Cyanine dyes of new heterocyclic ring systems: Synthesis and structure-spectra studies

New cyanine dyes including monomethine cyanine dyes (simple cyanine dyes) and trimethine cyanine dyes (carbocyanine dyes) incorporating benzo[2,3-b; 2′,3′-b′]bispyrazolo[4,5-b]-1,4-(oxa-, thia-, and pyra)-zine-6,12-dione were prepared. Structure-spectra studies were carried out via measuring the electronic visible absorption spectra of these dyes in 95% ethanol. Structural confirmations were determined through elemental analysis, IR, ¹H NMR spectroscopy and MS spectral data at the Micro Analytical Center, Cairo University.     

Cyanine dyes from polynitro- and poly(trifluoromethylsulphonyl)-benzenes

New monomethine and trimethine cyanine dyes with benzothiazole or indole and polynitro- or poly(trifluoromethylsulphonyl)-substituted benzene rings attached to the ends of the polymethine chain have been synthesised. Atoms of fluorine or methyl groups were introduced to the α-position of the polymethine chain. The influence of nitro and trifluoromethylsulphonyl groups on the colour of these dyes is compared. It is shown that the CF₃SO₂ group is a weaker auxochrome than the nitro group.     

Synthesis and antimicrobial activity of certain novel monomethine cyanine dyes

A series of novel monomethine cyanine dyes were synthesized by using 3-methyl-5-substituted-1-phenyl-pyrano[2,3-c]pyrazole derivatives 2a–c. Reaction of equimolar ratios of 2a–c with 2(4)-methyl heterocyclic quaternary salts afforded the corresponding monomethine cyanines 3a–c. Reaction of compound 5 with 2(4)-methyl heterocyclic quaternary salts gives monomethine 6a–c. Condensation reaction of equimolar ratios of compounds 7 and 9a,b with 2(4)-methyl heterocyclic quaternary salts afforded the corresponding monomethine cyanines 8a–c and 10a,b respectively. The new synthesized monomethine cyanine dyes were identified by elemental analyses, IR, ¹H-NMR and Ms spectral data. The electronic absorption spectra in ethanolic solution of novel monomethine cyanine dyes were measured and the antimicrobial activity of some selected monomethine cyanine dyes was discussed.     

Synthesis of novel tetracationic asymmetric monomeric monomethine cyanine dyes – highly fluorescent dsDNA probes

Quaternisation of monomethine cyanine dyes bearing haloalkyl chains, with the appropriate monoquaternised 1,4‐diazabicyclo[2.2.2]octane derivatives, yielded novel tetracationic asymmetric monomeric monomethine cyanine dyes belonging to the thiazole orange family. The optimal conditions for this reaction were investigated. The longest wavelength absorption maxima of the studied dyes are in the region 504–507 nm. The molar absorptivities of the target dyes are high, with values between 70 500 and 99 500 l mol^?1 cm^?1. The fluorescence intensity and the fluorescence quantum yields of the free dyes in solution or in the presence of double‐stranded DNA were determined using thiazole orange for comparison. The dyes are suitable for nucleic acid detection and have a high binding affinity, attributable to their four positive charges.     

Synthesis,absorption spectra studies,solvatochromism and halochromism of polymethine cyanine dyes

New polymethine cyanine dyes, including tetramethine and bis‐tetramethine cyanine dyes derived from benzo[2,3‐b;2′,3′‐b′]bis‐pyrazolo[4,5‐b]‐1,4‐(oxa‐, thia‐ and pyra‐)‐zine‐6,12‐dione, were synthesised. Absorption spectra for all the synthesised cyanine dyes were examined in 95% ethanol. The solvatochromism and halochromism for some selected dyes were investigated in pure solvents and in aqueous universal buffer solutions, respectively. Structural confirmations were carried out through elemental and spectroscopic analysis.     

Bright fluorescent dsDNA probes: novel polycationic asymmetric monomethine cyanine dyes based on thiazolopyridine‐quinolinium chromophore

Seven tri‐ and tetracationic monomeric and homodimeric monomethine cyanine dyes based on thiazolo[4,5‐b]pyridinium and quinolinium end groups were synthesised and characterised. The dyes were tested as fluorescent DNA intercalating probes to apply in DNA gel electrophoresis. The DNA samples stained with all dyes from the series demonstrated bright fluorescent signals. DNA fragments were successfully visualised under orange and green filters as well as under standard UV transillumination. Two of the studied dyes revealed higher sensitivity to DNA when compared with the commercial dimeric cyanine dye TOTO‐1. Their sensitivity reached that of the commercial dimeric cyanine dye YOYO‐1, but the emission was shifted to longer wavelengths. These qualities make the dyes suitable to apply in a wide range of medical and scientific analytical methods.     

Synthesis, spectral characterisation and anti-bacterial activity of various 1,3,4-oxadiazine cyanine dyes

A number of new styryl, aza-styryl, acyclic mero, cyclic mero and mixed cyanine dyes with a benzo[2,3- e ; 2',3'- e ']bis-1,3,4-oxadiazine nucleus were synthesised. The absorption spectra in the visible region of all the synthesised cyanine dyes in 95% ethanol solution were examined and studied in detail. Anti-bacterial activity for a number of selected dyes was evaluated against various bacterial strains. The structural determination was carried out using elemental and spectroscopic analysis.     

Synthesis and characterisation of monomethine cyanine dyes based on N-bridgehead heterocycles

In this paper, the synthesis and spectral properties of novel asymmetrical and symmetrical monomethine cyanine dyes are described. Reaction of phenylpyrazolones and oxazolones with acetyl thiourea and/or thiosemicarbazide afforded acetyl intermediate compounds which were then reacted with metal divalent chlorides, followed by reaction with N -methyl hetetrocyclic quaternary salts, to give asymmetrical monomethine cyanine dyes. Reaction of the 5-amino derivative of the intermediate compounds with acetaldehyde followed by reaction with N -methyl hetetrocyclic quaternary salts produced the symmetrical monomethine cyanine dyes. These new compounds were characterised with elemental analyses, visible absorption and infrared spectrometry, and ¹H/¹³C NMR and mass spectroscopy. The correlation between the colour and structure of these dyes was also investigated.     

Synthesis and colour spectroscopic investigation of some hemicyanine dyes

New hemicyanine dyes with a benzo[2,3‐b;2′,3′‐b′]bis‐furo[3,2‐d]pyrazolium nucleus were prepared. Spectroscopic investigations were carried out in 95% ethanol for all the synthesised cyanine dyes and/or in pure solvents which have different polarities for some selected dyes. Structural identification was carried out via elemental analysis, infra‐red and proton nuclear magnetic resonance spectral data.     

Synthesis and absorption spectra of some novel hetaryldisazocalix[4]arene derivatives

In this study, a convenient method for the synthesis of thirteen novel disazo dyes containing 25,26,27‐tribenzoyloxy‐28‐hydroxycalix[4]arene have been described. 5,11,17,23‐Tetra‐tert‐butyl‐25,26,27,28‐tetrahydroxycalix[4]arene, 25,26,27,28‐tetrahydroxycalix[4]arene and 25,26,27‐tribenzoyloxy‐28‐hydroxycalix[4]arene were synthesised based on previously published literature. 2‐Arylhdrazone‐3‐ketiminobutyronitriles were synthesised and reacted with hydrazine hydrate to afford the corresponding 5‐amino‐4‐arylazo‐3‐methyl‐1H‐pyrazoles. Thirteen novel hetaryldisazocalix[4]arene derivatives were achieved by diazotisation of 5‐amino‐4‐arylazo‐3‐methyl‐1H‐pyrazoles using nitrosylsulphuric acid, coupled with 25,26,27‐tribenzoyloxy‐28‐hydroxycalix[4]arene. The obtained hetaryldisazocalix[4]arene dyes were characterised based on Fourier Transform–infrared, proton nuclear magnetic resonance and mass spectroscopic techniques, as well as elemental analysis. The solvatochromic behaviour of these dyes in various solvents was examined. Acid‐base effects on the visible absorption maxima of the dyes were also reported.     

Dyes derived from benzo[a]phenoxazine – synthesis,spectroscopic properties,and potential application as sensors for l-cysteine

Several benzo[a]phenoxazine dyes containing a maleimide moiety have been synthesised and characterised by proton nuclear magnetic resonance spectroscopy and mass spectrometry. The spectroscopic properties, such as absorption and emission spectra, of these dyes – 9-maleimido-5H-benzo[a]phenoxazin-5-one ( 7a ), 6-chloro-9-maleimido-5H-benzo[a]phenoxazin-5-one ( 7b ), and 6-bromo-9-maleimido-5H-benzo[a]phenoxazin-5-one ( 7c ) – were examined. These compounds were evaluated as potential fluorescent and colorimetric probes for the detection of biothiols. Results show that the studied compounds exhibit colorimetric and fluorescent responses to l -cysteine at pH 7.4. In the presence of l -cysteine, the fluorescence intensity of synthesised dyes is greatly enhanced. The addition of l -cysteine to solutions of dyes 7a to 7c also results in red shifts of their absorption bands. The cytotoxic effect of tested dyes 7a to 7c against human neuroblastoma cells (SH-SY5Y) was determined by MTT assay. The fluorescent response of these compounds to thiols SH-SY5Y was examined. The results show that the tested compounds exhibit fluorescent response in this cell line, and the benzo[a]phenoxazine dyes substituted in the 6-position with a halogen ( 7b and 7c ) are less toxic against cells under experimental conditions than their unsubstituted analogue ( 7a ).     

Synthesis of azo benzo[b]thiophene derivatives and their application as disperse dyes

2-Amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile and ethyl-2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate were synthesised by reaction of cyclohexanone and sulphur with malononitrile and ethyl cyanoacetate respectively. These 2-aminothiophene derivatives were diazotised and coupled with a variety of coupling components to give azo dyes. The spectral properties of these dyes are reported. The dyes had generally good colouration and fastness properties on polyester.     

Dyes derived from 1,4‐naphthoquinone as initiators for radical and cationic photopolymerisation

Several 2‐phenylamino‐1,4‐naphthoquinone‐based dyes and two related benzo[2,3‐b]–phenazines were synthesised and characterised by proton nuclear magnetic resonance spectroscopy and electron ionisation mass spectrometry. The electrochemical and spectral properties of these compounds were investigated. The synthesised dyes were found to be capable photosensitisers for radical (reducible/oxidisable) and cationic polymerisations, respectively. In radical polymerization, better results in the oxidisable process were achieved.     

Monomethine cyanine dyes with an indole nucleus: Microwave-assisted solvent-free synthesis,spectral properties and theoretical studies

Four asymmetric monomethine indocyanine dyes were rapidly synthesized by the condensation of indole quaternary salts with 2-methylthio quinoline quaternary salt in the presence of triethylamine under solvent-free, microwave irradiation. The effects of microwave power and irradiation time on yield were examined. The products were identified using elemental analysis, IR, MS, UV–Vis spectra, ¹H and ¹³C NMR. The absorption of the dyes was investigated both experimentally and theoretically. Calculations performed using a combination of the time-dependent density functional theory (TD-DFT) and the polarizable continuum model (PCM) reproduced the π → π¹ type absorption bands of the dyes. Multiple linear regression, applied to the theoretical absorption maxima in different solvents, fitted well with experimental data. Resonance frequency calculations were undertaken to study the IR spectra of the dyes and the calculated results were in good accordance with experimental values.     

Synthesis and spectral properties of azohydroxypyridone disperse dyes containing a fluorosulphonyl group

A series of azohydroxypyridone disperse dyes containing fluorosulphonyl groups have been synthesised and their spectral properties were investigated. Azohydroxypyridone dyes, containing a nitro group instead of a fluorosulphonyl group para to the azo group in the diazo component, were also synthesised in order to compare spectral properties. The fluorosulphonyl substituted derivatives absorb maximally at shorter wavelengths and are tinctorially weaker than the nitroarylazopyridone dyes, although the former dyes have higher molar extinction coefficients. Also, the synthesised dyes exhibit positive solvatochromism so that the absorption bands of the dyes move toward longer wavelengths as the polarity of the solvent increases. Molecular computational methods provided reasonable predictions in the direction of solvatochromism for the dyes prepared.     

Reactions of aminoarylazopyrazoles with active methylene compounds. Part 1: Synthesis of 7-amino-3-arylazo-6-cyano-2-methylpyrazolo[5,1-c][1,2,4]triazines

In this study, 2-arylhydrazone-3-ketiminobutyronitriles were synthesised and reacted with hydrazine hydrate to afford 5-amino-4-arylazo-3-methyl-1 H -pyrazoles. These compounds were then diazotised and coupled with malononitrile to give pyrazolylazomalononitriles. Thirteen novel pyrazolo[5,1- c ][1,2,4]triazine dyes were synthesised by heating pyrazolylazomalononitriles in glacial acetic acid and characterised by elemental analysis and spectral methods. The effect of varying pH and solvent upon the absorption ability of the dyes substituted with electron-withdrawing and electron-donating groups at their o -, m - and p -position was examined in detail.     

Preparation of monomethine cyanine dyes as noncovalent labels for nucleic acids

By condensation of quaternary benzothiazolium, quinolinium and acridinium salts having an active methyl group with 1-(3-bromopropyl)-4-chloroquinolinium or 1-(3-bromo-2-hydroxypropyl)-4-chloroquinolinium salts in the presence of a basic agent such as triethylamine, 8 asymmetric and symmetric monomethine cyanine dyes bearing ω-bromopropyl substituent with one or two positive charges, were synthesized. Additionally, two of the dyes were quaternized with pyridine, and monomethine cyanines with two and three positive charges are prepared. Most of the dyes showed high molar absorptivity (70 000–100 000 l mol⁻¹ cm⁻¹). The acridinium dyes showed broad peaks with lower intensity of 30 000 l mol⁻¹ cm⁻¹. In the presence of nucleic acid in aqueous solutions, a strong enhancement of the fluorescence of these new dyes was observed.     

Synthesis and spectroscopic properties of novel azo dyes derived from phthalimide

A set of azo dyes has been synthesised using N -substituted phthalimides as diazo components. 3,5-Dibromo- N -substituted-phthalimidylazo derivatives were cyanated by cyanodehalogenation to give dicyano analogues. All of the synthesised intermediates and dyes have been characterised by mass spectrometry, ¹H-NMR or elemental analyses. The gamut of colour of the prepared dyes spanned much of the visible spectrum: absorption maxima of the dyes in formamide were observed in the range 436 to 609 nm. Consistent with results seen in previous studies of non-phthalimido monoazo disperse dyes, replacement of dibromo groups with dicyano functions in the phthalimide-based set led to large bathochromic shifts in absorption maxima, as did the introduction of acetylamino groups onto the coupler ring ortho to the azo link. However, switching an N -propyl function on the imido ring for a benzyl or 3-cyanopropyl substituent had little effect on absorption maxima. Good correlations between the observed absorption maxima of certain dyes and those of model analogues predicted by Pariser–Parr–Pople molecular orbital calculations were observed when steric effects were absent.     

Dyes derived from 3‐formyl‐2(1H)‐quinolone – synthesis,spectroscopic characterisation,and their behaviour in the presence of sulfhydryl and non‐sulfhydryl amino acids

Novel dyes based on a 3‐formyl‐2(1H)‐quinolone skeleton were synthesised and characterised using ¹H nuclear magnetic resonance spectroscopy and mass spectrometry. The spectroscopic properties of these dyes, such as their absorption spectra, emission spectra, and quantum fluorescence yields, were also examined. The behaviour of the obtained compounds at a pH of 7.4 in the absence and in the presence of thiol amino acids, such as l ‐cysteine, l ‐glutathione, and N‐acetyl‐l ‐cysteine, were studied. The spectroscopic responses of the tested dyes towards other amino acids were also investigated. A reference compound was synthesised to understand the reaction mechanism between the thiols and the obtained dyes. The experimental results show that the synthesised dyes have the potential to act as sensors for thiols.     

Preparation of thermally stable dyes derived from diketopyrrolopyrrole pigment by polymerisation with polyisocyanate binder

Four thermally stable and solvent soluble dyes were prepared from diketopyrrolopyrrole pigment via an N‐alkylation reaction. To improve the thermal stability of the dyes, a hydroxyl functional group that could react with blocked polyisocyanates was introduced into the dyes. The prepared dyes had absorption maxima near 500 nm, and the chromaticity diagrams of all synthesised dyes exhibited smaller x and y values than those of CI Pigment Red 254, indicating that the colour of the synthesised dyes was close to an orange shade. The dyes reacting with blocked polyisocyanates showed extremely high thermal stability compared with analogous dyes not reacting with polyisocyanates.