beta =92.777(1) degrees and Z = 4. Accurate molecular parameters for the novel heterocyclic system were obtained from intensity data collected at 113K. The molecule assumes a planar conformation in the crystal and the packing is based on pi-pi stacking with interplanar spacing 3.400 å, typical of aromatic molecules with potential for displaying useful optical properties.

Pyranylium perchlorates with azulen-1-yl moiety in 4-position and thiophen-2-yl or furan-2-yl in 2 and 6-positions were obtained by the substitution of 4-chloro corresponding salts with azulenes. The pyranylium salts are used as starting materials for the synthesis of pyridine and pyridinium salts. The products were characterized and for pyridines pKa was spectroscopically determined. Several attempts were made for pyridine complexation with metal cations as Hg2+ or Ag+. J. Heterocyclic Chem., (2011).

(Azulen-1-yl)carboxylic acids 3-substituted by 2-(thiazol-2- or 3-yl)-ethenyl groups and their esters were synthesized starting either from the corresponding 1-azulenyl-2-thiazolyl-ethenes, 3, or from methyl 3-formyl-azulen-1-yl carboxylate, 7. The ethenes 3 were phosgenated in an electrophylic reaction followed by the reaction with water or alcohol. The aldehyde 7 was transformed in Schiff base which was reacted with corresponding thienylacetic acid to generate the ester 6b. The products characterization and considerations about the obtained compounds structure are reported.