Push-Pull Heterocyclic Dyes Based on Pyrrole and Thiophene: Synthesis and Evaluation of Their Optical, Redox and Photovoltaic Properties

Three heterocyclic dyes were synthesized having in mind the changes in the photovoltaic, optical and redox properties by functionalization of 5-aryl-thieno[3,2-b]thiophene, 5-arylthiophene and bis-methylpyrrolylthiophene π-bridges with different donor, acceptor/anchoring groups. Knoevenagel condensation of the aldehyde precursors with 2-cyanoacetic acid was used to prepare the donor-acceptor functionalized heterocyclic molecules. These organic metal-free dyes are constituted by thieno[3,2-b]thiophene, arylthiophene, bis-methylpyrrolylthiophene, spacers and one or two cyanoacetic acid acceptor groups and different electron donor groups (alkoxyl, and pyrrole electron-rich heterocycle). The evaluation of the redox, optical and photovoltaic properties of these compounds indicate that 5-aryl-thieno[3,2-b]thiophene-based dye functionalized with an ethoxyl electron donor and a cyanoacetic acid electron acceptor group/anchoring moiety displays as sensitizer for DSSCs the best conversion efficiency (2.21%). It is mainly assigned to the higher molar extinction coefficient, long π-conjugation of the heterocyclic system, higher oxidation potential and strong electron donating capacity of the ethoxyl group compared to the pirrolyl moiety.

Quantitative determination of cyanoacetic acid content in teriflunomide drug substance by ion chromatography using conductivity detector

Background The current study focuses on the development and validation of an analytical method for quantifying cyanoacetic acid (CAA) in teriflunomide drug substance using a high-performance ion chromatography (IC) with cation suppressed conductivity detection (TFM). Water was used as the diluent for preparing the sample solution, which was injected into a standard chromatographic device with 250 mm, 4.0 mm ID, and 5.0 μm particle size Metrosep A Supp 5 Ion exchange column and a suppressed conductivity detector. At a flow rate of 0.6 mL min−1 and a temperature of 40 °C, the mobile phase was delivered in an isocratic mode. Results CAA and TFM had retention times of 12.78 and 15.82 min, respectively. CAA has a limit of detection (LOD) of 33 μg/g and a limit of quantification (LOQ) of 101 μg/g, respectively. For LOD and LOQ accuracy, the percentage RSD of CAA is 1.7 and 1.2, respectively. The average CAA recovery percentage was found to be between 98.6 and 100.1%. With a value of 0.9998, the calibration curve yielded an excellent linear correlation coefficient for CAA. According to the ICH guidelines, all verification parameters are within the range, indicating that the system is stable. Conclusion The elution time and run time in the currently developed ion chromatography analytical method have been reduced, demonstrating that the method is cost-effective and generally accepted, as well as simple and functional, and can be used in routine quality control tests in the industry.

Synthesis and structure-property studies of organic dyes possessing unique fused thiophene π-spacers

This thesis examines the synthesis of metal-free organic dyes for light-harvesting applications within the DSSC manifold. All DSSC organic dyes possess a similar donor-π-spacer-acceptor (D-π-A) motif. Here, triphenylamine (TPA) is employed as a donor owing to its redox stability and cyanoacetic acid has been utilized as an acceptor due to its electron-withdrawing ability. Thiophenes are ubiquitous in organic materials chemistry owing to their exceptional charge transport behavior, and in this body of work, π-spacers incorporating benzodithiophene and thiophene-quinones have been incorporated into a DSSC dye and their utility explored. Fused thiophene cores are non-innocent π-spacers. Non-innocent, in this context, is defined as π-spacers that incorporate a secondary chromophore or redox active species (benzodithiophene or quinone).

Synthesis and structure-property studies of organic dyes possessing unique fused thiophene π-spacers

This thesis examines the synthesis of metal-free organic dyes for light-harvesting applications within the DSSC manifold. All DSSC organic dyes possess a similar donor-π-spacer-acceptor (D-π-A) motif. Here, triphenylamine (TPA) is employed as a donor owing to its redox stability and cyanoacetic acid has been utilized as an acceptor due to its electron-withdrawing ability. Thiophenes are ubiquitous in organic materials chemistry owing to their exceptional charge transport behavior, and in this body of work, π-spacers incorporating benzodithiophene and thiophene-quinones have been incorporated into a DSSC dye and their utility explored. Fused thiophene cores are non-innocent π-spacers. Non-innocent, in this context, is defined as π-spacers that incorporate a secondary chromophore or redox active species (benzodithiophene or quinone).

Nickel-Catalyzed Reductive Arylation of Redox Active Esters for the Synthesis of α-Aryl Nitriles – Role of a Chlorosilane Additive

<p>A nickel-catalyzed reductive cross-coupling of redox-active <i>N</i>-hydroxyphthalimide (NHP) esters and iodoarenes for the synthesis of α-aryl nitriles is described. The NHP ester substrate is derived from cyanoacetic acid, which allows for a modular synthesis of substituted α-aryl nitriles, an important scaffold in pharmaceutical sciences. Mechanistic studies reveal that decarboxylation of the NHP ester to the reactive radical intermediate is accomplished by a combination of a chlorosilane additive and Zn dust. The reaction exhibits a broad scope as many functional groups are compatible under the reaction conditions, including complex highly functionalized medicinal agents.</p>

Nickel-Catalyzed Reductive Arylation of Redox Active Esters for the Synthesis of α-Aryl Nitriles – Role of a Chlorosilane Additive

<p>A nickel-catalyzed reductive cross-coupling of redox-active <i>N</i>-hydroxyphthalimide (NHP) esters and iodoarenes for the synthesis of α-aryl nitriles is described. The NHP ester substrate is derived from cyanoacetic acid, which allows for a modular synthesis of substituted α-aryl nitriles, an important scaffold in pharmaceutical sciences. Mechanistic studies reveal that decarboxylation of the NHP ester to the reactive radical intermediate is accomplished by a combination of a chlorosilane additive and Zn dust. The reaction exhibits a broad scope as many functional groups are compatible under the reaction conditions, including complex highly functionalized medicinal agents.</p>

Nickel-Catalyzed Reductive Arylation of Redox Active Esters for the Synthesis of -Aryl Nitriles – Role of a Chlorosilane Additive

<div><p>A nickel-catalyzed reductive cross-coupling of redox-active <i>N</i>-hydroxyphthalimide (NHP) esters and iodoarenes for the synthesis of α-aryl nitriles is described. The NHP ester substrate is derived from cyanoacetic acid, which allows for a modular synthesis of substituted a-aryl nitriles, an important scaffold in pharmaceutical sciences. Mechanistic studies reveal that decarboxylation of the NHP ester to the reactive radical intermediate is accomplished by a combination of a chlorosilane additive and Zn dust. The reaction exhibits a broad scope as many functional groups are compatible under the reaction conditions, including complex highly functionalized medicinal agents.</p></div>

Orthoamide und Iminiumsalze, CI. Umsetzungen von N,N,N′,N′-Tetramethylharnstoffdiethylacetal mit CH2-aciden Verbindungen

N,N,N′,N′-Tetramethylurea diethylacetal reacts with CH2-acidic compounds as benzylcyanide, cyanoacetic acid derivatives malonodinitrile and nitromethane to give ketene aminals or ketene-O,N-acetales. Low polar solvents favour mostly the formation of ketenaminals. The yields of ketenaminals and ketene-O,N-acetals can be improved in some cases by addition of trimethylsilyldimethylamine. The reactions of the urea acetal with diethylmalonate, ore acetyl acetone, stops at the stage of the N,N′,N″-permethylated guanidinium salts with carbanionic counterions. The formation of bis(dimethylamino)methylene-diethylmalonate from the urea acetal and diethylmalonate can be initiated by addition of trimethylsilyldimethylamine/trimethylsilylcyanide. N,N,N′,N′,N″,N″-Hexamethylguanidinium cyanide is formed in the analogous reactions of the urea acetal with N,N-dimethylcyanacetamide or diethylsuccinate. The N,N′,N″-Hexamethyl-guanidinium nitrite can be obtained from the urea acetal and nitropropane.