M. Judith Percino

Crystal structure of 2,6-distyrylpyridine

We have crystallized the 2,6-distyrylpyridine compound from the condensation reaction of the 2,6-dimethylpyridine with benzaldehyde (at 135°C) to obtain a model compound having three rings joined with two double bonds in order to understand the structure of poly(2,6-styrylpyridine) and poly(2,6-pyridinediylvinylene) and their formation mechanism. The X-ray structure shows that the title compound belongs to the trigonal crystal system, space group P32, and with unit cell dimensions a = 15.5637 (12) Å, c = 5.7852 (13) Å. From the molecular structure it was clear that the substituents on double bonds were in the trans position, which was in agreement to the IR and 1H NMR results. The molecule is planar and forms stacks in the crystal. The molecular structure of 2,6-distyrylpyridine has two trans double bonds between the rings and therefore it can be in three nonequivalent conformations. The preferred conformation showed by X-ray crystallography can be the result of weak steric interactions between the double bond trans hydrogens and the nearby hydrogens of the phenyl or pyridyl groups. The crystal structure, and IR and 1H NMR results are currently reported.

Spectroscopic characterization of halogen- and cyano-substituted pyridinevinylenes synthesized without catalyst or solvent

An efficient Knoevenagel route using green chemistry conditions was applied for the synthesis of halogen- and cyano- substituted pyridinevinylene compounds. Absorption and fluorescence emission spectra of these conjugated compounds were recorded and compared in order to evaluate the effect of substituents on the electronic properties of pyridinevinylene compounds. The substituents studied were terminal Cl and F, two or three aromatic rings, as well as a cyano group attached to a C=C double bond. The compounds synthesized are: (E)-2-(4-fluorostyryl)pyridine, (E)-2-(4-chlorostyryl)pyridine, (E)-4-(4-chlorostyryl)pyridine, 2,3-diphenylacrylonitrile, 3-phenyl-2-(pyridin-2-yl)acrylonitrile, 3-phenyl-2-(pyridin-3-yl)acrylonitrile, 2-phenyl-3-(pyridin-2-yl)acrylonitrile, 3,3′-(1,4-phenylene)bis(2-phenylacrylonitrile), 3,3′-(1,4-phenylene)bis(2-(pyridin-2-yl)acrylonitrile), and 3,3′-(1,4-phenylene)bis(2-(pyridin-3-yl)acrylonitrile). The solvent-free method used in this work allows obtaining each compound by controlling the reaction temperature. The compounds were characterized by infrared spectroscopy and 1H-NMR spectroscopy.

Synthesis, optical, and spectroscopic characterisation of substituted 3-phenyl-2-arylacrylonitriles

The Knoevenagel condensation between aldehydes and substrates with active methylene groups was applied to synthesise a series of 3-(4-substituted phenyl)-2-arylacrylonitriles (aryl = phenyl or pyridyl). Chloro-, fluoro-, or dimethylamino-substituted aryls and a cyano group attached to the double bond of acrylonitrile were studied. Previous studies showed that the condensation products were E isomers. The compounds synthesised were: 3-(4-chlorophenyl)-2-phenylacrylonitrile, 3-(4-chlorophenyl)-2-(pyridin-2-yl)acrylonitrile, 3-(4-chlorophenyl)-2-(pyridin-3-yl)acrylonitrile, 3-(4-chlorophenyl)-2-(pyridin-4-yl)acrylonitrile, 3-(4-fluorophenyl)-2-phenylacrylonitrile, 3-(4-fluorophenyl)-2-(pyridin-2-yl)acrylonitrile, 3-(4-fluorophenyl)-2-(pyridin-3-yl)acrylonitrile, 3-(4-fluorophenyl)-2-(pyridin-4-yl)acrylonitrile, 3-(4-dimethylaminophenyl)-2-phenylacrylonitrile, 3-(4-dimethylaminophenyl)-2-(pyridin-2-yl)acrylonitrile, 3-(4-dimethylaminophenyl)-2-(pyridin-3-yl)acrylonitrile, and 3-(4-dimethylaminophenyl)-2-(pyridin-4-yl)acrylonitrile. Structures were confirmed by IR, MS, and NMR spectral data. Molar absorption coefficient, absorbance, and fluorescence emission spectra were compared in order to evaluate the effects of substituents on phenyl and the position of nitrogen in pyridine moiety on the electronic properties of acrylonitrile derivatives prepared.

New o- and p-methacryloylaminophenylarsonic monomers. Useful building units for water-soluble polymeric and nonlinear optical materials

New o- and p-methacryloylaminophenylarsonic monomers and their sodium salts were prepared from the condensation reaction of o- and p-aminophenylarsonic acids and methacryloyl chloride for obtaining water-soluble cationic exchange polymeric materials by radical polymerization of such monomers. Noteworthy features were the coordination of some metal ions with the o- and p-methacryloylaminophenylarsonic acid (o- and p-MAPHA) monomers by interchange of the corresponding salts and the good nonlinear optical (NLO) properties displayed by these compounds. The structures of the new monomers were determined by mass spectrometry and IR, 1H-NMR, and 13C-NMR spectroscopy.

Synthesis, Characterization and Photophysical Properties of Pyridine-Carbazole Acrylonitrile Derivatives

We synthesized three novel highly fluorescent compounds, 2-(2’-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, 2-(3”-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, and 2-(4-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile by Knoevenagel condensation. The first two were synthesized without solvent in the presence of piperidine as a catalyst; the third was synthesized without a catalyst and with N,N-dimethylformamide as a solvent. In solution, the molar absorption coefficients showed absorptions at 380, 378, and 396 nm, respectively; in solid state, absorptions were at 398, 390, and 442 nm, respectively. The fluorescence emission was at 540, 540 and 604 nm, respectively, the 2-(4-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile showed a red shift in the emission of 64 nm compared to the other two compounds. The fluorescence quantum yield for the compounds in powder form showed values of 0.05, 0.14, and 0.006, respectively; compared with the value measured for the Alq3 reference, 2-(3”-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile had a lightly higher value. The third harmonic generation measurement for 2-(2’-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile yielded a χ(3) value of 5.5 × 10−12 esu, similar to that reported for commercial polymers.

X-Ray Crystal Structures of a 1-(p-fluorophenyl)-2-(α-pyridyl)ethanol Intermediate and the 1-(p-fluorophenyl)-2-(α-pyridyl)ethene Dehydration Compound Obtained from the Condensation Reaction of 2-Methylpyridine and p-Fluorobenzaldehyde

The compound 1-(p-fluorophenyl)-2-(�-pyridyl)ethanol and its corresponding dehydration compound 1-(p- fluorophenyl)-2-(�-pyridyl)ethene were obtained from the Knoevenagel condensation reaction between 2-methylpyridine with p-fluorobenzaldehyde. The X-ray structure determined for 1-(p-fluorophenyl)-2-(�-pyridyl)ethanol reveals that the compound crystallizes in the monoclinic system space group, P21/n, containing four molecules in each crystal unit cell (a = 5.3664(15) A, b = 8.343(2) A, c = 25.056(6) A, and  = 93.837(15)°). The crystal structure shows the formation of an intermolecular hydrogen bond O-H … N between the oxygen atom of the O-H and the nitrogen atom of a pyridine group of the next molecule. The condensation product 1-(p-fluorophenyl)-2-(2-pyridyl)ethene crystallizes in the monoclinic sys- tem, in the Cc space group, with unit cell dimensions a = 22.920(7) A, b = 5.9149(14) A, c = 7.8544(15) A, and  = 104.16(2)°. The molecular structure shows the p-fluorophenyl ring attached to the double bond and located trans to the pyridine ring. The crystallography data give evidence that the intermediary compound is actually the alcohol just before the dehydration process that yields the trans double bond of the 1-(p-fluorophenyl)-2-(� -pyridyl)ethene.

1-( p -Fluorophenyl)-2-(2′-pyridyl)ethanol and 1-( p -fluorophenyl)-2-(2′-pyridyl)ethene obtained from the condensation reaction of 2-picoline and p -fluorophenylaldehyde under catalyst- and solvent-free conditions

The novel intermediate 1-(p-fluorophenyl)-2-(2′-pyridyl)ethanol or 2-[2′-(1-hydroxy-1-(p-fluorophenyl)ethyl]pyridine and the corresponding novel dehydration compound 1-(p-fluorophenyl)-2-(2′-pyridyl)ethene or 2-[p-fluorophenylvinyl]pyridine were obtained from the condensation reaction of p-fluorophenylaldehyde and 2-picoline under catalyst-and solvent-free conditions. The intermediate 1-(p-fluorophenyl)-2-(2′-pyridyl)ethanol was obtained at 42 h reaction time and temperature of 120°C, respectively. 1H-NMR, IR spectroscopic data of the 1-(p-fluorophenyl)-2-(2-pyridyl)ethanol clearly showed the presence of the-CH2-CHOH-group. The compound was obtained as a white powder with m.p. 121–122°C and a yield of 8%. For 1-(p-fluorophenyl)-2-(2-pyridyl)ethene, the reaction conditions were similar, but the reaction temperature was increased to yield the double bond in the 1-(p-fluorophenyl)-2-(2′-pyridyl)ethene. At the reaction temperature of 140°C, the compound was a slightly brown powder with a m.p. of 78°C and yield of 18%. 1H-NMR, IR spectroscopic data for the 1-(p-fluorophenyl)-2-(2′-pyridyl)ethene showed the presence of a double bond in trans configuration (-CH=CH-), characteristic of a styrylpyridine.

X-ray crystal structure of 2-styrylpyridine

We have crystallized the 2-styrylpyridine from the condensation reaction between the 2-methylpyridine with benzaldehyde in the formation of the model compound 2-styrylpyridine. The X-ray structure and NMR are currently reported. The main features of the structure is that is shows a localization of the double bonds rather than a delocalization of π electrons in an aromatic fashion.

Crystal and molecular structure of o-methacryloylaminophenylarsonic acid

AbstractThe title compound, o-methacryloylaminophenylarsonic acid (o-MAPHA), C10H12AsNO4, is a monomer used to obtain water-soluble polyelectrolytes. It was obtained from the condensation reaction of o-arsanilic acid and methacryloyl chloride. Crystallization from aqueous ethanol solution yielded colorless prismatic crystals, and one was used for X-ray analysis. The crystal structure was solved using direct methods with a refined R1 = 0.0483. The crystal structure belongs to the triclinic system, space group