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Arcos W.A.,University of Valle | Guimaraes R.R.,University of Sao Paulo | Insuasty B.,University of Valle | Insuasty B.,Center for Bioinformatics and Photonics io | And 3 more authors.
Journal of Molecular Structure | Year: 2016

The push-pull behavior of novel dyes, based on vinazene electron-acceptor groups linked to arrays of triphenylamine (TPA) electron-donor group, was studied by electronic absorption and emission spectroscopy, as well as by cyclic voltammetry. The most stable ground state structure and their electronic properties were modeled by density functional theory (DFT) calculations using the B3LYP functional and 6-31G++ basis set, whereas the electronic properties in the excited states were calculated by TD-DFT, under the same functional and basis set, using SCF and PCM methods. The theoretical calculations matched well with experimental data, showing that λmax of the lowest energy absorption band can be assigned to an intramolecular charge transfer transition. In fact, the HOMO and LUMO are respectively localized on the TPA donor and the dicyanomethylene acceptor moiety confirming a remarkable push-pull character. Photoelectrochemical cells parameters were correlated with dyes structural properties showing to be consistent with the anchoring through the nitrogen atoms of CN groups. The nature of the donor-acceptor groups, conformation and number of anchoring CN groups (2 seems to be the best) strongly influenced the overall efficiency of dye sensitized solar cells. © 2016 Elsevier B.V. All rights reserved. Source


Quiroga J.,University of Valle | Quiroga J.,Center for Bioinformatics and Photonics io | Romo P.E.,University of Valle | Romo P.E.,Center for Bioinformatics and Photonics io | And 9 more authors.
Journal of Molecular Structure | Year: 2016

The synthesis of 5-aryl-4-oxo-3,4,5,8-tetrahydropyrido[2,3-d]pyrimidine-7-carboxylic acids 3 from the reaction of 6-aminopyrimidines 1 with arylidene derivatives of pyruvic acid 2 under microwave and ultrasound irradiation is described. The orientation of cyclization process was determined by NMR measurements. The methodology provides advantages such as high yields and friendly to the environment without the use of solvents. The antioxidant properties, DPPH free radical scavenging, ORAC, and anodic potential oxidation of the new pyridopyrimidines were studied. © 2016 Elsevier B.V. Source


Quiroga J.,University of Valle | Quiroga J.,Center for Bioinformatics and Photonics io | Acosta P.,University of Valle | Acosta P.,Center for Bioinformatics and Photonics io | And 6 more authors.
Journal of Molecular Structure | Year: 2015

New pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidin-5(6H)-one derivatives 5 were prepared by cyclocondensation reaction between heterocyclic o-aminonitriles 3 and carboxylic acids 4 in the presence of sulfuric acid as catalyst. This procedure provides the desired compound in good yield with a simple one-step methodology. The obtained products show interesting fluorescence properties in both solution and solid state; in this way several spectra of absorption and emission were measured for selected compounds 5b, 5e, 5g and 5j, showing a broad and intense emission band around of 470 nm. In other to understand the electronic transition processes, theoretical calculations were performed at TD-DFT level, using B3LYP as functional and 6-31(d,p) as basis set, finding a good agreement with experimental measurements. © 2015 Elsevier B.V. All rights reserved. Source

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