Pyrene-N,N-dimethylaniline heteroexcimer systems in aqueous micellar solutions

Strong quenching of fluoroscence of pyrene by N,N-dimethylaniline as well as N,N-dimethylaniline sulfonate has been observed in aqueous micellar solutions. Photoinduced electron transfer from the anilines to excited pyrene near the micelle-water interface has been demonstrated by means of laser photolysis studies.     

Excess enthalpies of binary solvent mixtures of 1-butanol and 2-methyl-2-propanol with aniline,N-methylaniline,and N,N-dimethylaniline

The excess molar enthalpies of binary solvent mixtures of 1-butanol and 2-methyl-2-propanol with aniline, N-methylaniline, and N,N-dimethylaniline were measured with a flow microcalorimeter at 40°C. The excess enthalpies are positive for all the systems, and smaller for the mixtures of 1-butanol than the corresponding mixtures of 2-methyl-2-propanol. With respect to the anilines, the values increase in the order aniline < N-methylaniline < N,N-dimethylaniline.     

Anisotropy of magnetic susceptibility and molar Cotton-Mouton constants of six anilines and 1,3,5-trimethylhexahydro-1,3,5-triazine

Conclusions The semiaxes of the magnetic susceptibility ellipsoid were determined for the Ph-N fragment in 4-substituted anilines and N,N-dimethylaniline. Deviations from additivity due to the additional paramagnetic contribution in a direction perpendicular to the plane of the aromatic ring were found.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2217–2221, October, 1987.     

HETEROEXCIMER SYSTEMS IN AQUEOUS MICELLAR SOLUTIONS

Fluorescence quenching due to charge transfer interactions in the excited state has been studied in aqueous micellar solutions. Fluorescers used were pyrene, various pyrene derivatives and several other conjugated π-electronic systems, and quenchers were N, N-dimethylaniline, N. N-dimethylaniline sulfonate, dicyanobenzenes and cyanopyridine. Strong quenching of the aromatic hydrocarbon fluorescence with dimethylanilines as well as dicyanobenzenes was observed, while no heteroexcimer emission was detected. The dependences of relative fluorescence yield and fluorescence decay curve upon the quencher concentration have been explained with equations derived on the basis of a simple model. Based on the obtained results, some discussions were given on the nature of micelle 'interior' and micelle 'surface'.     

Kinetics of Pyrene Fluorescence Quenching in the Presence of N,N-Dimethylaniline on the Surface of Titania Silica Colloids

A study was carried out on pyrene (Py) fluorescence quenching in the presence of N,N-dimethylaniline (DMA) on the surface of titania–silica colloids. Py fluorescence quenching is a function of the TiO₂ content in the binary colloids. The coadsorption of DMA molecules is accompanied by an increase in the Py fluorescence intensity due to the competitive adsorption of amine on the surface. Calculation of the formal kinetics of Py fluorescence quenching indicates the existence of two groups of sites differing in adsorption activity within each group.     

Features of diffusion-controlled bimolecular reaction of fluorescence quenching in sol-gel-xerogel transitions

Reaction kinetics have been investigated in the diffusion-controlled quenching of pyrene fluorescence by N,N-dimethylaniline in a medium that gradually changes from homogeneous to heterogeneous as a result of solution-sol-gel-xerogel transitions. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 122–125, March–April, 1998.     

Fluorescence quenching mechanisms of aromatic hydrocarbon-dicyanobenzene and-n.n-dimethylaniline systems in aqueous micellar solutions

Fluorescence quenching of pyrene and several other aromatic hydrocarbons by dicyanobenzenes as well as N,N-dimethylaniline has been observed in aqueous micellar solutions. The experimental results have been explained by means of equations for fluorescence intensity and decay curve derived on the basis of a simplified model.     

Thermometric titrations of amines with nitrosyl perchlorate in acetonitrile solvent

Thirteen aliphatic and four aromatic amines, namely diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri-n-butylamine, isopropylamine, di-isopropylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, aniline, N,N-dimethylaniline, 2-nitroaniline and 4-nitroaniline were titrated thermometrically with nitrosyl perchlorate in acetonitrile solvent. All the aliphatic amines gave very well-shaped thermometric titration curves. The calculated recovery values of the amines were very good. In comparison, the aromatic amines, aniline and N,N-dimethylaniline gave rather well-shaped titration curves, but the recovery values were fairly low. 2-Nitro- and 4-nitro anilines gave no thermometric response at all. The heats of reaction of the amines with nitrosyl perchlorate are rather high. However, the average heat of reaction of the aromatic amines is approximately two-thirds that of the average heat of the aliphatic amines. To support this method all the amines were also titrated potentiometrically and very similar results to those obtained with the thermometric method are seen. The nitrosyl ion is a Lewis acid, strong enough to titrate quantitatively aliphatic amines in acetonitrile solvent, but not strong enough to titrate aromatic amines at the required level in the same solvent.     

Transient processes of diffusion-controlled quenching of pyrene fluorescence on the surface of SiO2

Using the diffusion-controlled bimolecular reaction of quenching of pyrene fluorescence by N,N-dimethylaniline on the surface of thermally activated highly dispersed SiO₂ as an example it is shown that a transient non-steady-state process is observed in the initial section of the kinetics.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 6, pp. 328–331, November–December, 1994.     

Reactivity of aromatic amines with triplet 1,8-dihydroxyanthraquinone: a laser flash photolysis study

The property of the lowest excited triplet states of 1,8-dihydroxyanthraquinone (DHAQ) was investigated by using time-resolved laser flash photolysis at 355nm in organic solvents, i.e. acetonitrile and cyclohexane. The transient absorption spectra of the excited triplet DHAQ were obtained in acetonitrile, which have an absorption maximum at 480nm and two broad absorption bands around 350 and 650nm. 3DHAQ(*) is efficiently quenched by triphenylamine (TPA) via photoinduced electron transfer pathway, which was testified by the finding of TPA radical cation. In addition, aniline derivatives such as N,N-dimethylaniline (DMA), 3,5,N,N-tetramethylaniline (TMA), 4-dimethylaminobenzoic acid (DMABA) and dimethyl-p-toluidine (DMT) could also quench 3DHAQ(*) rapidly. Evidence for electron transfer interaction with anilines in acetonitrile was obtained from transient spectral characterization of formed radicals. Experimental k(q) values approach the diffusion-controlled rate limit, and decrease significantly from DMT (1.85x10(10)M-1s-1) to DMABA (1.95x10(9)M-1s-1). These k(q) values depend on the charge density on the "N" atom of anilines, which could be quantified by Hammett sigma constant.     

Spurious observation of the Marcus inverted region in bimolecular photoinduced electron transfer

The effect of viscosity on the bimolecular electron transfer quenching of a series of coumarins by N,N-dimethylaniline was investigated using steady-state and time-resolved fluorescence spectroscopy. The data reveal that the static and transient stages of the quenching become dominant as viscosity increases. When extracting the quenching rate constants using a simple Stern-Volmer analysis, a decrease of the rate constant with increasing driving force is observed above ~2 cP. However, this apparent Marcus inverted region, already reported several times with the same system in micelles and room temperature ionic liquids, totally vanishes when analyzing the data with a model accounting for the static and transient stages of the quenching. It appears that the apparent Marcus inverted region arises from the neglect of these quenching regimes together with the use of fluorophores with different excited-state lifetimes.     

ON THE MECHANISM OF QUENCHING OF SINGLET OXYGEN BY AMINES-III. EVIDENCE FOR A CHARGE-TRANSFER-LIKE COMPLEX

Abstract— A series of amines were found to quench singlet oxygen in the order tertiary > secondary > primary, with a reasonable correlation between the log of their rate constant of quenching and their ionization potential. In addition, a Hammett rho plot gave a rho value of - 1.39 for the quenching of singlet oxygen by a series of substituted N, N-dimethylanilines, in good agreement with the results obtained by a different method. It was found that some of the amines (anilines) quenched the triplet state of the dye-sensitizer (Rose Bengal) used for the production of singlet oxygen. Corrections in the results were made in the calculations of rates of quenching of singlet oxygen to allow for the triplet-state quenching. No extensive quenching of the singlet state of the dye was observed at the concentrations of the amines necessary for singlet-oxygen quenching. In one case (N, N, N', N'-tetramethylphenylenediamine) there was no observable chemical reaction between singlet oxygen and the amine. It was concluded that singlet oxygen undergoes physical quenching by the amines via partial charge-transfer intermediates.     

Photophysical processes of a fluorene derivative containing 1,3,4-oxadiazole

The photophysical processes of 9,9-bis[4'-[2'-phenyl-5'-(3'-(methacryl-amido)phenyl)]-1',3',4'-oxadiazolylphenyl]fluorene (F-MAOP) formed by Heck reaction of 9,9-bis(4'-iodophenyl)fluorene (F-IP) and 2-phenyl-5-[3'-(methacrylamido)phenyl]-1,3,4-oxadiazole (OXD) have been carefully studied. The results show that the compound emits blue and blue-violet light and the emission spectra exhibit obvious solvent effect. With the increase of polarity of solvents, the fluorescence spectra change obviously and appear blue shift at room temperature. In addition, the light-emitting can be quenched by both electron donor (N,N-dimethylaniline, DMA) and electron acceptor (C60). When N,N-dimethylaniline is gradually added into the solution of F-MAOP, the emission intensities of fluorescence are unusually increased. But when the concentration of DMA beyond a certain scope, the emission intensities of fluorescence are gradually decreased. The dimolecular exciplex between F-MAOP and C60 are formed and the quenching effect follows the Stern-Volmer equation. Moreover, interaction between F-MAOP and carbon nanotubes (CNTs) is also studied by fluorescent quenching.     

Investigation of the structure of the adsorption layer of nonionic surfactant TX-100 and of the pyrogenic dispersive silica surface genesis using the phototransfer reaction

The influence of a silica (aerosil) surface on the reaction kinetics of a photoinduced electron transfer and quenching of fluoresence of pyrene (Py) in the presence of N,N-dimethylaniline (DMA) when adsorbed from hexane has been studied. A photoreaction between Py and DMA is observed; over a wide range the quenching of the Py fluorescence obeys a Stern-Volmer equation mainly. When Py and DMA are solubilized in aqueous micelles of TX-100 and then adsorbed on an aerosil surface, the influence of the surface on the photoreaction kinetics is negligible. Removal of water from the above system leads to the suppression of the photoreaction. The apparently abnormally long lifetime of Py may be explained by a rearrangement of an adsorption layer, micelle degradation, and encapsulation of the fluorophore.     

Photoinduced electron transfer from N,N-dimethylaniline to 7-amino coumarins in protein-surfactant complex: slowing down of electron transfer dynamics compared to micelles

Photoinduced electron transfer from N,N-dimethylaniline to different Coumarin dyes has been investigated in dodecyl trimethyl ammonium bromide (DTAB) micelles and in Bovine serum albumin (BSA)-DTAB protein-surfactant complex using steady-state and picosecond time-resolved fluorescence spectroscopy. We observed a slower fluorescence quenching rate in the DTAB micelles and in the protein-surfactant complex as compared to that in pure acetonitrile solution. Moreover, the observed fluorescence quenching in BSA-DTAB complex was found to be slower than that in DTAB micelles. In the correlation of free-energy change with the fluorescence quenching constant we observed a deviation in the fluorescence quenching electron transfer rate for Coumarin 151 (C-151) from the normal Marcus curve. This observation is ascribed to the stronger interaction of C-151 with the surfactant molecules present in the micelles. This is evident from the slower translation diffusion (D(L)) of Coumarin 151 compared to other probe molecules.     

Characteristics of the kinetics of exciplex formation between pyrene and N,N-dimethylaniline on a porous silica surface

The bimolecular photochemical quenching of the fluorescence of pyrene by N,N-dimethylaniline on the surface of various porous silicas with low coverage of the surface (less than a monolayer) has been studied. The kinetics of this process on porous and nonporous silica have been compared. Institute of Surface Chemistry, National Academy of Sciences of Ukraine, 31 Prosp. Nauki, 252039, Kiev. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 188–191, May–June, 1997.     

p-toluene sulfonic acid-promoted rapid and facile baeyer condensation with microwave irradiation under solvent-free conditions

A fast and efficient method has been developed for the synthesis of triarylmethanes catalyzed by p-TsOH under microwave irradiation. The reactions of different aryl aldehydes carrying activated and deactivated groups with N,N-dimethylaniline in the presence of a catalytic amount of p-TsOH produced the corresponding triarylmethanes in good to excellent yields.     

One-pot facile synthesis of acridine derivatives under solvent-free condition

N,N’-Dibromo-N,N’-1,2-ethanediylbis(p-toluenesulfonamide) [BNBTS] as a reusable catalyst promoted one-pot synthesis of benzo[c]acridines in good to high yields under three-component reaction from anilines, aldehydes and cyclic 1,3-dicarbonyl compounds under solvent-free conditions.     

Room temperature solution studies of complexation between o-chloranil and a series of anilines by spectrophotometric method.

Electron donor-acceptor (EDA) complex formation between o-chloranil and a series of anilines has been studied in CCl4 medium. In all the cases, EDA complexes are formed instantaneously on mixing the donor and acceptor solutions. N,N-dimethylaniline and N,N-dimethyl-p-toluidine form stable EDA complexes with o-chloranil while the other complexes decay slowly into secondary products. The kinetics of all these reactions has been studied by UV-VIS absorption spectrophotometric method and the rate constants of the reactions and formation constants of the EDA complexes have been determined. The charge transfer (CT) transition energies of the complexes are found to change systematically with change in the number and position of the methyl groups in the donor molecules (methylanilines). From an analysis of this variation, the electron affinity of o-chloranil has been found to be 2.54 eV. A perturbational inductive effect Hückel parameter hMe has been found from this trend and the value obtained (-0.27) is very close to that (-0.3) obtained by Lepley (J. Am. Chem. Soc., 86 (1964) 2545) from a study of tetracyano ethylene (TCNE)-methylbenzene complexes.     

Anomalous association and fluorophore influence on the position of dimethylaniline in micelles: fluorescence quenching of 1,8-acridinedione

Fluorescence quenching of 9,10-dimethyl-3, 4,6,7,9,10-hexahydro-1,8(2H,5H) acridinedione (ADD) dye by N,N-dimethylaniline (DMA) in SDS and CTAB were studied by steady state fluorescence and time resolved techniques. The Stern-Volmer plots for the quenching of ADD by DMA is found to be linear and the Stern-Volmer constant K(SV) depends on the micellar concentration. The fluorescence quenching analysis reveals the binding of DMA with the micelles. The perturbation of the probe on the position of DMA molecule in micelle is inferred in the present investigation. The ADD fluorophore drives the DMA molecule into the non-polar region (core) of the micelle whereas other fluorophores like pyrene and rhodamine6G do not affect the position of DMA. In this report, the importance of the nature of fluorophores in determining the position and association of the quencher molecules in the aggregated systems is being discussed.