Absorption and fluorescence of soluble polar diketo-pyrrolo-pyrroles

Six soluble derivatives of 3,6-diphenyl-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione N-alkylated on pyrrolinone ring with polar substituents in para positions of pendant phenyl rings were synthesized; five of them are reported for the first time. Absorption and fluorescence spectra were studied in solvents of different polarity. The compounds show small solvatochromism of absorption and a moderate positive solvatochromism of fluorescence, especially when substituted by strong electron-donating piperidino substituent. A significant decrease of fluorescence quantum yields and its biexponential decay for dipolar derivatives in polar solvents was tentatively ascribed to the formation of twisted intramolecular charge transfer (TICT) excited state. All six compounds show fluorescence in polycrystalline solid-state with the maxima covering a range over 200 nm in visible and near infrared region.     

Absorption and fluorescence of soluble polar diketo-pyrrolo-pyrroles

Six soluble derivatives of 3,6-diphenyl-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione N-alkylated on pyrrolinone ring with polar substituents in para positions of pendant phenyl rings were synthesized; five of them are reported for the first time. Absorption and fluorescence spectra were studied in solvents of different polarity. The compounds show small solvatochromism of absorption and a moderate positive solvatochromism of fluorescence, especially when substituted by strong electron-donating piperidino substituent. A significant decrease of fluorescence quantum yields and its biexponential decay for dipolar derivatives in polar solvents was tentatively ascribed to the formation of twisted intramolecular charge transfer (TICT) excited state. All six compounds show fluorescence in polycrystalline solid-state with the maxima covering a range over 200 nm in visible and near infrared region.     

The synthesis,characterization, and structure of a series of 4H-thieno[3,4-c]pyrroles and their corresponding pyrrolium cyanoborohydride salts

A general, convenient route toward N-substituted 5,6-dihydro-4H-thieno[3,4-c]pyrroles was accomplished by the reductive amination of 2,5-dimethylthiophene-3,4-dicarbaldehyde with various primary amines in a solution of sodium cyanoborohydride and methanol/acetic acid (80–88% yield). For the N-alkyl cases, the product isolated was the cyanoborohydride salt of the desired product, 1,3-dimethyl-5-alkyl-5,6-dihydro-4H-thieno[3,4-c]-5-pyrrolium cyanoborohydride. For the aryl case employing aniline, the desired free pyrrole, 1,3-dimethyl-5-phenyl-5,6-dihydro-4H-thieno[3,4-c]pyrrole, was isolated. X-ray crystallographic analysis of both the N-propyl and N-phenyl trials confirmed the salt and free amine nature of the products.     

Purple red and luminescent polyiminoarylenes containing the 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP) chromophore

New DPP-containing polyiminoarylenes were prepared from 1,4-diketo-2,5-dihexyl-3,6-di(4′-bromophenyl)pyrrolo[3,4-c]pyrrole and various arylamine derivatives using palladium-catalyzed amination reactions. The arylamine comonomers were aniline (ANI), t-butylaniline (TBA), 2-aminoanthracene (AAN), 1-aminopyrene (APY) and N,N′-diphenyl-p-phenylenediamine (PDA). Purple red polymers with good solubility in common organic solvents and molecular weights between 4.4 and 35.8 kDa were obtained. Polymer solutions were readily fluorescent with quantum yields between 19 and 62%, while solution-cast films only showed a weak fluorescence. All polymers exhibit low band gaps of approximately 1.9 eV. Cyclovoltammetric studies indicate quasireversible oxidation for polymers with TBA, APY and PDA as comonomer units, and quasireversible reduction for the polymer with AAN comonomer unit. Polymers with APY and PDA comonomer units are electrochromic and can be switched between red in the neutral and greenish grey in the oxidized state.     

Intermediates and dyes for synthetic-polymer fibres. Benzo [b]naphtho [3,2-d]thiophene-6,7-dicarboxylic acid imides and benzimidazo dibenzothio

Benzo[b]naphtho[2,3-d]thiophene-6,7-dicarboxylic anhydride (I) is obtained y Pschorr intramolecular cyclisation of 2-(2-aminophenylthio)-1,8-naphthalic anhydride. Condensation with alkylamines and arylamines gives the corresponding imides, which colour synthetic-polymer fibres in greenish-yellow hues, and reaction with o-phenylenediamines affords the isomer mixtures of derivatives of benzimidazo[1,2-b]-dibenzothiopheno-[4,3,2-d,e] isoquinolin-10-one and of benzimidazo-[2,1-a] dibenzothiopheno-[4,3,2-d,e]isoqumolin-10-one, which dye polyester fibres bright reddish-orange. Both series of dyes have excellent fastness to light and sublimation. The colour of the dyes is discussed in relation to the isomeric compounds derived from benzo[k,1]thioxanthene-3,4-dicarboxylic anhydride (III) and from benzo[d]naphtho[1,2-b]thiophene-9,10-dicarboxylic anhydride (II). The synthesis of the individual isomers resulting from reaction of I with o-phenylenediamine is reported and their absorption maxima related to polar factors operative within each isomer.     

Tuning of the neutral state color of the π-conjugated donor-acceptor-donor type polymer from blue to green via changing the donor strength on the polymer

Two donor-acceptor-donor types of π-conjugated monomers were synthesized using Stille coupling reaction. Both monomers were found to produce electroactive polymers upon electrochemical oxidation. The effects of different donor substituents on the polymers' electrochemical and spectroelectrochemical properties were examined. Optical characterization revealed that the band gaps of poly(2-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-3-(2,3-dihydrobenzo[b][1,4]dioxin-7-yl)-5,8-di(thiophen-2-yl)quinoxaline) (PDBQTh) and poly(2-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-3-(2,3-dihydrobenzo[b][1,4]dioxin-7-yl)-5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-8-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)quinoxaline) (PDBQEd) were 1.5 eV and 1.3 eV, respectively. PDBQEd reveals two distinct absorption bands as expected for this type of donor-acceptor-donor polymer at 423 and 738 nm, while PDBQTh has a single absorption band at 630 nm. The colorimetry analysis revealed that while PDBQTh has a blue color, PDBQEd showed a green color in the neutral state. PDBQEd revealed reversible n-doping.     

Poly(p-phenylene vinylene) derivatives with ester- and carboxy-functionalized substituents: a versatile platform towards polar functionalized conjugated polymers

A polar functionalized poly(p-phenylene vinylene) (PPV) derivative, ester containing poly(1,4-(2-(pentyloxy-5-carboxy methylester)-5-methoxyphenylene)vinylene), has been prepared via the sulfinyl precursor route. Subsequently, the carboxylic acid containing poly(1,4-(2-(5-carboxypentyloxy)-5-methoxyphenylene)vinylene) is readily obtained by the basic hydrolysis of the ester side groups. This carboxylic acid substituted polymer exhibits significantly improved optical properties as compared to previously reported similar polymers. To obtain polar functionalized PPV derivatives with more complex tailored substituents a versatile novel approach is presented based on the Mitsunobu reaction conditions via a post-polymerization functionalization of the carboxylic acid side groups. Using these reaction conditions substituents containing various ester groups, i.e. 4-nitrobenzyl, 2-nitrobenzyl, 5-(methyl)furfural and 3-N,N-dimethylamino-1-propane, have been covalently attached to the phenylene ring. Analytical data of the functionalized polymers are consistent with a quantitative functional group substitution. The results demonstrate that the employed functionalization method allows for the introduction of a large variety of polar substituents in a straightforward manner.     

Facile selective synthesis of new furo[3,4-d]-1,3-thiazoles

In presence of triethylamine, the reaction of substituted 2-aroyl-hydrazinecarbothioamides with 1,4-Diphenyl-but-2-yne-1,4-dione afforded novel furo[3,4-d]-1,3-thiazoles in good yield. The reaction mechanism suggests that the second molecule of 1,4-Diphenyl-but-2-yne-1,4-dione behaved as an oxidizing agent.     

Synthesis and characterization of Cu(I) and Zn(II) complexes with new sulfur-bearing isoxazole- or pyrazole-based ligands

The synthesis of the new ligands 6-(5-methyl-1,2-oxazol-3-yl)-2,3-dihydro-5H-[1,4] dithiino[2,3-c]pyrrole-5,7(6H)-dione (isox′) and 6-(3-methyl-1H-pyrazol-5-yl)-2,3-dihydro-5H-[1,4]dithiino[2,3-c]pyrrole-5,7(6H)-dione (pyraz′) and their coordination chemistry toward Cu(I) and Zn(II), was studied. The ligands and their complexes were characterized using a combination of either multinuclear NMR (¹H and ¹³C{¹H}), HRMS, FTIR or Uv–Vis spectroscopy. The solid state structures of ligand isox′ and complexes [Cu(pyraz′)₂]OTf and [Zn(OOCCF₃)₂(pyraz′)₂] were determined. Interestingly, isox′ presents a yellow luminescence in its free form. Additionally, the ability of isox′ to coordinate as an N–O bidentate ligand or as an N–S bridge between two copper centers, forming a coordination polymer, is studied. The solid state structure of this Cu(I)-isox′ 1D coordination polymer is also reported.     

Synthesis and Characterization of Poly(tetramethyl-1,4-silphenylenesiloxane) Derivatives with Oxyethylene Substituent on Phenylene Moiety

Summary Novel poly(tetramethyl-1,4-silphenylenesiloxane) derivatives having 2-methoxy-ethoxy or 2-(2-methoxyethoxy)ethoxy substituents at both 2- and 5-positions on phenylene moieties were synthesized and characterized by differential scanning calorimetry and thermogravimetry analyses. Poly(tetramethyl-1,4-silphenylene-siloxane) derivatives were obtained by condensation polymerization of the corresponding disilanol derivatives, i.e., 1,4-bis(dimethylhydroxysilyl)-2,5-bis(2-methoxyethoxy)benzene and 1,4-bis(dimethylhydroxysilyl)-2,5-bis[2-(2-methoxy-ethoxy)ethoxy]benzene, which were prepared by the Grignard reaction using chlorodimethylsilane and the corresponding dibromobenzene derivatives followed by the hydrolyses, catalyzed by palladium on charcoal. The introduction of 2-methoxyethoxy groups on the phenylene moiety made the melting point high, compared with poly(tetramethyl-1,4-silphenylenesiloxane); however, that of 2-(2-methoxyethoxy)ethoxy groups made it low, indicating the longer oxyethylene moiety induced the lowering of the melting point. There were no significant differences in the thermostabilities of both present polymers, suggesting the length of oxyethylene moiety would not affect the thermostability, though the introduction of polar oxyethylene group onto the phenylene moiety induced a decline of thermostability.     

Fused Polycyclic Hydrocarbons Through Superacid-Induced Cyclialkylation of Aromatics

Benzene and substituted derivatives (toluene, ortho-xylene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, anisole), when applied in large excess, react with 1,4 diols (pentan-1,4-diol, hexan-2,5-diol, and 2,5-dimethylhexan-2,5-diol) or an oxolane (2,2,5,5-tetramethyltetrahydrofuran) in the presence of the Brønsted superacid trifluoromethanesulfonic acid (triflic acid, TFSA) to afford substituted tetralins in excellent yields with high selectivity. Reacting benzene with a small excess of alkylating agents yields octahydroanthracenes. The transformation of naphthalene with oxolane leads to a partially saturated octamethyloctahydrotetracene under similar conditions. Product formation is interpreted by intermolecular Friedel-Crafts alkylation followed by cyclialkylative ring closure.     

SYNTHESIS OF DIHYDRODIOLS OF PHENANTHRO[3,4-b]THIOPHENE AND PHENANTHRO[4,3-b]THIOPHENE

A number of sulfur analogs of polynuclear aromatic hydrocarbons (thia-PAHs) have been identified in cigarette smoke condensate. Phenanthro[3,4-b]thiophene (P[3,4-b]T) and phenanthro[4,3-b]thiophene (P[4,3-b]T) are sulfur analogs of benzo[c]phenanthrene, which is known to be metabolized to one of the most tumorigenic fjord region diol epoxides tested thus far. Although fjord region diol epoxides of P[3,4-b]T and P[4,3-b]T are expected to be potent mutagens and tumorigens, these two thia-PAHs differ greatly in their mutagenic potencies. In contrast to P[3,4-b]T which is as mutagenic as benzo[a]pyrene, its isoster P[4,3-b]T is a nonmutagenic compound. In order to understand the basis underlying the difference in the mutagenic potency of P[3,4-b]T and P[4,3-b]T, we require these thia-PAHs and their dihydrodiol derivatives for investigating their metabolism and mutagenic/carcinogenic activity. In these studies, we have investigated the Suzuki cross-coupling reaction for an abbreviated synthesis of P[3,4-b]T, P[4,3-b]T, and their dihydrodiol derivatives from easily available reagents.     

Divergent Synthesis and Evaluation of the in vitro Cytotoxicity Profiles of 3,4-Ethylenedioxythiophenyl-2-propen-1-one Analogues

A new series of 3,4-ethylenedioxythiophene (EDOT)-appended propenones were prepared by condensation reaction and their in vitro cytotoxicity effects were evaluated against five human cancer cell lines. Preliminary structure–activity relationships of EDOT-incorporated 2-propenone derivatives were also established. The EDOT-appended enones demonstrated significant cytotoxicity against human cancer cell lines. The most active analogue, (E)-3-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one ( 3 p , GI₅₀=110 nm ), severely inhibited the clonogenic potential of cancer cells, and induced cell-cycle arrest in the G2/M phase and caused an accumulation of HCT116 colon cancer cells with >4 N DNA content. Also, 3 p exhibited weak inhibition of the enzymatic activity of human topoisomerase I. Molecular docking studies indicated preferential binding of the compounds to the ATP-binding pocket of the human checkpoint 2 kinase (Chk2) catalytic domain, thus, identifying a novel diaryl 2-propenone chemotype for the development of potent inhibitors of Chk2.     

A facile synthesis of some novel fused [1,2,4]triazolo[3,4-b][1,3,4]thiadiazol derivatives

A series of novel 3-[6-(4-substituted phenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-3-ylmethyl]-5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidin-4(3H)-one derivatives (7a–7h) have been synthesized from 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile (1) through a multi-step reaction sequence. The key intermediate (6) on condensation with various substituted aromatic carboxylic acids in the presence of phosphorus oxychloride afforded the series of title compounds (7a–7h). The structures of all newly synthesized compounds were established on the basis of their IR, ¹H-NMR, ¹³C-NMR and liquid chromatography mass spectrometry spectral data.     

An efficient microwave-assisted synthesis of thieno[2,3- b ]quinolines under solvent-free conditions

A novel and efficient method for the synthesis of substituted thieno[2,3-b]quinolines has been developed. A simple one-pot reaction of 3-formyl-2-mercaptoquinolines 2a–l with 1-chloroacetone, 2-chloroacetamide, ethyl chloroacetate and 2-chloro-1-phenylethanone in presence of catalytic amount of potassium carbonate under microwave irradiation and solvent-free conditions gave thieno[2,3-b]quinolin-2-ylethanone derivatives 3a–e, thieno[2,3-b]quinoline-2-carboxamide derivatives 4a–e, ethyl thieno[2,3-b]quinoline-2-carboxylate 5a–e and phenyl(thieno[2,3-b]quinolin-2-yl)methanone derivatives 6a–e compounds respectively. The structures of all the newly synthesised compounds were elucidated on the basis of elemental analysis, IR, ¹H NMR and mass spectral data.     

Synthesis and characterization of poly(tetramethylsilarylenesiloxane) derivatives bearing benzodithiophene moieties

Poly(tetramethylsilarylenesiloxane) derivatives bearing benzo[1,2-b;4,5-b′]dithiophene (P1) and benzo[2,1-b;3,4-b′]dithiophene (P2) moieties were prepared via polycondensation of the corresponding disilanol monomers, that is, 2,6-bis(dimethylhydroxysilyl)benzo[1,2-b;4,5-b′]dithiophene (M1) and 2,7-bis(dimethylhydroxysilyl)benzo[2,1-b;3,4-b′]dithiophene (M2), respectively. It was deduced that P1 is a crystalline polymer while P2 is an amorphous one from the results of differential scanning calorimetry (DSC). Bathochromic and hyperchromic effects were observed in the absorption and fluorescence spectra when dimethylsilyl substituents were introduced on the benzo[1,2-b;4,5-b′]dithiophene and benzo[2,1-b;3,4-b′]dithiophene skeletons. The fluorescence quantum yields (Φ_Fs) were not improved by the introduction of dimethylsilyl groups onto the benzo[1,2-b;4,5-b′]dithiophene and benzo[2,1-b;3,4-b′]dithiophene skeletons, whereas the improvement in the Φ_Fs was remarkable in the case of poly(tetramethylsilarylenesiloxane) derivatives that possessed the corresponding fused benzene ring systems, i.e., poly(tetramethyl-2,6-silanthrylenesiloxane) and poly(tetramethyl-1,8-silphenanthrylenesiloxane).     

Synthesis and Antimicrobial Evaluation of Some Novel Bis-α,β-Unsaturated Ketones,Nicotinonitrile, 1,2-Dihydropyridine-3-carbonitrile,Fused Thieno[2,3-b]pyridine and Pyrazolo[3,4-b]pyridine Derivatives

The title compounds were prepared by reaction of 1,1′-(5-methyl-1-phenyl-1H-pyrazole-3,4-diyl)diethanone (1) with different aromatic aldehydes 2a–c, namely Furfural (2a), 4-chlorobenzaldehyde (2b) and 4-methoxybenzaldhyde (2c) to yield the corresponding α,β-unsaturated ketones 3a–c. Compound 3 was reacted with malononitrile, 2-cyanoacetamide or 2-cyanothioacetamide yielded the corresponding bis[2-amino-6-(aryl)nicotinonitrile] 4a–c, bis[6-(2-aryl)-2-oxo-1,2-dihydropyridine-3-carbonitrile] 5a–c or bis[6-(2-aryl)-2-thioxo-1,2-dihydropyridine-3-carbonitrile] 6a,b, respectively. The reaction of compound 6a with each of 2-chloro-N-(4-bromophenyl) acetamide (7a), chloroacetamide (7b) in ethanolic sodium ethoxide solution at room temperature to give the corresponding 4,4′-(5-methyl-1-phenyl-1H-pyrazole-3,4-diyl)bis-6-(2-furyl)thieno[2,3-b]pyridine-2-carboxamide] derivatives 9a,b. While compound 6a reacted with hydrazine hydrate yielded the 4,4′-(5-methyl-1-phenyl-1H-pyrazole-3,4-diyl)bis[6-(2-furyl)-1H-pyrazolo[3,4-b]pyridin-3-amine] 11. The structures of the products were elucidated based on their spectral properties, elemental analyses and, wherever possible, by alternate synthesis. Antimicrobial evaluation of the products was carried out.     

Synthesis and antimicrobial evaluation of some pyrazolo-thiazolyl alkoxy-1H-isoindole-1, 3(2H)-dione derivatives

1,3-Thiazolidine-2,4-dione 2 has been synthesized by the cyclisation reaction of thiourea and chloroacetic acid in the presence of ethanol. The reaction of compound 2 with substituted aromatic aldehyde afforded the corresponding derivatives of substituted 5-benzylidene-1,3-thiazolidinone-2,4-dione 3a–d, which upon reflux with ω-bromoalkoxyphthalimide gave 2-{[-5-(substituted benzylidine)-2,4-dioxo-1,3-thiazolidine-3-yl]alkoxy} -1H-isoindole-1,3(2H)-dione 4a–i. Further, compounds 4a–i were treated with phenyl hydrazine and 2,4 dinitro phenyl hydrazine in the DMF to yield the title compound 2-[5-oxo-2,3-substituted diphenyl-2H-pyrazolo[3,4-d][1,3]thiazol-6(5H)-yl)alkoxy]-1H-isoindole-1,3(2H)-dione 5a–r. Structures of newly synthesized compounds were established based on elemental analysis, IR, ¹H NMR and mass spectral data. Synthesized compounds have been assayed for their antibacterial activities against B. subtilis, K. pneumoniae, P. aeruginosa and S. aureus and antifungal activities against A. fumigatus and C. albicans.     

Synthesis of highly fluorescent coumarinyl chalcones derived from 8-acetyl-1,4-diethyl-1,2,3,4-tetrahydro-7H-pyrano[2,3-g]quinoxalin-7-one and their spectral characteristics

A series of novel coumarin based chalcones were synthesized by the classical crossed aldol condensation reaction of 8-acetyl-1,4-diethyl-1,2,3,4-tetrahydro-7H-pyrano[2,3-g]quinoxalin-7-one and various substituted benzaldehydes. These novel ketocoumarin derivatives having a 1,4-diethyl-1,2,3,4-tetrahydroquinoxaline framework exhibited brilliant fluorescence. The novel chalcones absorbed in the range of 458-523 nm in various solvents. The wavelength of maximum absorption of these chalcones was found to be significantly longer than their simple acyl derivative known in the literature. The dyes displayed longer wavelength of absorption in the high polarity solvents compared to non-polar solvents. Thermogravimetric analysis of the chalcones revealed that the chalcones possess good thermal stability.     

Direct (hetero)arylation polymerization for the synthesis of donor–acceptor conjugated polymers based on N‐benzoyldithieno [3,2‐b:2′,3′‐d]pyrrole and diketopyrrolopyrrole toward organic photovoltaic cell application

In this research, new donor–acceptor (D‐A) photovoltaic polymers were synthesized from dithieno[3,2‐b:2′,3′‐d]pyrrole electron donor derivatives, including N‐benzoyldithieno[3,2‐b:2′,3′‐d]pyrrole and N‐(4‐hexylbenzoyl)dithieno[3,2‐b:2′,3′‐d]pyrrole, in combination with the electron deficient unit 2,5‐bis(2‐ethylhexyl)‐3,6‐di(thiophen‐2‐yl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione via direct (hetero)arylation polymerization. The D‐A conjugated polymers obtained were characterized via ¹H NMR, gel permeation chromatography, Fourier transform infrared spectroscopy, DSC, XRD, photoluminescence and UV–visible methods. In addition, these D‐A polymers were used as activated layers in bilayer and bulk heterojunction structures for the fabrication of organic photovoltaic cells. © 2019 Society of Chemical Industry