Near-infrared solid-state fluorescent naphthooxazine dyes attached with bulky dibutylamino and perfluoroalkenyloxy groups at 6- and 9-positions

No solid-state fluorescence is observed for 9-(diethylamino)benzo[a]phenoxazin-5-one (Nile Red). However, 9-dibutylamino-6-{perfluoro[4-methyl-3-(1-methylethyl)-2-penten]-2-oxy}benzo[a]phenoxazin-5-one showed fluorescence maximum at 717 nm in solid state with fluorescence quantum yield 0.024. X-ray crystallographic analysis suggests that prevention of network π−π interactions by the bulky fluorine-containing and dibutylamino groups is essential to show solid-state fluorescence.     

Fluorescence determination of steroidal dienones

Reaction of Δ^1,4-3-keto steroids with zinc and acid produces a characteristic fluorescence. Estrogenic, 3-keto and Δ⁴-3-keto steroids did not yield this fluorescence. Stabilization of the dienone fluorescence by extraction into butyl ether allowed quantitation of triamcinolone acetonide in liquid formulations in which this dienone was present at the 0.01% level. A mechanism for the reaction is proposed.     

Absorption and fluorescence spectroscopic characterisation of a phenothiazine–flavin dyad

The phenothiazine–phenylene–isoalloxazine dyad, 3-methyl-10-[4-(10-heptyl-10H-phenothiazin-3-yl)-phenyl]-10H-benzo[g]pteridine-2,4-dione, dissolved in either dichloromethane or acetonitrile is characterized by absorption and emission spectroscopy. Absorption cross-section spectra, stimulated emission cross-section spectra, fluorescence quantum distributions, fluorescence quantum yields, and degrees of fluorescence polarisation are determined. The fluorescence decay is determined by time-resolved measurements. The dye photo-stability is investigated by observation of absorption spectral changes due to prolonged blue-light excitation. The absorption spectrum of the dyad resembles the superposition of the absorption of the isoalloxazine (flavin) moiety and of the phenylphenothiazine moiety. Photo-excitation of the flavin moiety causes fluorescence quenching by ground-state reductive electron transfer from phenylphenothiazine to isoalloxazine followed by charge recombination. Photo-excitation of the phenothiazine moiety causes (i) efficient excited-state oxidative electron transfer from phenothiazine to isoalloxazine with successive recombination, and (ii) moderate energy transfer followed by ground-state phenothiazine electron transfer and recombination.     

Two-photon induced fluorescence of novel dyes

Three novel compounds, trans-2-[p-(N-ethyl-N-(hydroxyethyl)amino)styryl]-N-methylbenzothiazolium iodide (1), trans-2-[p-(N-ethyl-N-(hydroxyethyl)amino)styryl]-1′,3′,3′-trimethylindolium iodide (2), and trans-2-[p-(N,N-dimethylamino)styryl]-1′,3′,3′-trimethylindolium iodide (3), were synthesized and their two-photon induced fluorescence behavior was studied. Under excitation by 1064 nm laser irradiation, the solutions of these compounds exhibit two-photon induced fluorescence with λ_max at 639, 666 and 665 nm for 1, 2 and 3 respectively.     

Spectral characterisation of new organic fluorescent dyes with an alkoxysilane moiety and their utilisation for the labelling of layered silicates

New fluorescence dyes with an alkoxysilane moiety were synthesised by the condensation of 3-(triethoxysilyl)-1-propanamine (3-aminopropyltriethoxysilane) with 4,10-benzothioxanthene-3,1′-dicarboxylic acid anhydride (BTXA) and N,N-dimethylaminonaphthalene-1,8-dicarboxylic acid anhydride (DMANA), which was accompanied by the formation of an imidic bridge. The compounds N-(3-(triethoxysilyl)propyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTX-S) and 4-(N′, N′-dimethyl)-N-(triethoxysilyl)propyl-1,8-naphthalene dicarboxylic acid imide (DMAN-S) were characterised by steady-state and time-resolved fluorescence spectroscopy in chloroform and ethanol. Both conjugates (BTX-S and DMAN-S) exhibited absorption and emission bands in the same region as the un-substituted BTXA and DMANA. An important Stokes shift was observed for DMAN-S in ethanol. A high fluorescence quantum yield was observed for BTX-S in both solvents and for DMAN-S in chloroform. In addition, the newly developed fluorescent silane dyes were covalently attached to the microscopic particles of layered silicates and on the surface of SiO₂ wafers as a proof of concept for fluorescence particle (surface) visualisation. The surface wafer modification was precisely characterised by X-ray photoelectron spectroscopy (XPS). Successful covalent linkage onto the particles of layered silicates was proved by confocal laser scanning microscopy technique.     

Synthesis and photochromic and fluorescence properties of 3-(1-benzyl-5-methoxy-2-methylindolyl)-4-thienyl-substituted furan(pyrrole)-2,5-diones

New nonsymmetrical dihetarylethenes, 3-(1-benzyl-5-methoxy-2-methyl-1H-indol-3-yl)-4-(3-thienyl)furan-2,5-dione and 1-alkyl- and (1-aryl)-3-(1-benzyl-5-methoxy-2-methyl-1H-indol-3-yl)-4-(3-thienyl)-1H-pyrrole-2,5-dione, exhibiting photochromic properties in solutions were synthesized. Noncyclic isomers of dihetarylethenes show fluorescence with quantum yields up to 0.13.     

Fluorescence properties of some 2-(4-amino-substituted-3-nitrophenyl)-3-hydroxyquinolin-4(1H)-ones

2-(4-Amino-substituted-3-nitrophenyl)-3-hydroxyquinolin-4(1H)-ones have been studied to evaluate their fluorescence properties and possible use as molecular fluorescent probes. The amino group was substituted with various alkyl moieties possessing a suitable terminal functional group (such as hydroxy or amino group) that could serve to bind a 3-hydroxyquinolin-4(1H)-one (3HQ) fluorescence label to a biomolecule. Besides simple hydrocarbon chains, ligands containing ethylenoxy units as optimal spacers were also tested. The structure-fluorescence properties and theoretical applicability of the studied molecules are discussed.     

Synthesis and photochromic properties of new nonsymmetric dihetarylethenes ?? indole and thiophene derivatives

New nonsymmetric dihetarylethenes were synthesized: 3-(5-methoxy-1,2-dimethyl-1H-indol-3-yl)-4-(3-thienyl)furan-2,5-dione and photochromic 1-alkyl-(1-aryl)-3-(5-methoxy-1,2-dimethyl-1H-indol-3-yl)-4-(3-thienyl)-1(H)-pyrrole-2,5-diones. The absence of benzoannulation in the indole moiety results in the enhancement of the efficiencies of fluorescence and photocyclization of noncyclic isomers compared to the benzoindole derivatives.     

Synthesis and photoluminescent properties of 7-N,N-diphenylamino-3- benzoheterocyclic coumarin derivatives

Two new 7-N,N-diphenylamino-3-benzoheterocyclic coumarin derivatives containing electron-transporting benzotriazolyl or benzoxazolyl moiety, 3-(1-benzotriazole)-7-N,N-diphenylaminocoumarin (BTDC) and 3-(2-benzoxazole)-7-N,N-diphenylaminocoumarin (BODC), were synthesized and characterized by element analysis, ¹H NMR and FT-IR spectra. The UV–vis and fluorescence spectra of these coumarin derivatives were investigated. The results show that BTDC and BODC exhibit strong blue and red emissions, respectively, under ultraviolet light excitation. The relationships between the chemical structure and the fluorescence characteristics of the 7-N,N-diphenylamino-3-benzoheterocyclic coumarin derivatives are discussed. It was found that the coumarin derivative will become a high-efficiency emitting material when an amino group is attached in 7-position of the coumarin ring, and 7- strong electron donors can improve the ability of the intramolecular charge transfer of the coumarin molecules.     

Anthracene-9-methanol—a novel fluorescent phototrigger for biomolecular caging

Photoexcitation of a solution of anthracene-9-methanol derived esters at ∼386 nm in CH₃CN/H₂O (3:2 v/v) results in fluorescence emission in the 380-480 nm range, with quantum yields of fluorescence (Φ_f) in the 0.01-0.09 range and releases of the carboxylic acids in good chemical yields (43-100%), with quantum yields of photoreaction (Φ_PR, i.e., the photodisappearance of the esters) in the 0.067-0.426 range.     

Thermo-reversibility of the fluorescence enhancement of acridine orange induced by supramolecular self-assembly

Fluorescence enhancement of acridine orange (AO) in supramolecular hydrogels formed by self-assembly of the gelators 3-{[(2R)-2-(octadecylamino)-3-phenylpropanoyl]amino}butyrate (TC₁₈PheBu) and 1,3:2,4-di-O-benzylidene-d-sorbitol (DBS) was investigated by steady-state and varying temperature fluorescence, polarized fluorescence and time-resolved fluorescence techniques. The results showed that the fluorescence intensities of AO in the gels remarkably increased in comparison with AO aqueous solutions, and increased with an increase of the gelator concentrations. The varying temperature fluorescence analysis indicated that fluorescence intensities of AO in the gels decreased upon an increase of temperature, and vice versa. This can be attributed to aggregation and dissociation of the gelators in the systems, since the fluorescence enhancement of AO was induced by self-assembly of the gelators. Polarized fluorescence analysis indicated that the values of anisotropy (r) of AO are significantly higher than that in water. This further confirmed that the three-dimensional network formed by the gelator aggregates constrained the rotation of AO entrapped within the gels, resulting in high values of anisotropy. Time-resolved fluorescence analysis indicated that the rates of fluorescence decay in the gels are lower than that in water. These results reveal thermo-reversibility of the fluorescence enhancement of AO in supramolecular hydrogels.     

Structure and condensation reactions of 2,3-dihydrofuro[3,2-c]coumarin-3-one

2,3-Dihydrofuro[3,2-c]coumarin-3-one was synthesized in quantitative yield from 3-(??-bromoacetyl)-4-hydroxycoumarin in the presence of nucleophiles (including solvents). This compound undergoes keto-enol tautomerization and easily reacts with aromatic and heteroaromatic aldehydes to form crotonization products having a Z configuration and exhibiting strong fluorescence.     

Dual-sensitive probe 1-imidazole-2-(5-benzoacridine)-ethanone for the determination of amines in environmental water using HPLC with fluorescence detection and online atmospheric chemical ionization-mass spectrometry identification

Dual-sensitive probe of 1-imidazole-2-(5-benzoacridine)-ethanone (IBAE) for the determination of free amines with fluorescence detection and online highly sensitive atmospheric chemical ionization-mass spectrometry identification (APCI-MS) has been developed. 2-(Benzoacridine)-5-acetic acid (BAAA) reacts with coupling agent N,N′-carbonyldiimidazole (CDI) to form a highly activated amide intermediate 1-imidazole-2-(5-benzoacridine)-ethanone (IBAE), which is dual-sensitive probe. The amide intermediate (IBAE) reacts preferably with amines in dimethylformamide (DMF) solvent to give the high yields of derivatives. IBAE-amine derivatives are not only sensitive to fluorescence but also to MS ionizable efficiency. The percent ionization δ values change from 0 to 57.32% in aqueous acetonitrile and from 0 to 62.14% in aqueous methanol. The relative standard deviations of the peak areas with fluorescence detection for each amine are <1.24% (40 ng/ml, n = 6). The fluorescence detection limits (at a signal-to-noise ratio of 3) are in the range of 0.15-0.50 ng/ml. The online APCI-MS detection limits are in the range of 2.07-8.51 ng/ml (at a signal-to-noise ratio of 3). Therefore, the facile IBAE intermediate derivatization allowed the development of a highly sensitive and specific method for the quantitative analysis of trace levels of amines in environmental water.     

A ‘turn-on’ fluorescent chemosensor based on rhodamine-N-(3-aminopropyl)-imidazole for detection of Al ions

A novel N-(3-aminopropyl)-imidazole-appended rhodamine-based fluorescent chemosensor was synthesized. The sensing behavior and selectivity of the synthesized chemosensor toward metal cations were studied by UV/vis and fluorescence spectroscopy. The chemosensor recognized Al³⁺ ions by a significantly enhanced fluorescence and a visible color change due to opening of the spirolactam ring triggered by the addition of Al³⁺ ions.     

Multi-carbazole derivatives for two-photon absorption data storage: Synthesis, optical properties and theoretical calculation

Two novel quadrupolar organic compounds, 3-(4-((E)-2-(9-butyl-9H-carbazol-6-yl) vinyl)styryl)-9-propyl-9H-carbazole (BCSPC) and 3-(3-(3-((1E)-2-(4-((E)-2-(3-(3,5-bis(9-butyl-9H-carbazol-6-yl)phenyl)-9-butyl-9H-carbazol-6-yl)vinyl)phenyl) vinyl)-9-butyl-9H-carbazol-6-yl)-5-(9-butyl-9H-carbazol-6-yl)phenyl)-9-butyl-9H-carbazole (BCPBC), with different conjugated arms, have been designed and synthesized. Their one- and two-photon absorption (TPA) and excited fluorescence properties have been experimentally investigated. The two-photon absorption cross-sections of two compounds were estimated by two-photon excited fluorescence technique using 200 fs, 76 MHz, Ti:sapphire laser, which are 22 and 154 GM for BCSPC and BCPBC, respectively. The optimal excitation wavelengths are 780 nm for both BCSPC and BCPBC. A data recording experiment proved the potential application of the materials.     

Novel asymmetric dihetarylethenes derived from N-isopropylindole and thiophene: synthesis and photochromic properties

Novel asymmetric dihetarylethenes, viz., 3-(1-isopropyl-5-methoxy-2-methyl-1H-indol-3-yl)-4-(3-thienyl)furan-2,5-dione and 1-alkyl/aryl-3-(1-isopropyl-5-methoxy-2-methyl-1H-indol-3-yl)-4-(3-thienyl)-1H-pyrrole-2,5-diones, were obtained. These dihetarylethenes exhibit photochromism in solutions. Replacement of the N-methyl group in the indole fragment by the N-isopropyl group imparts photochromic properties to the resulting furan-2,5-dione derivative. The open forms of (N-isopropylindol-3-yl)pyrrole-2,5-diones are characterized by lower quantum yields of fluorescence, and their cyclic forms are thermally more stable.     

A new fluorescent-colorimetric chemosensor for fluoride anion based on benzimidazolium salt

Two new benzimidazolium salts with the same cationic moiety and different anions 3-(2′-((8″-hydroxy-9″,10″-dioxo-9″,10″-dihydroanthracen-1″-yl)oxy)ethyl)-1-(pyridin-2?-ylmethyl)-1H-benzo[d]imidazol-3-ium bromide and 3-(2′-((8″-hydroxy-9″,10″-dioxo-9″,10″-dihydroanthracen-1″-yl)oxy)ethyl)-1-(pyridin-2?-ylmethyl)-1H-benzo[d]imidazol-3-ium hexafluorophosphate were prepared and characterized. The single crystal structure of 3-(2′-((8″-hydroxy-9″,10″-dioxo-9″,10″-dihydroanthracen-1″-yl)oxy)ethyl)-1-(pyridin-2?-ylmethyl)-1H-benzo[d]imidazol-3-ium bromide was determined by X-ray single crystal diffraction. Particularly, anion recognition using 3-(2′-((8″-hydroxy-9″,10″-dioxo-9″,10″-dihydroanthracen-1″-yl)oxy)ethyl)-1-(pyridin-2?-ylmethyl)-1H-benzo[d]imidazol-3-ium hexafluorophosphate as a chemosensor was carried out via fluorescence and ultraviolet spectroscopy, ¹H NMR titrations, HRMS and IR spectra. The response of this chemosensor to fluoride anion can be observed through both remarkable fluorescence quenching and color change under visible light (from orange to purple). The results indicated that this chemosensor can distinguish fluoride anion from other anions via the instrument and naked eyes, and this is greatly convenient in practical operation.     

New photochromic symmetrical and unsymmetrical bis(heteroaryl)maleimides: A spectrokinetic study

The photochromic behavior of two newly synthesized diarylethenes is here presented. The compounds studied are the symmetrical (1-benzyl-3,4-bis(2-methylbenzo[b]thiophen-3-yl)-[1H]-2,5-dihydropyrrol-2,5-dione) and the unsymmetrical (1-benzyl-3-(2-methylbenzo[b]thiophen-3-yl)-4-(2,5-dimethyl-3-thienyl)-[1H]-2,5-dihydropyrrol-2,5-dione). Upon stimulation with UV or violet light, these compounds become red-colored due to photocyclization and cyclorevert to the light yellow open form upon irradiation with visible light. In this work, absorption and fluorescence spectra, molar absorption coefficients of the ethenic and cyclized forms, fluorescence quantum yields and photochemical quantum yields of both the forward and back photoreactions were determined. Temperature, excitation wavelength and solvent effects were explored. The symmetrical compound was found to be a bistable photochrome. In contrast, the unsymmetrical molecule resulted unsuitable as photochrome because of side degradation processes occurring in competition with cyclization.     

Synthesis,crystal structures and photoluminescence of 7-(N,N′-diethylamino)-3-phenylcoumarin derivatives

Two new coumarin derivatives, 7-(N,N′-diethylamino)-3-(4-hydroxyphenyl)-coumarin and 7-(N,N′-diethylamino)-3-(4-bromophenyl)-coumarin, were synthesized successfully. Their structures were verified by single crystal X-ray crystallography. The UV–vis absorption and fluorescence of the compounds were discussed. The compounds exhibit strong blue emission under ultraviolet light excitation. The molecular structures, the lowest energy transitions and the UV–vis spectra of 7-(N,N′-diethylamino)-3-(4-hydroxyphenyl)-coumarin and 7-(N,N′-diethylamino)-3-(4-bromophenyl)-coumarin have been studied with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at B3LYP/6-31G(d) level.     

Selective formation of luminescent chiral cocrystal: Molecular self-assembly of 2,2′-binaphthol and 2-(3-pyridyl)-1H-benzimidazole

Luminescent chiral cocrystal based on the self-assembly of 2,2'-binaphthol and 2-(3-pyridyl)-1H-benzimidazole (P.) has been developed, in which 100% R configuration of BINOL can be obtained in the cocrystal products. The final structure presents the same P.R. The studies suggested that the cocrystallization approach could have much flexibility and potential applications for the design of chiral fluorescent materials.