pH Dependence of electronic and nuclear magnetic resonance spectra of isomeric cyanine dyes

Feldman, Lawrence H.; Herz, Alexander; Regan, Thomas H.

doi:10.1021/j100852a024

Cited by 26 publications

(4 citation statements)

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“…For the aromatic hydrogens even at the lowest concentration in Table , these chemical shifts are ca. 0.5 ppm smaller than the values reported for pinacyanol chloride in dimethyl sulfoxide (DMSO) . As is well-known for chromonic systems, aggregation leads to smaller chemical shifts for the aromatic hydrogens because of shielding due to the presence of neighboring aromatic rings (“ring current effect”). , Typically there is a difference between the chemical shifts of monomers and aggregates of ca.1−1.8 ppm , Only a single averaged spectrum is observed (rather than separate monomer and aggregate peaks) because of fast molecular exchange between the two states (>10 3 s −1 ).…”

Section: Resultsmentioning

confidence: 99%

“…Note that the largest changes are for the hydrogens in the 12 conjugated bonds at the bottom of molecule (Figure ). Also, the shift change of the CH 2 groups , is reasonably large. Thus, we hypothesize that within the aggregates the conjugated bottom moiety, including the three-carbon link, is in close proximity to the aromatic groups of stack neighbors.…”

Section: Resultsmentioning

confidence: 99%

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Chromonic Liquid Crystalline Phases of Pinacyanol Acetate: Characterization and Use as Templates for the Preparation of Mesoporous Silica Nanofibers

2011

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We report on the self-aggregation of the cationic dye pinacyanol acetate and its use for the preparation of nanostructured silica via templated sol-gel reaction. The dye forms nematic and hexagonal chromonic liquid crystals at low concentrations in water (i.e., from 0.75 wt %); the type of counterion appears to play an important role in liquid crystal formation. From analysis of small X-ray scattering (SAXS) curves, it is inferred that dye aggregates have the morphology of hollow long tubes with one-molecule-thick walls; the diameter of the tubes does not to change much with concentration. The dye aggregates can be aligned by shear or by a magnetic field. The high-resolution (1)H NMR spectra show that aggregation takes place over a range of concentrations rather than having a sharp "critical" aggregation. Within the aggregates the conjugated moiety, including the three-carbon link, is in close proximity to the aromatic groups of stack neighbors. On the other hand, dye aggregates direct the formation of silica nanofibers synthesized via sol-gel reaction, mimicking the elongated structures found in aqueous media. The nanofibers show a hierarchical organization; i.e., they contain hexagonal arrays of 3 nm cylindrical mesopores left after calcination of the templating molecules, and the pore walls are 2.7 nm thick. As the nanofibers form entangled networks, the obtained materials also show interparticle porosity. The present findings open new possibilities for the use of commercial cationic dyes in the synthesis of nanostructured materials.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Chromonic Liquid Crystalline Phases of Pinacyanol Acetate: Characterization and Use as Templates for the Preparation of Mesoporous Silica Nanofibers

2011

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“…If the pD fell below 6.4, protonation (deuterionation) of the dye could be detected by the appearance of new resonances in the spectra. 6 Determinations of the pD of dye solutions established that it remained at 7.0 ± 0.1.…”

Section: Methodsmentioning

confidence: 99%

Aggregation of 1,1'-diethyl-2,2'-cyanine chloride as studied by nuclear magnetic resonance

Graves¹,

Rose²

1975

J. Phys. Chem.

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The dye, l,l'-diethyl-2,2'-cyanine chloride, was studied in aqueous solution using Fourier transform proton magnetic resonance. The concentration dependencies of the chemical shifts for several different dye protons were determined over a concentration range of 2 X 10-2 to 3 X 10-5 M. All resonances shifted to higher applied field as dye concentration increased, establishing an aggregate structure in which dye molecules stack face to face with considerable overlap of the quinolinium ring system. In dilute solutions where only a monomer <=> dimer equilibrium occurs, the nmr data are interpreted in terms of "ring-current" theory and a dimer model that leads to Kb ~1X 103 M ~l. At higher concentrations, greater degrees of aggregation occur, which, by 2 X 10~2 M, shift dye aromatic protons -0.36 ppm compared with the monomer values. This shift change is interpreted in terms of a polymer composed of units similar to the dimer. Little specific evidence for any unique J-aggregate structure could be obtained. In D2O solutions, the methinyl proton was replaced slowly by deuterium and the rate was studied from pD 7 to 10.6. A rate constant for the acidcatalyzed process of 5 X 102 M~1 sec-1 was found for dye solutions at zero ionic strength.

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“…While electronic factors derived from the presence and positioning of halogens attached to the dye core likely contribute to the observed deviation in compound basicity, only the ohalogenated species displayed bathochromically shifted absorption signals characteristic of J-aggregation in the aqueous buffer solutions at the low concentration studied (3 μM), as shown in Figure 3b. Previous studies 38,39 have shown that pK a 's differ substantially between monomers and aggregates; thus, the propensity of the o-halogenated derivatives to form J-type aggregates under the studied conditions could also be a contributing factor to their observed lower basicity. The striking difference in pH effects between regioisomers, C8S3-o-Br and C8S3-p-Br, is clear by comparing Figure 3b and c. In the case of C8S3-p-Br (Figure 3c), there is a concomitant stepwise bleaching with increased acidity, whereas the o-Br isomer (Figure 3b) first undergoes aggregation (more below) with buffer introduction, followed by visible bleaching at pH 3.…”

Section: ■ Results and Discussionmentioning

confidence: 82%

Synthetic Access to Benzimidacarbocyanine Dyes to Tailor Their Aggregation Properties

et al. 2021

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Developing structure−aggregation relationships of cyanine dyes is crucial for controlling their optical properties for various uses. This study develops a synthetic route and the structure-dependent self-assembly of a family of benzimidacarbocyanine dyes for J-or H-aggregation properties. It was found that both the presence and placement of halogen atoms play a defining role in the resulting supramolecular interactions of these compounds.

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pH Dependence of electronic and nuclear magnetic resonance spectra of isomeric cyanine dyes

Cited by 26 publications

References 1 publication

Chromonic Liquid Crystalline Phases of Pinacyanol Acetate: Characterization and Use as Templates for the Preparation of Mesoporous Silica Nanofibers

Chromonic Liquid Crystalline Phases of Pinacyanol Acetate: Characterization and Use as Templates for the Preparation of Mesoporous Silica Nanofibers

Aggregation of 1,1'-diethyl-2,2'-cyanine chloride as studied by nuclear magnetic resonance

Synthetic Access to Benzimidacarbocyanine Dyes to Tailor Their Aggregation Properties

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