Covalently linked thieno[2,3-b]thiophene-fullerene dimers: synthesis and physical characterization.

Thienothiophene (TT) has received great attention in the fields of electronics and optoelectronics. Here we report a synthesis and characterization of fullerene-donor-fullerene triads linked to thieno[2,3-b]thiophene as a donor. The photophysical and electrochemical properties of the new dumbbells were investigated using UV-vis spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and square wave voltammetry. The results showed that both compounds have higher LUMO energy levels than PC61BM, indicating that they can be used in photovoltaic applications. Furthermore, the powder was structurally and morphologically characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The SEM revealed the morphological characterization of the two derivatives as globular and urchin-like supramolecular assemblies.

Correction: Microwave-assisted chemoselective synthesis and photophysical properties of 2-arylazo-biphenyl-4-carboxamides from hydrazonals.

[This corrects the article DOI: 10.1039/D3RA04558G.].

Microwave-assisted chemoselective synthesis and photophysical properties of 2-arylazo-biphenyl-4-carboxamides from hydrazonals.

The reaction of 3-oxo-2-arylhydrazonopropanals with acetoacetanilide in an equimolar ratio, under DBU/1,4-dioxane/microwave irradiation reaction conditions, resulted in chemoselective formation of 4-arylazo-5-hydroxy-benzamide derivatives. The structures of the obtained biphenyl-4-carboxamides were characterized by several spectroscopic techniques including IR, 1H- and 13C-NMR, MS and HRMS, and X-ray single crystals of three examples. The photophysical properties of the new products were also evaluated, with a particular focus on their absorption and emission spectra, which provided valuable information regarding their optical properties. The new compounds emitted 513-549 nm green fluorescence in acetone solution under UV irradiation.

Efficient and Recyclable Solid-Supported Pd(II) Catalyst for Microwave-Assisted Suzuki Cross-Coupling in Aqueous Medium.

Solid-supported catalysts play efficient and crucial roles in organic synthesis. A solid-supported palladium(II) complex based on chitosan was synthesized and fully characterized using all possible tools (Fourier transform infrared spectroscopy, thermogravimetry analysis, differential scanning calorimetry, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectrometry, scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller analysis). The catalytic activity of the solid-phase catalyst in Suzuki cross-coupling reactions was evaluated in aqueous solvents under both conventional heating and microwave irradiation conditions. The recyclability and thermal stability of the prepared catalyst were also examined, and the catalyst was found to be active till five consecutive runs without a notable loss of activity under the microwave condition, with the turnover number and turnover frequency values reaching 19,019 and 114,114 h-1, respectively.

Synthesis and Electrochemistry of Novel Dumbbell-Shaped Bis-pyrazolino[60]fullerene Derivatives Formed Using Microwave Radiation.

The design of covalently linked [60]fullerene dimers has gained increased attention, as the linked electron donors or acceptors are in close proximity to the surface of the C60, providing a valuable approach to novel molecular electronic devices. Herein, new compounds involving C60 dumbbells covalently connected by the π-conjugated system from azobenzene and diaryl ether linkers were synthesized following the bifunctional cycloaddition reactions to C60 using microwave radiation. The structural identity of the fullerene dimers has been determined using spectroscopic techniques including Fourier transform infrared (FT-IR), matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF), and NMR spectroscopy, and the photophysical and the electrochemical properties for the new dumbbells have been examined using UV-vis spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and square wave voltammetry. Both new dimers show electronic interaction with the fullerene cage and higher electron affinity than the pristine C60.

Synthesis and Electrochemistry of New Furylpyrazolino[60]fullerene Derivatives by Efficient Microwave Radiation.

Efficient one-pot synthesis of new series of furylpyrazolino[60]fullerene derivatives was prepared by [3 + 2] cycloaddition reaction mediated with (diacetoxyiodo)benzene (PhI(OAc)2) as an oxidant in o-dichlorobenzene (ODCB) under microwave irradiation. Different techniques have been used to confirm the structural identity including FT-IR, fast atom bombardment (FAB)-mass, NMR, and single-crystal X-ray diffraction, in addition to investigating the photophysical properties and the electrochemical properties for the new compounds using UV-Vis spectra, fluorescence spectra, cyclic voltammetry, and square wave voltammetry. Three of these pyrazolino[60]fullerene compounds showed better electron affinity than the parent C60 in the ground state.

Facile Assembling of Novel 2,3,6,7,9-pentaazabicyclo- [3.3.1]nona-3,7-diene Derivatives under Microwave and Ultrasound Platforms.

Reactions of a series of 3-oxo-2-arylhydrazonopropanal derivatives with two molar ratio of ammonium acetate afforded a library of tetrasubstituted 2,3,6,7,9-pentaazabicyclo[3.3.1]nona- 3,7-diene derivatives in good to excellent isolated yields. The reaction was activated with triethylamine catalyst under three different heating modes: thermal, ultrasonic and microwave irradiating conditions in ethanol solvent. The structures of the isolated products were fully characterized by spectral and analytical data as well as X-ray single crystal of selected examples.

Tandem one-pot synthesis of 2-arylcinnolin-6-one derivatives from arylhydrazonopropanals and acetoacetanilides using sustainable ultrasound and microwave platforms.

Several 2-arylcinnolin-6(2H)-one derivatives were synthesized via tandem annulation of a large number of 3-oxo-2-arylhydrazonopropanals with acetoacetanilide under three different heating modes (conventional heating, ultrasound and microwave irradiation) using triethylamine in ethanol. The factors affecting the optimization of the annulation process were thoroughly studied. The annulated structures were established on the basis of 1H and 13C NMR and MALDI-TOF/MS spectral data as well as single crystal X-ray analysis.

Chitosan based heterogeneous catalyses: chitosan-grafted-poly(4-vinylpyridne) as an efficient catalyst for Michael additions and alkylpyridazinyl carbonitrile oxidation.

Chitosan-grafted-poly(4-vinylpyridine) (Cs-PVP) copolymers could be synthesized under heterogeneous conditions in presence of a potassium persulfate and sodium sulfite redox system. The synthesized graft copolymer could be utilized effectively, in the form of beads, as an efficient catalyst for Michael additions of active methylenes to functionally substituted alkenes. Moreover, methyl moiety oxidation in methyl pyridazinyl carbonitriles by H2O2 in the presence of chitosan-g-polyvinyl pyridine-supported iron (III) complex, Cs-PVP/Fe, could be affected. A variety of pyrans, naphthopyrans, and thiopyrans could be synthesized efficiently in the presence of these graft copolymer beads by novel catalytic routes. These polymeric catalysts could be used instead of the old toxic commercial organic basic catalysts, piperidine or pyridine, and could be readily isolated from the reaction mixture and recycled several times without significant loss of catalytic activity.

Studies on 2-arylhydrazononitriles: synthesis of 3-aryl-2-arylhydrazopropanenitriles and their utility as precursors to 2-substituted indoles, 2-substituted-1,2,3-triazoles, and 1-substituted pyrazolo[4,3-d]pyrimidines.

Coupling of 2-benzylmalononitrile with aromatic diazonium salts afforded 3-phenyl-2-arylhydrazonopropanenitriles 4a,b, which were rearranged into 2-cyanoindoles 5a,b upon heating with ZnCl(2) in the presence of glacial acetic acid. The produced indole derivatives 5a,b can be successfully used as valuable precursors to synthesize 1,2,4-oxadiazolylindoles 8a,b. The reaction of arylhydrazononitriles 4a,b with hydroxylamine afforded an amidoximes 9a,b that could be cyclized into 1,2,3-triazole-4-amines 10a,b. In addition, 4a,b could be converted into 4-aminopyrazoles 12a,b via condensation with chloroacetonitrile in the presence of triethylamine as a basic catalyst. Finally, compounds 12a,b were refluxed with dimethylformamide dimethylacetal (DMFDMA) to afford amidines 13a,b that were readily cyclized to the corresponding pyrazolo[4,3-d]pyrimidines 14a,b when refluxed with ammonium acetate.

Studies on 3-oxoalkanenitriles: novel rearrangement reactions observed in studies of the chemistry of 3-heteroaroyl-3-oxoalkanenitriles as novel routes to 2-dialkylaminopyridines.

3-Aroyl and 3-heteroaroyl substituted 3-oxoalkanenitriles were synthesized by the reactions of activated aromatic and hetero-aromatic substances with cyanoacetic acid in the presence of acetic anhydride. As part of studies focusing on the preparation of cyanoacetyl-1-N-methylbenzimidazole, we observed that reaction of N-methyl-benzimidazole with the cyanoanhydride formed by condensation of cyanoacetic acid with acetic anhydride, leads to the formation of 2-(1,3-diacetyl-2,3-dihydro-1H-benzo[d]-imidazol-2-yl)acetonitrile (5), whose structure was confirmed by X-ray crystallographic analysis. 3-Oxoalkanenitriles 3a,b were observed to undergo condensation reactions with dimethylformamide dimethyl acetal (DMFDMA) to afford the corresponding enamino-nitriles, which react with malononitrile to give 2-dialkylaminopyridines through a pathway involving a new, unexpected rearrangement process. Reactions of 3-oxoalkanenitriles with ethyl acetoacetate were found to afford 2-oxopyran-3-carbonitriles, also occurring via this unexpected rearrangement process. Mechanisms to account for both rearrangement reactions are suggested. In addition, reactions of 3-oxoalkanenitriles with acetylacetone in acetic acid in the presence of ammonium acetate result in the formation of pyridine-3-carbonitriles. Finally, upon heating in the presence of zeolite 3-oxoalkanenitriles 3b,c self-trimerized to produce the corresponding aniline derivatives 23b,c.

Green one pot solvent-free synthesis of pyrano[2,3-c]-pyrazoles and pyrazolo[1,5-a]pyrimidines.

Pyrano[2,3-c]pyrazoles are obtained via mixing ethyl acetoacetate, hydrazine hydrate, aldehydes or ketones and malononitrile in the absence of solvent. These same products were also obtained by reacting arylidenemalononitriles 3 with 3-methyl-2-pyrazolin-5-ones. NOE difference experiments confirmed that these products exist solely in the 2H form. Similar treatments of 3-amino-2-pyrazolin-5-one with arylidene-malononitrile afforded adduct 6. Similarly mixing ethyl cyanoacetate, hydrazine hydrate, aldehydes, with malononitrile gave the same product 6. A novel synthesis of 4-oxo-4H-pyrano[2,3-c]pyrazole (8) could be achieved via reacting 3-methyl-2-pyrazolin-5-one with a mixture of cyanoacetic acid and acetic anhydride. Similar treatment of 3-aminopyrazole 11 with the benzylidene-malononitrile produced the pyrazolo[2,3-a]pyrimidines 12a,b.

Studies with beta-oxoalkanonitriles: simple novel synthesis of 3-[2,6-diaryl-4- pyridyl]-3-oxopropanenitriles.

Heteroaromatization of ethyl 2-cyano-4-oxo-2-(2-oxo-2-arylethyl)-4-arylbutanoates 3a,b with ammonium acetate gave ethyl 2,6-diarylisonicotinates 4a,b. Treatment of the latter with acetonitrile afforded novel beta-oxoalkanonitriles 6a,b. Reactions of 6a,b with phenyl hydrazine and hydroxylamine gave the corresponding pyridyl aminopyrazoles 8a,b and pyridyl aminoisoxazoles 10a,b, respectively.

A study on electron impact mass spectrometry of epoxy methylated fullerenols.

Mass spectra of the epoxy methylated[60]fullerenols were obtained by EI mass spectrometry using "desorption" or "in-beam" technique. The mass spectra have an intense molecular monocation peak M(+) and a weak dication peak M(++), revealing the stability of these products under the MS (EI) conditions. The remaining peaks correspond to the successive loss of methyl groups and oxygen atoms for which the pure fullerene represents a more stable product. The distinction between the multiply charged fullerene C(60)(z+) and their fragments with equal m/z was also studied.