Poly(2-aminobenzoic acid) and poly(3-aminobenzoic acid) were synthesized by chemical polymerization of the respective monomers with aqueous 1M hydrochloric acid and 0.49M sodium hydroxide, using ammonium persulfate as an oxidizing agent. In addition, polymerization in an acid medium was carried out in the presence of metal ions, such as Cu(II), Ni(II), and Co(II). Poly(2-aminobenzoic acid-co-aniline) and poly(3-aminobenzoic acid-co-aniline) were synthesized by chemical copolymerization of aniline with 2-and 3-aminobenzoic acids, respectively, in aqueous 1M hydrochloric acid. The copolymers were synthesized at several mole fractions of aniline in the feed and characterized by UV-visible and FTIR spectroscopy, the thermal stability, and the electrical conductivity. Metal ions, such as Cu(II), Ni(II), and Co(II), were incorporated into homo-and copolymers by the batch method. The percentage of metal ions in the polymers was higher in the copolymers than in the homopolymers. The thermal stability of the copolymers increased as the feed mole fraction of aniline decreased and varied with the incorporation of metal ions in the polymers. The electrical conductivity of the homo-and copolymers was measured, which ranged between 10 Ϫ3 and 10 Ϫ10 S cm Ϫ1 .

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Several poly(thiophene) derivatives containing p-phenylenevinylene (PV) as an electron-donor were synthesized using FeCl 3 . PV units are regularly spaced in two, four and eight thiophenyl units across the main chain. PV units and the gradual increase in the number of thiophene units affect the properties of polymers such as poly(3-hexylthiophene), (P3HT). Polymers, labeled as poly(FV1Th), poly(FVBiTh) and poly(FVTeTh) were characterized by FT-IR and UV-Vis spectrometry, elemental analysis, thermal stability (TGA), differential scanning calorimetry (DSC) and cyclic voltammetry (CV). Conjugation increases with increasing thiophene rings in the main chain and the conjugation is higher in polymers that exhibited different optical absorption, effective conjugation, similar intrinsic viscosity, and high thermal stability with a weight loss less than 10% at decomposition temperatures higher than 300 1C (except poly(FVTeTh). DSC showed melting points over 200 1C and the formation of crystalline zones was found in all cases. An increase in the number of thiophene rings in the main chain resulted in a more ordered crystalline molecular structure. Moreover, the polymers presented redox processes at a potential lower than that of P3HT. The Highest Occupied Molecular Orbital (HOMO), Lowest Unoccupied Molecular Orbital (LUMO) and optical band gap (E g ) were measured and the values obtained were compared with those of P3HT. The effect caused by PV units and the increase of thiophenyl units in the chains on HOMO, LUMO, band gap, fusion, crystallinity and TGA is reported. The E g of the monomers was greater than that of P3HT. The results showed that with respect to P3HT, polymers HOMO and LUMO are lower and in some cases by a slight change in E g . The PV effect as an electron donor causes a decrease in the HOMO and LUMO, envisaging them as potential polymers to be studied in organic photocells.

-pyrazoles may be obtained by reaction of 3-[2-(R 1 -phenyl)hydrazono)]pentane-2,4-dione with H 2 NOH·HCl and R 2 -4-C 6 H 4 -NHNH 2 , respectively. The reactions were performed in ethanol as solvent and catalyzed by glacial acetic acid.

Key indicatorsSingle-crystal X-ray study T = 298 K Mean (C-C) = 0.004 Å R factor = 0.043 wR factor = 0.074 Data-to-parameter ratio = 9.5For details of how these key indicators were automatically derived from the article, seeMolecules of the title compound, C 12 H 11 N 3 O 3 , are linked into zigzag chains by O-HÁ Á ÁN hydrogen bonds. The crystal structure is further stabilized bystacking interactions.

Polytriphenylamine (PTPA), a Schiff base polymer containing triphenylamine (TPA) segments and whose monomer contains triphenylamine and thiophene end groups, was synthesized. The monomer structure enabled the polymerization to be performed under conditions similar to those of thiophene. Oxidative coupling using FeCl 3 as oxidizing agent in anhydrous CHCl 3 medium was employed for the polymer synthesis. Scanning electron microscopy, fluorescence spectroscopy, and cyclic voltammetry were used to characterize the polymer. PTPA exhibited high thermal stability with a mass loss of 13.3 % at 546.5 °C. The fluorescence spectrum showed emission at 300-550 nm and the optical band gap was found to be 2.6 eV. It was also established that PTPA forms complexes with Lewis acids, e.g. MoO 3 and CuI. Its absorption band widened and extended up to the near-IR. It was seen that PTPA is rich in π-electrons and thus can act as electron donor. The value of the Highest Occupied Molecular Orbital (HOMO) was −5.35 eV indicating its potential application in optoelectronic devices. An attempt was also made to investigate the photovoltaic potential of PTPA. Organic photovoltaic devices with various buffer layer structures, namely ITO/CuI/PTPA/C 60 /BCP/Al, ITO/MoO 3 /PTPA/C 60 /BCP/Al, and ITO/MoO 3 /CuI/PTPA/C 60 /BCP/Al, where ITO stands for indium tin oxide and BCP for bathocuproine, were utilized for the studies. Power conversion efficiency of these devices ranged between 0.21 and 0.43% under simulated AM 1.5 illumination (100 mW cm −2 ). This result proved that polymers containing TPA in the main chain hold promising properties that would allow their use in photovoltaic devices.