Reichardt's Dye Research Articles

Solvation Environment Provided by Self‐Assembling Aqueous Sodium Oleate+1‐Octanol Small Unilamellar Vesicles

Self‐assembling vesicles composed of aqueous sodium oleate and 1‐octanol are prepared by simple mixing and analyzed with fluorescence probes pyrene, 1,3‐bis(1‐pyrenyl)propane, Nile Red, dansylamide, and 1‐pyrenecarboxaldehyde, and absorbance probe Reichardt's betaine dye. Reichardt's dye locates itself in the interfacial region of the vesicles. In that cybotactic region it reports a solvation environment similar to ethanol. Pyrene locates deeper to the center of the lipid bilayer in an extremely nonpolar environment. 1‐Pyrenecarboxaldehyde resides in the stable interfacial region and reports a static dielectric constant comparable to that of ethanol. 1,3‐Bis(1‐pyrenyl)propane indicates an extremely high microviscosity in the cybotactic region of the probe. Nile Red initially shows a variable Stokes shift, but eventually locates in the interfacial region and exhibits a microenvironment similar to a short‐chain alcohol. Dansylamide shows similar results. A comparison with micellar aqueous sodium dodecylsulfate indicates that the solvation microenvironment afforded by these novel self‐assembling vesicles is significantly less dipolar and more viscous.

Solvatochromism of a Novel Betaine Dye Derived from Purine

A novel solvatochromic betaine dye has been synthesized from xanthosine and characterized spectroscopically by UV-vis in a broad range of solvents. The dye 9-(2',3',5'-tri-O-acetyl-beta-d-ribofuranosyl)-2-(pyridinium-1-yl)-9H-purin-6-olate, 1a, exhibits solvent-induced spectral band shifts that are (2)/(3) as large as that of the betaine known as Reichardt's dye, which forms the basis of the E(T)(30) solvent polarity scale. Moreover, the dye 1a is a ribonucleoside and hence has the potential application as a polarity probe for application in RNA oligonucleotides. The isomeric dye 6-(pyridinium-1)-yl-9H-purin-2-olate, 2a, has also been synthesized and exhibits slightly smaller solvatochromic band shifts. The new betaine dyes have also been studied by comparing the experimental and calculated solvatochromic shifts based on the calculation of the UV/vis absorption spectra, using a combination of methods with density functional theory (DFT). The COSMO continuum dielectric method, an applied electric field term in the Hamiltonian, and time-dependent density functional theory (TD-DFT) methods were used to obtain absorption energies, ground-state dipole moments, and the difference dipole moment between the ground and excited states. The calculations predict a lower energy absorption band of charge-transfer character that is highly solvatochromic, and a higher energy absorption band that has pi-pi character which is not solvatochromic, in agreement with the experimental data. For Reichardt's dye the difference dipole moment between the ground and excited state (Deltamu = mu(e) - mu(g)) was also calculated and compared to experiment: Deltamu(calcd) = -6 D and Deltamu(exptl) = -9 +/- 1 D.(1) The ground-state dipole moment was found to be mu(g)(calcd) = 18 D and mu(g)(exptl) = 14.8 +/- 1.2 D.(1).

Dendritic supramolecular assemblies for drug delivery

Dendritic supramolecular assemblies were formed in water with Reichardt's dye or the anticancer drug 10-hydroxycamptothecin and the dendritic macromolecule, ([G4]-PGLSA-OH)2-PEG3400.

Thermoresponsive micelles from well-defined block copolymers synthesized via reversible addition-fragmentation chain transfer polymerization

Poly(N-isopropylacrylamide) (PNIPAAm) homopolymers synthesized by reversible addition–fragmentation chain transfer polymerization were used as macro-chain-transfer agents to synthesize smart amphiphilic block copolymers with a switchable hydrophilic–hydrophobic block of PNIPAAm and a hydrophilic block of poly(N-dimethylacrylamide). All polymers were characterized by gel permeation chromatography, 1H NMR, and differential scanning calorimetry. The reversible micelles formed by the block copolymers of various compositions in aqueous solutions were characterized by 1H NMR, dynamic light scattering, and tensiometry. Micelles were observed in the aqueous solutions when the temperature was increased to 40 °C because of the collapse of the PNIPAAm structure, which led to a PNIPAAm hydrophobic block. The drug loading capacity was illustrated with the use of the solvatochromic Reichardt's dye and measured by ultraviolet–visible. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3643–3654, 2005

Mechanism of the Optical Response of Mesoporous Silica Impregnated with Reichardt's Dye to NH3 and Other Gases

Neutral amines-templated mesoporous silica systems impregnated with Reichardt's dye are pink in color if previously dehydrated and white if still covered with hydroxyls: the pink coloration is, however, reversibly restored by exposing the latter sample only to NH3 and amines. The mechanism of color change is discussed, and such systems are proposed as possible ammonia gas sensors.

Characterization of Lactam-Containing Binary Solvents by Solvatochromic Indicators

Preferential solvation and intermolecular interactions of the solvatochromic indicators 4-nitroanisole, 4-nitroaniline, 4-nitrophenol, and Reichardt's dye is studied at 298.15 K in the binary solvents 2-pyrrolidinone/water, N-methylpyrrolidinone/water, and 2-pyrrolidinone/N-methylpyrrolidinone. From the experimental data the Reichardt's and Kamlet−Taft parameters were evaluated for the mixed solvents. A preferential solvation model was applied to analyze the solvation effect of the indicator by the different solvents used, and from these data useful information about solute−solvent and solvent−solvent interactions was deduced. Comparison with other thermophysical data reveals a relationship between the solvatochromic parameters and the partial molar volumes, mainly in water-containing solvents.

Mesostructured SBA-3 silica containing Reichardt's dye as an optical ammonia sensor

Mesostructured SBA-3 silica containing Reichardt's dye is shown to give a reversible optical response to gaseous ammonia, with a response time of a few seconds and an intensity proportional to the ammonia partial pressure, which are desirable properties for gas sensing.

Solvent strength of ionic liquid/CO2 mixtures

Previously we have shown that organic solutes can be extracted from ionic liquids (ILs) with supercritical CO2 and that ILs can be induced to separate from organic and aqueous mixtures by applying gaseous CO2 pressure. Thus, we are interested in the solvent strength of IL/CO2 mixtures. Here we use 4-nitroaniline, N,N-diethyl-4-nitroaniline and Reichardt's dye 33 to determine the Kamlet–Taft parameters for four different imidazolium based ILs and their mixtures with CO2 at 25 and 40 °C. The effect of temperature and carbon dioxide concentration on these parameters was determined. The polarizability parameter depends weakly on the CO2 concentration. However, the hydrogen bond donating ability and the hydrogen bond accepting ability are virtually independent of CO2 pressure. The results indicate that the strong interactions between ILs and probe molecules are not influenced by CO2.

Dendritic molecular capsules for hydrophobic compounds.

Reichardt's dye, a highly solvatochromic dye, was encapsulated within poly (glycerol succinic acid) ([Gn]-PGLSA-OH) dendrimers to investigate the interior environment of these dendritic macromolecules. The absorption maximum for the encapsulated Reichardt's dye in water was indicative of a relatively high dielectric constant present within the dye/dendrimer complex. (1)H NMR of the encapsulated complex showed the presence of aromatic protons from Reichardt's dye along with the aliphatic protons of the dendrimer. Additionally, there were substantial changes in T(1) and T(2) times of the encapsulated dye when compared with the free dye, and (1)H NOESY spectra for the complex showed a significant number of intermolecular NOE cross-peaks. These data reveal the close through-space proximity of the dye to the dendrimer and the restricted motion of the encapsulated dye. To demonstrate the potential use of these macromolecules as drug delivery vehicles, the poorly water-soluble anticancer drug 10-hydroxycamptothecin (10HCPT) was encapsulated within a carboxylated PGLSA dendrimer ([G4]-PGLSA-COONa). Cytotoxicity assays with human breast cancer cells showed a significant reduction of cell viability, demonstrating that 10HCPT retains activity upon encapsulation.

Empirical Polarity Parameters of Celluloses and Related Materials

Kamlet–Taft's α (hydrogen-bond donating (HBD) ability), β (hydrogen-bond accepting (HBA) ability), and π* (dipolarity/polarizability) parameters of native cellulose batches, carboxymethyl celluloses (CMCs), cellulose tosylates (CTs), and other derivatives with different degree of substitution (DS), chitine, amylose, amylopectine, and cellobiose are presented. Fe(phen)2(CN)2 [cis-dicyano-bis-(1,10)-phenanthroline-iron(II), (1)], Michler's ketone [bis-4,4′-(N,N-dimethylamino)benzophenone, (2)], 4-aminobenzophenone (3), coumarine 153 (4), and Reichardt's dye (5) were used as solvatochromic surface polarity indicators. The UV/Vis reflectance spectra of the five surface polarity indicators 1, 2, 3, 4, and 5, adsorbed on the samples from the organic solvents, were measured and the absorption maxima were used to calculate the α, β, π*, and ET(30) values of the polysaccharides surface. α, β, and π* depending on degree of crystallinity of the cellulose samples have been determined. α depends on both amount and strength of accessible acidic surface groups on the cellulose surface. It is significantly larger for crystalline sections than for amorphous parts. The π* scale is suitable for the classification of different cellulose batches, because it seems to be independent of inhomogeneities of the cellulose surface. The α-values of CMCs and CTs significantly decrease with increasing DS inasmuch the number of cellulosic-OH groups (Cell-OH) decreases. A slight increase of π* with DS is observed for CTs.

Solvatochromic Probe Behavior within Binary Room-Temperature Ionic Liquid 1-Butyl-3-Methyl Imidazolium Hexafluorophosphate plus Ethanol Solutions

Room-temperature ionic liquids (RTILs) have shown tremendous promise as replacements for the toxic and volatile organic solvents used in many applications. Depending on a particular application, addition of a “green” cosolvent can very easily modify/alter the physicochemical properties of the RTILs in a favorable fashion. Solvatochromic probe behavior within binary RTIL 1-butyl-3-methyl imidazolium hexafluorophosphate (BMIMPF6) + ethanol solutions are investigated using four popular probes, pyrene, 1-pyrenecarboxaldehyde, 1,3- bis-(1-pyrenyl)propane, and Reichardt's betaine dye. A simplified preferential solvation model based on the weighted mole-fraction probe response shows that the pyrene cybotactic region is rich in BMIMPF6 in comparison to the bulk composition. However, 1-pyrenecarboxaldehyde and 1,3- bis-(1-pyrenyl)propane solvation environments clearly indicate a cybotactic region dominated by ethanol. Reichardt's betaine dye shows absorbance maxima lower than that observed in either of the two neat components, BMIMPF6 or ethanol. This probe is well known to manifest the hydrogen-bond-donating (HBD) ability of the solvent system. HBD ability also depends on the dipolarity/polarizability of the solvent system. Ethanol has a higher HBD ability but lower dipolarity/polarizability than BMIMPF6. As the mole fraction of ethanol is increased, the increase in the HBD ability of the binary BMIMPF6 + ethanol solution is manifested through the unusual Reichardt's dye response.

Recognition of alkaline metals and amines by a chromogenic homooxacalix[3]arene receptor.

[structure: see text] The artificial host molecule 1, consisting of homooxacalix[3]arene and pyridinium N-phenolate dye (Reichardt dye E(T)1) has been prepared. Host 1 contains a proton-ionizable phenol group that acts as a chemical switch to generate color change against alkaline metals and various kind of amines.

Expanding the polarity range of ionic liquids

The polarity of several [X-mim]NTf 2 ionic liquids, as measured with solvatochromic dyes, Reichardt's dye and Nile Red, may be varied over a wide range by attachment of functional group-containing substituents (X) to the imidazolium cation.

A CIS study of solvent effects on the electronic absorption spectrum of Reichardt's dye

A configuration interaction singles wavefunction, in conjunction with a self-consistent reaction field and a simple Onsager spherical cavity model, has been used to calculate the solvent induced shifts in Reichardt's dye (RD). The results from this simple method are in good agreement with experiment for aprotic solvents, but large discrepancies exist for protic solvents. This discrepancy can be partially compensated for by including one explicit solvent molecule H-bonded to RD. Geometry optimization of the S1 state in RD predicts a pyramidal sp3 hybridized N atom and an overall structure that differs significantly from that in the S0 state. Analysis of the calculated dipole moments and selected molecular orbitals are in accord with previous analyses of the S0→S1 charge transfer transition in RD. However, the nature of the S0→S2 transition appears to change with solvent dielectric strength (ϵ). At low ϵ this transition seems to have significant charge transfer character that decreases as ϵ increases.

Structure and Surface Polarity of Poly(vinylformamide-co-vinylamine) (PVFA-co-PVAm)/Silica Hybrid Materials

Structure and surface polarity properties of poly(vinylformamide-co-vinylamine) (PVFA-co-PVAm)/silica hybrid materials are investigated by means of electrokinetic measurements, atomic force microscopy (AFM), and solvatochromic probes. AFM measurements show the complete covering of the silica surface with the PVFA-co-PVAm layer, which has a thickness between 0.5 and 2 nm depending on the content of the poly(vinylamine) (PVAm) component of the copolymer. The ET(30) surface polarity parameters of PVFA-co-PVAm/silica hybrid particles were investigated by two differently substituted Reichardt's dyes, 2,6-diphenyl-4-(2,4,6-triphenyl-N-pyridino)phenolate (1) and its lipophilic derivative 2,6-di(4-tert-butylphenyl)-4-[tris-2,4,6-(4-tert-butylphenyl-N-pyridino)]phenolate (2). Adsorption of the basic polymer PVFA-co-PVAm on silica significantly decreases the hydrogen bond donating capacity of the former silica surface, and therefore the ET(30) surface polarity decreases linearly with increasing the content of the P...

Probing the Surface Polarity of Poly(α-amino acids) and α-Amino Acid Crystals with Genuine Solvatochromic Dyes

Reichardt's ET(30) and Kamlet−Taft's α (hydrogen bond donor acidity), β (hydrogen bond acceptor basicity), and π* (dipolarity/polarizability) values for various poly(α-amino acids) [−NH−CH*(R)−CO−]n (PAs) and α-amino acid crystals [H3N+−CH*(R)−COO−]n (AACs) are presented. The ET(30) values of the solid poly(α-amino acids) are directly measured by UV/vis spectroscopy using Reichardt's dyes 1a and 1b as surface polarity indicators. Kamlet−Taft's α, β, and π* parameters for the various solid PAs and AACs are analyzed by means of Fe(phen)2(CN)2 [cis-dicyanobis(1,10-phenanthroline)iron(II)] (2), Michler's Ketone [4,4‘-bis(N,N-dimethylamino)benzophenone] (3), 4-aminobenzophenone (4), and an aminobenzofurandione dye (5) as solvatochromic surface polarity indicators. The surface polarity of AACs is determined by a quite strong hydrogen-bond-donating capacity (α = 0.6−0.96) and moderate dipolarity/polarizability (π* = 0.3−0.7). For the same substituent R, in general for PAs the α value is lower than the π* value, whereas for AACs the result is opposite. Increasing the size of the alkyl substituent R of PAs or AACs decreases the α and β values. It can be shown that the β value of solid PAs is a function of Taft's sterical parameter (Es)if the size of R decreases, the β value increasesindicating a strong influence of the steric effects of R on the accessibility of the peptide bond to hydrogen-bond-accepting probes. Theoretical ET(30) values for AACs are calculated by applying linear solvation energy relationships using the independently measured α and π* values of the solid acids according to ET(30) = [ET(30)]o + aα + sπ*, because ET(30) values cannot be directly determined for AACs.

On the Mechanism of Radical C−N Coupling in Type B Semiconductor Photocatalysis: A High-Pressure Study,

The CdS and CdS/SiO2 photocatalyzed addition of 2,5-dihydrofuran (2,5-DHF) to azobenzene in methanol solution affords 3-(2,3-dihydrofuryl)hydrazobenzene (1) as the major and hydrazobenzene (2) as the side product. According to 13C NMR and adsorption data, 2,5-DHF is adsorbed parallel to the surface through hydrogen bonding with [OH/SH] groups; adsorption constants of 18 and 30 L mol-1 are obtained for CdS and CdS/SiO2, respectively. This enhanced effect of the silica support favors formation of the addition product 1. Different from that, azobenzene exhibits adsorption constants identical within experimental error (11126 and 1059 L mol-1) for both photocatalysts and adsorbs most likely at Bronsted acid centers. These results are corroborated by corresponding adsorption studies with SiO2. The much better adsorption of 2,5-DHF onto CdS when performed in aqueous suspension is rationalized by comparison of adsorbent and adsorptive polarities, as determined by Reichardt's dye. The absence of any addition produ...

Photochemistry and Photophysics of (1-Naphthoyl)diphenylphosphine Oxide

(1-Naphthoyl)diphenylphosphine oxide (1) was synthesized and characterized and its photochemistry investigated using emission spectroscopy, pulse radiolysis, and nanosecond laser flash photolysis. Fluorescence quantum yields are low in aprotic polar and nonpolar solvents. In methanol, as a result of hydrogen-bonding, change of S1 from an n,π* state to a π,π* state leads to the decrease in the rate constant for intersystem crossing and results, finally, in an increase in fluorescence. Preferential solvation was evaluated using the ET indicator “Reichardt's dye” (RD). ETN values were determined by gradually increasing the concentrations of methanol in methanol/acetonitrile mixtures. Fluorescence quantum yields correlate with the ETN values. Photolysis of 1 yields diphenyl[1-naphthoyl)oxy]phosphine (6), formed mainly via cage recombination of radicals. No radicals were detected by either nanosecond laser flash photolysis or pulse radiolysis of 1 in aprotic solvents. However, photolysis in methanol yields rad...

ET(30) Surface Polarity Parameters of Alkyl- and Aryl-Group-Functionalized Silica Particles: Differentiating the Surface Environments by Means of the Application of Differently Substituted Reichardt's Dyes

ET(30) surface polarity parameters are presented for alkyl-functionalized silica particles. Sixteen different chemically modified Aerosil and LiChrospher samples were used as silicas with various degrees of grafting and different chain lengths. The surface polarities of the silica samples were examined by measuring the UV/vis absorption maxima of differently substituted 4-(2,4,6-triphenyl-N-pyridinio)phenolate betaine dyes adsorbed to functionalized silica samples suspended in 1,2-dichloroethane or cyclohexane.The value of the ET(30) surface polarity parameter of the silica particle decreases with increasing degree of functionalization of the silica surface with alkyl groups. The lengths of the alkyl groups have no observable influence upon the value of the ET(30) parameter. The measured value of the ET(30) surface polarity parameter of a partially alkyl-group-modified silica sample is lowered more by using dyes with sterically demanding alkyl substituents in the 2 and 6 position of the phenolate ring of the dye than by using the standard dye. Contributions of hydrogen bonds and dipolarity/polarizability effects on the specific ET(30) values measured of individual silica particles with various residual silanol and alkyl groups, respectively, are discussed.

The use of Reichardt's dye as an indicator of surface polarity

Download options Please wait... Article information DOI https://doi.org/10.1039/A901563I Article type Paper Download Citation New J. Chem., 1999,23, 725-731 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions The use of Reichardt's dye as an indicator of surface polarity D. J. Macquarrie, S. J. Tavener, G. W. Gray, P. A. Heath, J. S. Rafelt, S. I. Saulzet, J. J. E. Hardy, J. H. Clark, P. Sutra, D. Brunel, F. di Renzo and F. Fajula, New J. Chem., 1999, 23, 725 DOI: 10.1039/A901563I To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Duncan J. Macquarrie Stewart J. Tavener Gary W. Gray Paul A. Heath John S. Rafelt Sylvie I. Saulzet Jeff J. E. Hardy James H. Clark Pierre Sutra Daniel Brunel Francesco di Renzo Françoise Fajula