The charge transfer mechanism and spectral properties of a near-infrared heptamethine cyanine dye in alcoholic and aprotic solvents

Zhou, Li Chuan; Zhao, G.; Liu, Ji Feng; Han, Kai; Wu, Yun Kou; Xiao, Pan; Sun, Mengtao

doi:10.1016/j.jphotochem.2006.10.027

Cited by 91 publications

(28 citation statements)

References 31 publications

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“…In addition, site-specific intermolecular hydrogen bonding interactions can also influence the electronic spectra, such as quenching fluorescence. [60][61][62][63][64][65][66][67] As discussed above, the S 2 fluorescence can be observed for QTCP and QBCP but not for QT and QTC. This may be correlated with the energy gap between S 2 and S 1 states.…”

Section: Density Of Statesmentioning

confidence: 99%

Photoinduced Intramolecular Charge Transfer and S₂ Fluorescence in Thiophene‐π‐Conjugated Donor–Acceptor Systems: Experimental and TDDFT Studies

Zhao

Chen

Sun

et al. 2008

Chemistry A European J

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207

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Experimental and theoretical methods were used to study newly synthesized thiophene-pi-conjugated donor-acceptor compounds, which were found to exhibit efficient intramolecular charge-transfer emission in polar solvents with relatively large Stokes shifts and strong solvatochromism. To gain insight into the solvatochromic behavior of these compounds, the dependence of the spectra on solvent polarity was studied on the basis of Lippert-Mataga models. We found that intramolecular charge transfer in these donor-acceptor systems is significantly dependent on the electron-withdrawing substituents at the thienyl 2-position. The dependence of the absorption and emission spectra of these compounds in methanol on the concentration of trifluoroacetic acid was used to confirm intramolecular charge-transfer emission. Moreover, the calculated absorption and emission energies, which are in accordance with the experimental values, suggested that fluorescence can be emitted from different geometric conformations. In addition, a novel S(2) fluorescence phenomenon for some of these compounds was also be observed. The fluorescence excitation spectra were used to confirm the S(2) fluorescence. We demonstrate that S(2) fluorescence can be explained by the calculated energy gap between the S(2) and S(1) states of these molecules. Furthermore, nonlinear optical behavior of the thiophene-pi-conjugated compound with diethylcyanomethylphosphonate substituents was predicted in theory.

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Section: Density Of Statesmentioning

confidence: 99%

Photoinduced Intramolecular Charge Transfer and S₂ Fluorescence in Thiophene‐π‐Conjugated Donor–Acceptor Systems: Experimental and TDDFT Studies

Zhao

Chen

Sun

et al. 2008

Chemistry A European J

Self Cite

207

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“…[19][20][21][22] This is surprising because it is well known that meso-substituted cyanines usually do not only exist as the all-trans isomer in the ground state but also in (various) cis form(s), with the proportions of the isomers depending on the nature of the substitution pattern in the polyA C H T U N G T R E N N U N G methine chain, the solvent and temperature. [29,[31][32][33] The impact of this behaviour on cyanine-based fluorescent probe and label design and performance has also been recognised and investigated.…”

Section: Quantum-chemical Calculationsmentioning

confidence: 99%

“…The most striking feature is the change in electron density at the meso-carbon atom: the p-electron density is virtually zero in the HOMO but high in the LUMO. To judge whether the difference between 2 (3) and 4 (5) is due to the involvement of an intramolecular charge transfer (ICT) process in the N-meso-substituted dyes as postulated by several researchers, [19,22] we also treated reference compounds 6 and 7 theoretically, which possess a hydrogen atom instead of the amino substituent at the meso position (Scheme 2). Figure 2 and Table S2 (see the Supporting Information) show that qualitatively all the features are similar to those of 2 and 3.…”

Section: Quantum-chemical Calculationsmentioning

confidence: 99%

“…[19][20][21] Additionally, symmetric cyanine dyes that carry a (substituted) amino donor group in the meso position show pronounced Stokes shifts, [19] potentially rendering them more advantageous for many applications as labels and probes. However, the aforementioned [19][20][21] and several other recent reports [22] on such dyes as fluorescent probes suggest that the underlying photophysical and photochemical mechanisms that determine the spectroscopic response are still a matter of controversy. Moreover, understanding these features is not only important for future dye design, but can even lead to the development of entirely new signalling protocols.…”

Section: Introductionmentioning

confidence: 99%

“…[23] The aim of the present work was to elucidate the signalling pathways in N-meso-substituted cyanine dyes in the presence of species only able to form coordinative bonds (metal ions) and species such as protons that form covalent bonds with the reporter dye. Moreover, to avoid complications presumably based on the rich photochemistry of this class of dyes, [19][20][21][22] we attempted to develop an alternative NIR-colourimetric signalling protocol that relies on the Cu II -promoted aggregation and citrate-induced deaggregation of a meso-cyclam-substituted heptamethine cyanine dye in water. Citrate is a key player in human and plant nutrition and metabolism rendering its analysis topical.…”

Section: Introductionmentioning

confidence: 99%

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On the Signalling Pathways and Cu^II‐Mediated Anion Indication of N‐meso‐Substituted Heptamethine Cyanine Dyes

Descalzo

Rurack

2009

Chemistry A European J

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Join or attack: meso-Cyclam-substituted heptamethine cyanine dye 1 responds very differently to the presence of metal ions and protons. Whereas the former are embraced in a host-guest complex, the latter attack the cyanine pi system (see picture). In the presence of Cu(II), 1 selectively forms near-infrared absorbing aggregates in buffered solution that allow the determination of citrate by using colourimetry.Three mid-chain rigidified heptamethine cyanine dyes substituted with dimethylamino or cyclam groups at the meso position of the polymethine chain have been prepared and studied both experimentally and theoretically with respect to their spectroscopic response toward protons and various metal ions. Despite a potentially rich conformational ground-state chemistry, the spectroscopic studies revealed that the behaviour of the dyes is in agreement with Kuhn's classic polymethine dye theory. Coordination of metal ions and protonation of the alkyl amino groups in the cyclam moiety accordingly lead to moderate bathochromic shifts in absorption and reduced Stokes shifts. In contrast, protonation of the dimethylamino-substituted derivatives occurs at the polymethine chain, transforming the heptamethine into a trimethine-type chromophore with concomitant gigantic spectral blueshifts. In the presence of Cu(II) in buffered aqueous solution, the cyclam-substituted dye selectively forms near-infrared absorbing aggregates. The latter allow the determination of citrate under realistic conditions by changes in absorption at wavelengths greater than 800 nm, which results from a disruption of the aggregates when citrate binds to Cu(II). The copper ions thus act as mediators in a signalling reaction that constitutes a colourimetric displacement assay.

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Solute–Solvent Hydrogen Bond Formation in the Excited State. Experimental and Theoretical Evidence

Matei

Ionescu

Hillebrand

2010

Hydrogen Bonding and Transfer in the Excited State

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Hydrogen bonds (H-bonds) are of great importance in biological systems, as they are responsible for the secondary structure of proteins and nucleic acids and are also involved in the mechanisms of enzyme catalysis. Supramolecular chemistry makes use of H-bonds in building up novel compounds of various architectures.The identification of these interactions and the analysis of their influence on the photophysical properties are also important in designing new fluorophores for different applications, the processes involved being rather complex in nature and often only partially understood.The main feature reflecting H-bond interaction in both the ground and excited states is the solvatochromic effect on the absorption and fluorescence spectra. This implies that changes in the solvent nature or composition produce shifts in the position, shape and intensity of the spectral bands. The source of solvatochromic shifts is the different solvation of the ground and excited states: depending on the relative stabilization of these states by solvents, bathochromic (positive)or hypsochromic (negative)shifts of the maximum of the band can be observed experimentally. Thus, such changes are indicative of the interactions occurring between the solute and the solvent in its immediate vicinity. The solute-solvent interactions are classified into:1. non-specific interactions caused by polarity/polarizability effects; 2. specific interactions, such as H-bonds.

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The charge transfer mechanism and spectral properties of a near-infrared heptamethine cyanine dye in alcoholic and aprotic solvents

Cited by 91 publications

References 31 publications

Photoinduced Intramolecular Charge Transfer and S₂ Fluorescence in Thiophene‐π‐Conjugated Donor–Acceptor Systems: Experimental and TDDFT Studies

Photoinduced Intramolecular Charge Transfer and S₂ Fluorescence in Thiophene‐π‐Conjugated Donor–Acceptor Systems: Experimental and TDDFT Studies

On the Signalling Pathways and Cu^II‐Mediated Anion Indication of N‐meso‐Substituted Heptamethine Cyanine Dyes

Solute–Solvent Hydrogen Bond Formation in the Excited State. Experimental and Theoretical Evidence

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The charge transfer mechanism and spectral properties of a near-infrared heptamethine cyanine dye in alcoholic and aprotic solvents

Cited by 91 publications

References 31 publications

Photoinduced Intramolecular Charge Transfer and S2 Fluorescence in Thiophene‐π‐Conjugated Donor–Acceptor Systems: Experimental and TDDFT Studies

Photoinduced Intramolecular Charge Transfer and S2 Fluorescence in Thiophene‐π‐Conjugated Donor–Acceptor Systems: Experimental and TDDFT Studies

On the Signalling Pathways and CuII‐Mediated Anion Indication of N‐meso‐Substituted Heptamethine Cyanine Dyes

Solute–Solvent Hydrogen Bond Formation in the Excited State. Experimental and Theoretical Evidence

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Product

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Photoinduced Intramolecular Charge Transfer and S₂ Fluorescence in Thiophene‐π‐Conjugated Donor–Acceptor Systems: Experimental and TDDFT Studies

Photoinduced Intramolecular Charge Transfer and S₂ Fluorescence in Thiophene‐π‐Conjugated Donor–Acceptor Systems: Experimental and TDDFT Studies

On the Signalling Pathways and Cu^II‐Mediated Anion Indication of N‐meso‐Substituted Heptamethine Cyanine Dyes