Alejandro Ortiz

Vinyl spacers—tuning electron transfer through fluorene-based molecular wires

Rigid and soluble electron donor–acceptor conjugates (3 and 11) that combine π-extended tetrathiafulvalene (exTTF) as an electron donor and C60 as an electron acceptor have been synthesized using oligo-vinylfluorene (oFV) linkers to connect the electroactive entities. Fluorescence and transient absorption measurements confirm that light-induced excitation induces charge-transfer reactions over distances of 28 A in THF. The incorporation of vinylene spacers into oligofluorene molecular wires has been shown both experimentally and theoretically to improve the charge-transfer features significantly to give a β value of 0.075 ± 0.001 A−1. Enhanced π-conjugation caused by higher orbital overlap is responsible for this trend.

Microwave induced three-component synthesis and antimycobacterial activity of benzopyrazolo[3,4-b]quinolindiones.

Three series of novel 4-arylbenzo[h]pyrazolo[3,4-b]quinolin-5,6-diones 4, 7 and 9 have been efficiently obtained in good yields by three-component microwave assisted reaction between aminopyrazoles 1 or 6 (both 1-phenyl and 1-H substituted), 2-hydroxynaphthoquinone 2 and benzaldehydes 3. Compounds 4, 7 and 9 have been evaluated against fifteen Mycobacterium spp strains, and six of them have shown antimycobacterial activity. The highest inhibitory activity with MIC ≤2 μg/mL for three of these compounds (4a, 4b and 4g) was related with their highest lipophilicity and lesser polarity within these series.

Microwave-assisted synthesis under solvent-free conditions of (E)-2-(Benzo[d]thiazol-2-yl)-3-arylacrylonitriles

Uma serie de (E)-2-(benzo[d]tiazol-2-il)-3-arilacrilonitrilas foi sintetizada pela condensacao de Knoevenagel assistida por microondas, na ausencia de solvente, partindo do correspondente 2-(benzo[d]tiazo-2-il)acetonitrila e aldeidos aromaticos, contendo tanto grupos doadores de eletrons, como retiradores. Os tempos de reacao foram consideravelmente curtos e os produtos, obtidos em rendimentos moderados (50-75%) e boa pureza. A configuracao da dupla ligacao da acrilonitrila nao pode ser estabelecida por metodos comuns de RMN. No entanto, estudos teoricos sugerem que nesses compostos o isomero E e mais estavel do que o Z, o que esta de acordo com algumas evidencias experimentais. A series of (E)-2-(benzo[d]thiazol-2-yl)-3-arylacrylonitriles was synthesized by microwave assisted Knoevenagel condensation under solvent-free conditions from the corresponding 2-(benzo[d]thiazol-2-yl)acetonitrile and aromatic aldehydes with electrondonating/electronwithdrawing groups. The reaction times were considerably short and the products obtained in moderate yields (50 to 75%) and good purity. The configuration of the acrylonitrile double bond could not be established by regular NMR methods. However, theoretical studies suggest that the E isomer is more stable than Z, which is in good agreement with some experimental evidences.

New organic dyes with high IPCE values containing two triphenylamine units as co-donors for efficient dye-sensitized solar cells

Here we report the synthetic routes as well as the structural and electronic properties of five new triphenylamine-based organic dyes and their application in dye-sensitized solar cells. In the designed dyes, two triphenylamine groups act as the electron donor units and the electron acceptor is a cyanoacrylic acid, and these units are linked by different π-conjugated spacers including thiophene, dioctylfluorene, ethylcarbazole, and benzo-dithiophene. Density functional theory was employed to study the electron distribution and the intramolecular charge transfer (HOMO–LUMO) of the dyes. Extending the π-conjugation of the dyes broaden and red-shift the bands and improves the light-harvesting ability, however, a device made with triphenylamine maximizer-based dye TPAM-1 without a π-conjugated spacer exhibited the best photovoltaic performance with a short-circuit photocurrent density (Jsc) of 11.37 mA cm−2, an open-circuit voltage (Voc) of 0.836 V, and a fill factor (FF) of 0.603, corresponding to an overall power conversion efficiency of 5.67% under AM 1.5 irradiation (100 mW cm−2).

Microwave-Assisted Synthesis of Novel Pyrazolo[3,4-g][1,8]naphthyridin-5-amine with Potential Antifungal and Antitumor Activity.

The microwave assisted reaction between heterocyclic o-aminonitriles 1 and cyclic ketones 2 catalyzed by zinc chloride led to new series of pyrazolo[3,4-b][1,8]naphthyridin-5-amines 3 in good yields. This procedure provides several advantages such as being environmentally friendly, high yields, simple work-up procedure, broad scope of applicability and the protocol provides an alternative for the synthesis of pyrazolonaphthyridines. The whole series showed antifungal activities against Candida albicans and Cryptococcus neoformans standardized strains, being compounds with a 4-p-tolyl substituent of the naphthyridin scheleton (3a, 3d and 3g), the most active ones mainly against C. albicans, which appear to be related to their comparative hydrophobicity. Among them, 3d, containing a cyclohexyl fused ring, showed the best activity. The anti-Candida activity was corroborated by testing the three most active compounds against clinical isolates of albicans and non-albicans Candida strains. These compounds were also screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines. Compounds 3a and 3e showed remarkable antitumor activity against cancer cell lines, with the most important GI50 values ranging from 0.62 to 2.18 μM.

A straightforward and efficient method for the synthesis of diversely substituted β-aminoketones and γ-aminoalcohols from 3-(N,N-dimethylamino)propiophenones as starting materials

Bibliotecas de novos β-aminocetonas e γ-aminoalcoois que mostram uma grande diversidade estrutural foram facilmente obtidas a partir de uma abordagem simple, utilizando os derivados da 3-(N,N-dimetilamino)propiofenona como material de partida chave. O procedimento envolveu inicialmente a N-alquilacao de benzilaminas secundarias com derivados de propiofenona produzindo as desejadas β-aminocetonas. A reducao quimica ou catalitica dos grupos carbonilo atinge a obtencao dos γ-aminoalcoois em bons rendimentos. Este protocolo mostrou ser uma via alternativa conveniente para a sintese do anestesico local Falicain® e para a droga topica antifungica Naftifina®.

Free-base tetraarylporphyrin covalently linked to [60]fullerene through ethynylfluorene spacer

The synthesis, structural and electronic characterization of novel electroactive systems based on porphyrin-fullerene in which the chromophores are linked by an ethynylfluorene spacer unit is reported. Sonogashira couplings have been used in short and efficient sequences to give access to these new molecules on a practical scale. The absorption studies, voltamperometric measurements and theoretical calculations at DFT level reveal the push-pull behavior for these systems.

Geometric Influence on Intramolecular Photoinduced Electron Transfer in Platinum(II) Acetylide-Linked Donor-Acceptor Assemblies

A new donor-acceptor system, in which the electron donor triphenylamine (TPA) and the electron acceptor C60 are bridged through a cis- or trans-platinum(II) acetylide spacer have been prepared. Ground-state studies were conducted using electrochemistry and UV/Vis spectroscopy. Fluorescence studies suggested that charge transfer is the deactivation mechanism for the singlet excited state, and this was verified by transient absorption spectroscopy. Selective photoexcitation of 1 and 2 at 387 nm leads to a fast charge transfer between the TPA and C60, which gives rise to a radical ion-pair state (TPA(·+)-Pt-C60(·-)). Our results suggest that charge transfer is favored for the cis configuration while the presence of the trans configuration in the Pt(II) diacetylide results in a longer-lived charge separated states.

Antimycobacterial Activity of Pyrimido[4,5‐b]diazepine Derivatives

Three series of novel 8,9‐dihydro‐7H‐pyrimido[5,4‐b][1,4]diazepines, 4a–d, 5a–d, and 7a–d, were efficiently obtained in good yields using simple reaction methodologies. These pyrimidodiazepines were evaluated against 15 Mycobacterium spp. strains. Moderate activity in the inhibition of 13 microorganisms was obtained for the four compounds 4a, 5a, 5c, and 5d.

Optical and Electronic Properties of Molecular Systems Derived from Rhodanine

Push-pull functional compounds consisting of dicyanorhodanine derivatives have attracted a lot of interest because their optical, electronic, and charge transport properties make them useful as building blocks for organic photovoltaic implementations. The analysis of the frontier molecular orbitals shows that the vertical transitions of electronic absorption are characterized as intramolecular charge transfer; furthermore, we show that the analyzed compounds exhibit bathochromic displacements when comparing the presence (or absence) of solvent as an interacting medium. In comparison with materials defined by their energy of reorganization of electrons (holes) as electron (hole) transporters, we find a transport hierarchy whereby the molecule ( Z)-2-(1,1-dicyanomethylene)-5-[(4-dimethylamino)benzylidene]-1,3-thiazol-4 is better at transporting holes than molecule ( Z)-2-(1,1-dicyanomethylene)-5-(tetrathiafulvalene-2-ylidene)-1,3-thiazol-4.