Spectroscopic studies of keto–enol tautomeric equilibrium of azo dyes

Rauf, Muhammad; Hisaindee, Soleiman; Saleh, Na’il

doi:10.1039/c4ra16184j

Cited by 89 publications

(39 citation statements)

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“…Arylhydrazones are characterized by their simple preparation and worth considering in the design of novel molecular switches with solvatochromic and pH sensing performance. A hydrazone functional group has the ability to operate as a bridge in a donor-acceptor molecular structure, or it can act itself as an electron donor moiety, when it is in conjugation with an electronwithdrawing moiety [34][35][36][37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Solvatochromic Performance, pH Sensing, Dyeing Ability, and Antimicrobial Activity of Novel Hydrazone Dyestuffs

Khattab

Allam

Othman

et al. 2019

Journal of Chemistry

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New tricyanofuran intramolecular charge transfer dyes comprising the hydrazone group were prepared and fully characterized in order to study their possible solvatochromism, dyeing ability, and antimicrobial activity. e preparation of the hydrazone dyes was achieved in relatively good yields starting from different aromatic amines. e hydrazone functional group was presented via the azo-coupling reaction of the tricyanofuran compound by the properly substituted diazonium chloride. Chemical structures of the prepared hydrazones were confirmed via nuclear magnetic resonance spectroscopy ( 1 H-and 13 C-NMR), Fourier-transform infrared spectroscopy (FT-IR), and elemental analysis (C, H, and N). e UV-visible absorption spectra of the produced sensor colorants displayed interesting solvatochromism in solvents with a different polarity, which was found to be affected by the substituents bonded to the aromatic hydrazone moiety. e pH molecular switching was investigated through tuning the intramolecular charge transfer stimulated by the reversible deprotonation/protonation process in acetonitrile solution showing color change from yellow to purple. e produced disperse dyestuffs were employed for dyeing polyester fibers to introduce acceptable color strength and colorfastness properties. Moreover, the dyes verified a weak to moderate antimicrobial activity against some selected pathogens, including S. aureus, E. coli, and Candida albicans.

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Section: Introductionmentioning

confidence: 99%

Synthesis, Solvatochromic Performance, pH Sensing, Dyeing Ability, and Antimicrobial Activity of Novel Hydrazone Dyestuffs

Khattab

Allam

Othman

et al. 2019

Journal of Chemistry

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“…It seems that the intramolecular hydrogen bond suppressed the rapid tautomerization between keto‐Z‐enol‐azo 4[I] and diketo‐hydrazone 4[II] forms. These dyes may undergo rapid tautomerization that causes two isomeric forms without lifetimes long enough in NMR time scale and depends on solvent polarity . Representatively, expanded 1 H NMR spectrum of the deshielded proton in 4c is shown in Fig.…”

Section: Resultsmentioning

confidence: 97%

“…Many of the azo dyes show azo‐hydrazone tautomerism . The 1 H and 13 C NMR spectroscopy techniques are powerful tools for the elucidation of the predominant tautomeric forms . 13 C NMR spectrum of dyes 4a–4e showed two methyl peaks at aliphatic region and confirmed the existence of at least two tautomeric forms (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The 1 H NMR spectra revealed the OH resonance of the keto‐Z‐enol–azo ( 4[I] ) form in CDCl 3 solution, while in the 13 C NMR spectra, the keto‐Z‐enol–azo ( 4[I] ) CO resonance appeared in the higher field range. The data indicated that the tautomeric equilibria depend on the solvent and the substituents in the phenyl ring . Thus, the tautomeric balance shifts to the diketo‐hydrazone ( 4[II] ) form by decreasing the solvent polarity that also depends on the electron‐withdrawing properties of the phenyl ring substituent …”

Section: Resultsmentioning

confidence: 99%

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Isotopic splitting patterns in the ¹³C NMR spectra of some partially deuterated 1‐aryl‐2‐(phenyldiazenyl)butane‐1,3‐dione and 4‐hydroxy‐3‐(phenyldiazenyl)‐2H‐chromen‐2‐one: evidence for elucidation of tautomeric forms

Pesyan

Rashidnejad

2016

Magnetic Reson in Chemistry

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Aims & scope MRC is devoted to the rapid publication of papers which are concerned with the development of magnetic resonance techniques, or in which the application of such techniques plays a pivotal part. Contributions from scientists working in all areas of NMR, ESR and NQR are invited, and papers describing applications in all branches of chemistry, structural biology and materials chemistry are published. The journal is of particular interest not only to scientists working in academic research, but also those working in commercial organisations who need to keep up-to-date with the latest practical applications of magnetic resonance techniques. 54(5) 347-414 (2016) ISSN 0749-1581 347 Q.E.COSY: determining sign and size of small deuterium residual quadrupolar couplings using an extended E.COSY principle 351-357 P. Tzvetkova and B. Luy The Q.E.COSY as an extension of the E.COSY principle allows the sign sensitive measurement of residual quadrupolar couplings in partially aligned samples even in cases where corresponding splittings are not resolved in the deuterium 1D spectrum. Several experimental demonstrations are given. Isotopic splitting patterns in the 13 C nuclear magnetic resonance spectra of some partially deuterated 1-aryl-2-(phenyldiazenyl)butane-1,3-dione and 4-hydroxy-3-(phenyldiazenyl)-2H-chromen-2-one were investigated: CDCl 3 and/or DMSO-d6 with addition of two drops of D 2 O. All dyes showed intramolecular hydrogen bonding. Among ten dye samples, two dyes derived from benzoylacetone did not show deuteration, three dyes showed partial deuteration and five dyes showed full deuteration under similar conditions. wileyonlinelibrary.com/journal/mrc MRC Contents continued overleaf Contents continued Hopping and residence times of water on biochar surface have been measured by fast field cycling NMR relaxometry. These were related to biochar wettability. NMR results accorded with those from contact angle measurements, thereby indicating that the former technique is a valid alternative to the latter. Advantage of relaxometry over contact angle measurements lies in the possibility to obtain not only wettability, but also mechanisms of water molecular dynamics on biochar surface, thereby leading to the understanding of its role in increasing soil quality and plant nutrition. Evaluation of the surface affinity of water in three biochars using fast field cycling NMR relaxometry 365-370

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“…The intramolecular hydrogen-bond interactions in the half-salen moieties cause the excited-state intramolecular proton-transfer (ESIPT) [60,61] known to lead to emission in solution [46,59,[61][62][63][64][65][66]. The same effect is known to occur in the solid state [12,67] if the intramolecular H-bond produce hindrance to the torsion of sterically encumbered parts of the molecule [57,68,69].…”

Section: Resultsmentioning

confidence: 99%

A Novel DR/NIR T-Shaped AIEgen: Synthesis and X-Ray Crystal Structure Study

et al. 2020

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We developed a new benzodifuran derivative as the condensation product between 2,6-diamino -4-(4-nitrophenyl)benzo [1,2-b:4,5-b']difuran-3,7-dicarboxylate and 3-hydroxy-2-naphthaldehyde. The intramolecular hydrogen-bond interactions in the terminal half-salen moieties produce a sterically encumbered highly conjugated main plane and a D-A-D (donor-acceptor-donor) T-shaped structure. The novel AIEgen (aggregation-induced enhanced emission generator) fulfils the requirement of RIR (restriction of intramolecular rotation) molecules. DR/NIR (deep red/near infrared) emission was recorded in solution and in the solid state, with a noteworthy photoluminescence quantum yield recorded on the neat crystals which undergo some mechanochromism. The crystal structure study of the probe from data collected at a synchrotron X-ray source shows a main aromatic plane π-stacked in a columnar arrangement.Crystals 2020, 10, 269 2 of 15 law [20][21][22] the intrinsic low band-gap of such DR/NIR emitters makes them especially vulnerable to the ACQ effect [23] due to higher vibrionic coupling between the ground and excited states. Therefore, most of the AIEgens reported emit blue and green lights. Although they are highly sought after for red OLEDs (Organic Light Emitting Diodes), night-vision devices, secured displays, optical waveguides and in the wide field of bio and chemo-sensing [24][25][26][27][28], there are fewer efficient DR/NIR (deep red/near infrared) materials. Of particular interest are AIE fluorophores with intense emission at DR/NIR region owing to their deep tissue penetration, photo-stability and minimum interference in living systems [25,29,30]. Their applications are closely related to cell imaging and DNA and protein sensing [31][32][33].Novel molecular construction of DR/NIR AIEgens can be achieved with electron donor (D) and electron acceptor (A) blocks connected through π-conjugated frameworks. The most fundamental phenomenon governing the spectroscopic properties is the intramolecular charge transfer (ICT) process from the donor to the acceptor in the excited state [34][35][36]. Intercrossed excited state between the low-lying local exciton (LE) and charge transfer (CT) exciton results from the D-A interaction. Obviously, the molecular geometry is crucial for the process.Benzodifuran derivatives have drawn attention for a wide range of biological and pharmacological applications, including antimicrobial, antiviral, analgesic and antitumor [37][38][39][40] activity. This class of heterocyclic compounds are also employed in dyes industry as pigments and in different fields of optoelectronics and photonics. Due to the excellent semiconducting properties [41,42], benzodifuran scaffolds are used as nonlinear optical materials [43], for dye sensitized solar cells [44] and in organic solar cell and transistors. Finally, as electron-rich building blocks they have a potential in the constructing of photoluminescent materials [45][46][47] Herein, we developed a new benzodifuran derivative from 2,6-diamino-4-(4-nitrophenyl) ...

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Spectroscopic studies of keto–enol tautomeric equilibrium of azo dyes

Abstract: Keto–enol tautomeric equilibrium of an azo dye is shifted to the keto form as the solvent polarity is increased.

Cited by 89 publications

References 32 publications

Synthesis, Solvatochromic Performance, pH Sensing, Dyeing Ability, and Antimicrobial Activity of Novel Hydrazone Dyestuffs

Synthesis, Solvatochromic Performance, pH Sensing, Dyeing Ability, and Antimicrobial Activity of Novel Hydrazone Dyestuffs

Isotopic splitting patterns in the ¹³C NMR spectra of some partially deuterated 1‐aryl‐2‐(phenyldiazenyl)butane‐1,3‐dione and 4‐hydroxy‐3‐(phenyldiazenyl)‐2H‐chromen‐2‐one: evidence for elucidation of tautomeric forms

A Novel DR/NIR T-Shaped AIEgen: Synthesis and X-Ray Crystal Structure Study

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Spectroscopic studies of keto–enol tautomeric equilibrium of azo dyes

Abstract: Keto–enol tautomeric equilibrium of an azo dye is shifted to the keto form as the solvent polarity is increased.

Cited by 89 publications

References 32 publications

Synthesis, Solvatochromic Performance, pH Sensing, Dyeing Ability, and Antimicrobial Activity of Novel Hydrazone Dyestuffs

Synthesis, Solvatochromic Performance, pH Sensing, Dyeing Ability, and Antimicrobial Activity of Novel Hydrazone Dyestuffs

Isotopic splitting patterns in the 13C NMR spectra of some partially deuterated 1‐aryl‐2‐(phenyldiazenyl)butane‐1,3‐dione and 4‐hydroxy‐3‐(phenyldiazenyl)‐2H‐chromen‐2‐one: evidence for elucidation of tautomeric forms

A Novel DR/NIR T-Shaped AIEgen: Synthesis and X-Ray Crystal Structure Study

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Isotopic splitting patterns in the ¹³C NMR spectra of some partially deuterated 1‐aryl‐2‐(phenyldiazenyl)butane‐1,3‐dione and 4‐hydroxy‐3‐(phenyldiazenyl)‐2H‐chromen‐2‐one: evidence for elucidation of tautomeric forms