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Abstract 1,4-dihydro-1,2,4,5-tetraarylpyrrolo[3,2-b]pyrroles are a versatile class of materials with simple synthesis and promising application in organic electronic devices. In this work we present a method of synthesis of new 1,4-dihydro-1,2,4,5-tetraarylpyrrolo[3,2-b]pyrrole derivatives, with ester and carboxylic acid groups as anchoring groups, by multicomponent reactions using niobium pentachloride as catalyst. The new materials were structurally and optically characterized. Also, it was compared the bonding of different moieties to the titanium dioxide mesoporous film. The preliminary tests as dyes in standard configuration in dye-sensitized solar cells have shown a potential performance in the energy conversion.

Abstract 5-Hydroxy-1-phenyl-1H-pyrazole-3-carboxylic acid was selected as the coupling component to react with three S /N-containing heterocyclic (2-amino-4-chloro-5-formylthiophene-3-carbonitrile, 5-nitrobenzo[c]isothiazol-3- amine, 5-amino-1-ethyl-6-hydroxy-4-methyl-2-oxo-1,2-dihydropyridine-3- carbonitrile) diazo salts and three aniline derivatives with different electron-pulling/electron-pushing substituents, so as to produce six carboxylic pyrazolone based mono-/bi-heterocyclic dyes. Our results show that λmax of carboxylic pyrazolone based heterocyclic dyes depends on the substituent effects on aromatic rings and type of the heterocyclic rings. Compared with methyl pyrazolone/2,3-dimethylaniline based mono-heterocyclic dye, corresponding carboxylic pyrazolone based one with stronger D–π–A system brings a red shift of 37 nm. In contrast, carboxylic pyrazolone/thiophene and carboxylic pyrazolone/benzisothiazole based bi-heterocyclic dyes display blue shifts of 39 and 47 nm compared with relative methyl pyrazolone ones because of the role transformation for donor and acceptor (D−π−A to A−π−D) originating from the electron-withdrawing groups of S-containing heterocycles. Furthermore, different azo ⇌ hydrazone tautomeric transformations have been confirmed by the acid-base titration experiments. Namely, the mono-heterocyclic dyes, which would be transferred into the azo form in the alkaline condition, exhibit dominating hydrazone form in MeOH. However, the azo form of bi-heterocyclic dyes, which would convert to the hydrazone one under the acidic condition, is overwhelming in MeOH. Graphical abstract Image 1 Highlights • Six carboxylic pyrazolone based heterocyclic dyes were synthesized. • λ max of dyes depends on the substituents and type of the heterocyclic rings. • D− π −A to A− π −D transformation is found by comparing to methyl pyrazolone dyes. • Different azo ⇌ hydrazone tautomerism is observed for mono-/bi-heterocyclic dyes. [ABSTRACT FROM AUTHOR]

Abstract Derivatives of 1,3-naphthoxazines containing from five to seven-membered spiro ring – under Vilsmeier–Haack reaction conditions are rearranged into novel xanthene-type compounds. All synthesized aminochromene derivatives fluoresce in organic solvents with extra large Stokes shifts (100–133 nm). It was found that compounds containing five-membered annulated aliphatic rings in methanol solution have the best spectral characteristics. These compounds have moderate quantum yields of 28.36–28.94%, and extra large Stokes shifts 106 and 115 nm. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract By a reaction of 4-formyl-2,3-dihydro-1 H -xanthen-9-yl derivative with substituted anilines and hydrazine hydrate the novel Schiff bases and corresponding aldazine were synthesized. The structures of these compounds and their correlation with spectral properties were investigated by FTIR, NMR, mass-spectrometry, moreover Schiff base with anthranilic acid and aldazine were also confirmed by X-Ray diffraction analysis. Obtained compounds have absorption maxima in the range of 431–512 nm in acetonitrile. The most long-wavelength absorption exhibit Schiff bases with anthranilic acid and only this compound demonstrate noticeable fluorescence in yellow part of the spectra, probably due to intramolecular hydrogen bonding and its zwitter-ionic structure. Aldazine derivative show pronounced acidochromic properties with long-wavelength shift from 505 nm to 610 nm upon acidifying and can be used for detection of negligible amount of acid on organic media. Graphical abstract Image 1 Highlights • Novel xanthene chromophores and fluorophores were obtained by Schiff's reaction. • Schiff base with anthranilic acid exhibits fluorescence in yellow region. • Novel acidochromic azine dye were prepared. [ABSTRACT FROM AUTHOR]

Abstract Two pairs of isomeric heterocyclic dyes were synthesized successfully by diazotization reactions between the common 1-phenyl-3-methyl-5-pyrazolone coupling component and 2-aminobenzoic/4-aminobenzoic acid as well as 2-amino-5-nitrophenol/2-amino-3-nitrophenol. The introduction of additional carboxyl and hydroxyl groups in the phenyl ring makes them good multidentate chelating ligands in terms of coordination chemistry, and three Cu(II) and one Fe(II) dye-metal complexes were then produced showing different deprontonated states in ligands (monovalent and divalent), metal-ligand ratios (1:1 and 1:2) and structural diversity (mononuclear, dinuclear and one-dimensional chain). Red shifts of 3–6 nm in the UV–Vis spectra are observed for the ortho -COOH and ortho -NO 2 dyes compared with corresponding para substituted ones, which could be supported by the formation of fused six-membered intramolecular hydrogen-bonding rings found in their single-crystal structures involving the hydrazone protons. More interesting, different from our previously reported solvent and pH induced hydrazone to azo-keto transformation, another kind of hydrazone to azo-enol transformation has been observed for our pyrazolone based dyes in addition to conventional hydrazone to deprotonated azo transformation after metal-ion complexation. Graphical abstract Image 1 Highlights • Two pairs of isomeric pyrazolone based heterocyclic dyes were synthesized. • Four Cu(II) and Fe(II) dye-metal complexes were then produced. • Different deprontonated states, metal-ligand ratios and structural diversity are found. • Hydrazone to deprotonated azo/azo-enol transformation is observed. [ABSTRACT FROM AUTHOR]

The newly synthesized 2-((2-amino-4,6-dimethylpyrimidine-5yl)diazenyl)benzoic acid has been prepared by diazotization of anthranilic acid and coupling with 2-amino-4,6-dimethylpyrimidine. Its structure has been characterized by spectroscopic measurements ( 1 H NMR spectra, FT-IR spectra, mass spectra and UV–visible spectra) and thermal analysis technique. The DNA cleavage activity of compound is evaluated by agarose gel electrophoresis with a series of concentrations. Our measurements show that neither a disruptive effect created by 2-((2-amino-4,6-dimethylpyrimidine-5yl)diazenyl)benzoic acid on pBR 322 DNA are observed, nor the dependence of the concentration on the activity of newly synthetized chemical on pBR 322 plasmid DNA such as cleavage or break DNA double helix structure. Moreover, computational chemistry method based on Density Functional Theory (DFT) employing B3LYP level with 6-31G(d) basis set has been used to study geometry and spectroscopic properties such as FT-IR and UV–vis spectra of the titled compound considered in this work. The computations of the chemical shifts for 1 H NMR of the title compound have been carried out via Gauge-Invariant Atomic Orbital (GIAO) method utilizing the same basis set. It is observed that DFT results are compatible with the experimental results. [ABSTRACT FROM AUTHOR]

Spectral properties of five derivatives of 4-aminochromene containing formylated partially hydrogenated five or six-membered cycles, and two derivatives of 4-aminochromen-2-ylidene-malonaldehyde have been studied. The cyclic derivatives absorb light with the maxima around 430, nm and emit near 550 nm with a luminescence quantum yield of 0.056–0.135 in acetonitrile solution. The non-cyclized derivatives of 4-aminochromene with a malonaldehyde moiety possess emission in solid state in the red region with a moderate Stokes shift of 43 nm and 67 nm. Derivatives of 4-aminochromene containing formylated partially hydrogenated five or six-membered cycles were derivatized with active CH-acids to give seven Knoevenagel condensation products. Absorption spectra of these condensation products in acetonitrile solutions are red-shifted by 102–184 nm, while emission maxima are red-shifted by only 71–117 nm, as compared to the corresponding initial formyl derivatives. In addition, the condensation products have 1.5–1.9 times higher extinction coefficient (60,600–79,600 M −1 cm −1 ), while fluorescence quantum yields decreased to (0.003–0.034). [ABSTRACT FROM AUTHOR]

Four new azo dyes: 2-[(3,5-diamino-1 H -pyrazol-4-yl)diazenyl]-5-nitrobenzoic acid (A) , 2-[(3-hydroxy-5-methyl-1 H -pyrazol-4-yl)diazenyl]-5-nitrobenzoic acid (B) , 2-[(3,5-dimethyl-1 H -pyrazol-4-yl)diazenyl]-5-nitrobenzoic acid (C) and 2-[(5-amino-3-methyl-1 H -pyrazol-4-yl)diazenyl]-5-nitrobenzoic acid (D) which have the same 4-nitrobenzene/azo/pyrazole skeleton and different substituted groups are synthesized in this work. The structures and spectroscopic properties of these new azo dyes are characterized by using spectroscopic methods such as FT-IR, 1 H NMR, 13 C NMR and UV–vis. Their solvatochromic properties in chloroform, acetic acid, methanol, dimethylformamide (DMF) and dimethylsulphoxide (DMSO) are studied. Moreover, molecular structures and some spectroscopic properties of azo dyes are investigated by utilizing the quantum computational chemistry method based on Density Functional Theory (DFT) employing B3LYP hybrid functional level with 6-31G(d) basis set. It is seen that experimental and theoretical results are compatible with each other. [ABSTRACT FROM AUTHOR]

Synthetic strategy of functional group transformation has been utilized to modify the acidic hydroxyl (−OH) of a series of pyridone based heterocyclic dyes into basic secondary amine (−NHCH 2 CH 2 CH 2 OCH 3 ), so as to improve the color instability of hydrazone dyes under the basic condition. Namely, five pairs of 6-(3-methoxypropylamino)pyridin-2-one based azo dyes have been synthesized showing significantly increased pH stability, which can be verified by corresponding UV–Vis spectra. Successful configuration transformation from the NH N= unit in the hydrazone dyes into the N N− one in the resultant azo dyes is believed to obstruct the proton transfer between the pyridone and azo/hydrazone units (azo-hydrazone tautomerism), thereby enhancing the pH stability especially under the alkaline condition. In addition, different N -substituted groups at the pyridone ring and push-pull electronic substituted groups at the phenyl ring have been selected to make spectral and structural comparisons before and after the functional group transformation. [ABSTRACT FROM AUTHOR]

The newly synthesized thirteen disazo dyes containing imidazole and pyrazole cycles (3a-3m) were carried out by diazotization reaction of 5-amino-4-arylazo-3-methyl-1H-pyrazoles (2a-2m) and coupling reaction with 1-methyl imidazole. Structures of synthesized azo dyes were characterized by UV–Vis, FT-IR,1H-NMR, elemental analysis and their solvatochromic properties were studied in DMSO, DMF, methanol, acetic acid and chloroform. In addition, the antimicrobial activities of dyes against twelve pathogenic bacteria were examined in detail and all dyes showed antimicrobial activity against different bacterial strains. [ABSTRACT FROM PUBLISHER]

A series of pyrazolone-based full heterocyclic and half heterocyclic hydrazone dyes as well as aniline modified hydrazone-azomethine dyes has been successfully synthesized and spectrally characterized. UV–Vis spectral comparisons indicate that the aniline modified hydrazone-azomethine dyes show significant red shifts compared with their common full heterocyclic precursor and respective half heterocyclic dyes with the same substituents in the absence of the 2-aminothiophene moiety. The incorporation of CH N and NH N units in the targeting hydrazone-azomethine dyes, which results in the increase of the π -conjugated system, is responsible for the bathochromic shifts in the UV–Vis spectra. Furthermore, solvatochromism and acid-base titration experiments have been carried out to explore the possible proton transfer within the multiple heteroatoms for this family of compounds. Our results demonstrate the existence of an equilibrium between the hydrazone and azo-keto tautomers and the transformation can be driven by the polarity of solvents and pH values. In addition, the easily deprotonated azo-enol tautomer is unlikely to be formed because of the alkaline stability in both organic solvents and water for this series of pyrazolone-based heterocyclic dyes. [ABSTRACT FROM AUTHOR]

We reported herein the studies on in situ metal-ion complexation and H 2 O 2 oxidation for a pyridine-2,6-dione based heterocyclic dye (C.I. Disperse Yellow 211) in the hydrazone-tautomeric form. Our results reveal that four kinds of compounds can be isolated successfully by treating this dye with Cu(OAc) 2 ·H 2 O and H 2 O 2 in the presence of NH 3 ·H 2 O and DMF, namely oxidation and complexation product 1 , oxidation product 2 , ring-degradation (ring-opening and oxidative cleavage) product 3 and complexation product 4 . In contrast, when copper(II) and nickel(II) ions were used under the similar reaction condition just in the absence of H 2 O 2 oxidant, only direct complexation products 4 and 5 could be obtained. It is noted that organic compounds 2 and 3 adopt the same hydrazone-tautomeric form as that in C.I. Disperse Yellow 211, but all three dye-metal complexes 1 and 4 – 5 exhibit the deprotonated azo form. A possible reaction mechanism is proposed for the formation of hydroxyl-addition and ring-degradation products 1 – 3 . Furthermore, we have provided an effective preparation method for new dyes with an additional ortho phenolic hydroxyl group by H 2 O 2 oxidation, metal-ion complexation and subsequent demetallization by Na 2 S. [ABSTRACT FROM AUTHOR]

Twenty-one novel pyrazole azo compounds were synthesized by coupling 3-amino-5-hydroxy-1 H-pyrazole and 3-amino-1-phenyl-2-pyrazoline-5-one with diazonium salts derived from aniline, o, m, and p-nitroaniline, o and p-methoxyaniline, o, m, and p-chloroaniline, and o, m, and p-methylaniline. Spectroscopic data for these dyes, dissolved in six solvents, were measured. The effects of acid and base on the visible absorption spectra of the dyes are also reported. The structures of all the compounds were confirmed by Fourier-transform infrared spectroscopy, mass spectroscopy, ultraviolet and visible electronic absorption spectroscopy, nuclear magnetic resonance spectroscopy, and elemental analysis. In addition, the antimicrobial activity of the dyes against six pathogenic bacteria were examined in detail. [ABSTRACT FROM AUTHOR]

The first structural report of an S -containing heterocycle based pyrazolone dye, 3-methyl-4-((6′-methylbenzo[ d ]thiazol-2′-yl)hydrazono)-1-phenyl-5-pyrazolone ( 1 ), is presented. The compound exhibits the hydrazone-tautomeric form. Treatment of 1 with a mixture of ammonia and acetone results in the formation of an acid-base adduct, 2 , consisting of the deprotonated dye as anion and in-situ formed 2,2,6,6-tetramethylpiperidone as the cation. This acid-base adduct was investigated by crystal structure determination. Comparison of the related bonds in both compounds, 1 and 2 , confirmed the formation of the anion. [ABSTRACT FROM AUTHOR]

Synthesis of new disazo indole dyes ( 3a – 3m ) was carried out by diazotization of 5-amino-4-arylazo-3-methyl-1H-pyrazoles ( 2a – 2m ) and coupling with 2-phenyl indole. The newly synthesized 12 disperse disazo dyes were characterized by UV–vis, FT-IR, 1 H NMR and elemental analysis. Their solvatochromic properties in different solvents were investigated. In addition, theoretical calculations are performed for the disazo dyes. The molecular structures of all synthesized dyes 3a – 3m have been optimized to the global minima at the levels of using HF and DFT methods with 6-31G(d), 6-311G(d), 6-311++G(d,p), and 6-31++G(d,p) basis sets. [ABSTRACT FROM AUTHOR]

• Synthesized 4a- 4h dyes' binding affinities evaluated for reference proteins. • All compounds except 4b had higher affinities compared to reference drug molecules. • Stability of the complexes for best resulting molecules were evaluated. • 4c, 4d and 4g remained in binding pockets during the 30 ns MD simulation. • 4c-HSP90α, 4d-COVID-19 mpro & AChE and 4 g-NNMT complexes are stable in simulation. In the study, by using 5-amino-4-arylazo-3-methyl- 1H -pyrazole derivatives and 2‑hydroxy-5-(phenyldiazenyl) benzaldehyde; eight novel heterocyclic disperse disazo-azomethine dyes were synthesized, their chemical structures were characterized via FT-IR and 1H NMR studies. Synthesized compounds were also investigated computationally by performing various techniques. In the computational part of the study, geometry optimizations, frequency analyses, frontier molecular orbital (FMO) calculations, molecular electrostatic potential (MEP) map calculations, FT-IR and NMR spectral analyses were performed on the compounds. Additionally, to reveal their potentials against SARS-CoV-2 main protease (SARS-CoV-2 Mpro), acetylcholine esterase (AChE), heat shock protein (HSP90α) and nicotinamide N -methyl transferase (NNMT), molecular docking calculations were also performed on the synthesized compounds. Molecular dynamics (MD) simulations were carried out on the top-scoring ligand-receptor complexes to evaluate the stability of the complexes and the interactions between ligands and receptors in more detail. Results showed that synthesized compounds can interact with all these four receptors effectively and can be promising structures for further studies. [ABSTRACT FROM AUTHOR]

• The effect of the amidine fragment on the spectral properties of xanthene dyes was studied. • Synthesis and characterization of a novel acidochromic benzoxanthene derivatives. • Synthesis and characterization of a new NIR dye. • Determination of X-ray single crystal structure. We synthesized a series of new xanthene dyes containing dimethylamidine group and investigated the influence of this fragment in the composition of xanthene dyes on their spectral characteristics. The amidine fragment mainly affects the absorption and emission maxima due to the π-conjugation of this substituent with xanthene moiety which leads to red shifts by 41–90 nm in the spectra. The most long-wavelength dye, derivative with 1,3,3-trimethyl-3 H -indolium, have an absorption maximum at 661 nm, and an emission at 701 nm in methanol. The addition of a large excess of trifluoroacetic acid to the solution of this dye lead to a hypsochromic shift of absorption maximum to 585 nm, which is associated with the protonation of the amidine substituent. The absorption spectra of the corresponding compounds without amidine fragment after addition of trifluoroacetic acid remain almost identical, which proved the π-conjugation of the amidine fragment, but not only oxygen of xanthene moiety. Image, graphical abstract [ABSTRACT FROM AUTHOR]