The effect of solvents on the electronic structure of symmetetrical polymethinecyanines 1H- and 13C-NMR Spectroscopic investigations

Wähnert, M.; Dähne, S.; Radeglia, R.; Alperovich, Michael; Levkoev, I. I.

doi:10.1016/0378-4487(77)80039-3

Cited by 17 publications

(10 citation statements)

References 42 publications

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“…As seen, the values of the charges alternate strongly, and the alternation of the charges in the cations and anions is opposite in phase. This agrees with the alternation of the 13 C chemical shifts of neighboring atoms in both cationic and anionic polymethine dyes: 90-120 ppm for the positions with excess electron density and 150-170 ppm for the positions with an electron density deficiency [29,[107][108][109]. At the same time the difference in the value of the chemical shifts in neutral polyenes amounts to 1-2 ppm, while the values themselves are close to 130 ppm [110][111][112].…”

Section: Quantum-chemical Modellingsupporting

confidence: 82%

The Solitonic Nature of the Electronic Structure of the Ions of Linear Conjugated Systems

Kachkovskii

2005

Theor Exp Chem

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Features of the electron density distribution in the ground and excited states, the position of the energy levels, and the equilibrium molecular geometry of the ions of linear p-electron systems, including conjugated polymers and oligomers, cationic and anionic polymethine dyes, and the radical-ions of a,w-substituted polyenes, are reviewed. By using the soliton concept it was possible to explain many unusual properties of this type of organic compound: The quasimetallic conductivity, the marked change in the spectral characteristics of ionic dyes absorbing and emitting light in the near IR region of the spectrum, etc. It was shown on the basis of semiempirical and nonempirical calculations that the charges in collective p-electronic systems form soliton waves, the width of which does not depend on the length of the molecule. In the excited state the size of the solitons increases significantly. The introduction of donor and acceptor terminal groups can destroy the symmetry of the charge distribution and molecular geometry at a conjugation chain of critical length exceeding the dimensions of the soliton. It was established that the injection of electrons/holes not only leads to the appearance of a soliton level at the center of the energy gap but is also accompanied by significant displacement of the top of the valence band and the bottom of the conduction band.

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Section: Quantum-chemical Modellingsupporting

confidence: 82%

The Solitonic Nature of the Electronic Structure of the Ions of Linear Conjugated Systems

Kachkovskii

2005

Theor Exp Chem

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“…To examine the relationship of the present dioxaborine polymethines to more typical cyanines, we compared the 13 C NMR shifts for the polymethine carbon nuclei of 1a − d to those of their indole-terminated analogues Ia − d (Figure ). , In the case of 1a , an HSQC spectrum was used to unambiguously assign the polymethine nuclei (see the Supporting Information). The chemical shift data are shown in Table , and the variations in shift with substituent are illustrated graphically in the Supporting Information. Both classes of dye show very similar patterns in the chemical shifts; in particular, the α and γ methine carbons are generally shifted upfield relative to the β carbons, consistent with high positive charge densities on the α and γ positions.…”

Section: Resultsmentioning

confidence: 99%

Dioxaborine- and Indole-Terminated Polymethines: Effects of Bridge Substitution on Absorption Spectra and Third-Order Polarizabilities

et al. 2011

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Cyanine-like dyes are promising candidates for third-order nonlinear optical (NLO) applications such as all-optical switching. Here, we examine the consequences for linear and nonlinear optical properties of varying substituents on the central methine unit of bis(dioxaborine)-terminated anionic pentamethines and bis(indole)-terminated cationic heptamethines. The variation in absorption maxima and electrochemical potentials with structure can generally be rationalized using the Dewar-Knott rules, providing that mesomeric and inductive electron-withdrawal and donation are explicitly considered. In the case of nitro- and (dioxaborinyl)vinyl-substituted bis(dioxaborine) pentamethines, the low-energy transitions are significantly broadened, consistent with (1)H NMR spectra indicating deviation from cyanine-like geometry. Real and imaginary parts of the third-order polarizabilities, Re(γ) and Im(γ), were measured at 1.3 μm. The values of Im(γ) indicate that the values of Re(γ) are significantly resonantly enhanced, while the positive value of Re(γ) found for a nitro-substituted dioxaborine example is atypical for a symmetrical polymethine and suggests that a two-state treatment is inadequate. The relevance of these results to chromophore design for third-order NLO applications is discussed.

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“…Thus, in aromatic solvents, the positions of the absorption bands undergo bathochromic shifts when in media of higher polarisability [7], because polarisable solvent molecules apparently stabilise cations in the Frank-Condon excited state. At the same time, the influence of the nucleophilicity of aromatic solvents is abnormally weak owing to the formation of -complexes between the aromatic molecules and organic cations [19,20]. In alcohols or mixtures containing water, some CBP derivatives form hydrogen bonds with the solvent molecules and demonstrate a dependence on the electrophilic properties of the medium.…”

Section: Discussionmentioning

confidence: 99%

Spectral Properties of Dyes with Interfragmental Charge Transfer: Solvatochromism and Solvatofluorochromism of 2-(3-Coumaroyl)-benzopyrylium Perchlorates

Sanin

Novikov

Roshal

2014

International Journal of Spectroscopy

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The paper deals with the spectral properties of dyes with interfragmental charge transfer, in particular, derivatives of 2-(3-coumaroyl)benzopyrylium (CBP) perchlorates. The positions of long-wavelength absorption and emission bands, quantum yields, and lifetimes of fluorescence were measured, mostly in aprotic solvents. Regression analysis of the relationship between the spectral characteristics of CBP and the main solvent parameters (polarity, polarisability, nucleophilicity, and electrophilicity) was carried out. It was found that the characteristics of CBP depend mainly on two solvent parameters—polarity and/or nucleophilicity. An increase in these parameters results in a hypsochromic shift of absorption bands and a decrease of lifetimes and fluorescence intensity. The positions of the emission bands can demonstrate either hypsochromism or bathochromism, depending on the nature of the substituents. The solvatofluorochromic effects are not as strong as the solvatochromic ones. We believe that the spectral behaviour of CBP can be explained by cation depolarisation and by a decrease in the stability of nucleophilic complexes with solvent molecules that is associated with interfragmental charge transfer following excitation, relaxation, and radiative deactivation of the excited state.

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The effect of solvents on the electronic structure of symmetetrical polymethinecyanines 1H- and 13C-NMR Spectroscopic investigations

Cited by 17 publications

References 42 publications

The Solitonic Nature of the Electronic Structure of the Ions of Linear Conjugated Systems

The Solitonic Nature of the Electronic Structure of the Ions of Linear Conjugated Systems

Dioxaborine- and Indole-Terminated Polymethines: Effects of Bridge Substitution on Absorption Spectra and Third-Order Polarizabilities

Spectral Properties of Dyes with Interfragmental Charge Transfer: Solvatochromism and Solvatofluorochromism of 2-(3-Coumaroyl)-benzopyrylium Perchlorates

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