Surface-enhanced resonance Raman scattering study on the structure of a merocyanine dye, 4-(2-(4-hydroxyphenyl)ethenyl)-1-methylpyridinium, adsorbed on silver surfaces in water and in acetonitrile

Mineo, Yasushi; Itoh, Koichi

doi:10.1021/j100159a063

Cited by 9 publications

(7 citation statements)

References 5 publications

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“…The experimental results are supported with DFT calculations. Earlier reports on the infrared reflection-absorption ( Itoh et al, 1992 ), resonance Raman intensity analysis ( Leng et al, 2004 ) and SERRS ( Tsukada et al, 1989 ; Mineo and Itoh, 1991 ; Pajchrowski et al, 2007 ) studies of MC have indicated the presence of trans -conformation on the metal surface, which is in agreement with this study. Thus, multi-faceted application of MCH + /MC in bio sciences, materials and chemistry has motivated the present study, with an aim to gain thorough understanding of its molecular level behavior on the nanostructured surface of SCFs.…”

Section: Introductionsupporting

confidence: 92%

Conformational Selectivity of Merocyanine on Nanostructured Silver Films: Surface Enhanced Resonance Raman Scattering (SERRS) and Density Functional Theoretical (DFT) Study

et al. 2022

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In this study, detailed structural and vibrational analysis of merocyanine has been investigated using Raman, surface enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS). The Raman, SERS and SERRS studies aided by density functional theoretical (DFT) calculations clearly established the prevalence of the trans- and cis-conformers of the protonated form of merocyanine (MCH+) in solid and acetonitrile solution. The binding characteristics of merocyanine adsorbed on nanostructured silver-coated films (SCFs) were investigated using excitation-dependent SERS, concentration-dependent SERRS and DFT studies. The conformers of merocyanine involved in the surface adsorption processes were recognized. The prominent marker bands observed at 1538 (ethylenic C=C stretch) and 1133 cm−1 (pyridinium C-N stretch) in the Raman spectrum of merocyanine in acetonitrile shifted to 1540 and 1126 cm−1, respectively on the nanostructured SCFs. The shift in the marker bands is associated with either the preferential binding of selective conformer or change in resonance equilibrium between the benzenoid and quinoid forms. The excitation wavelength dependent SERS spectrum infers that in addition to the major contribution from the electromagnetic enhancement, chemical (resonance) effect leads to the amplification of the 1540 cm−1 band. The concentration-dependent SERRS study showed maximum enhancement for the nanostructured SCFs functionalized with 1 μM concentration of merocyanine, indicative of monolayer coverage. For lower concentrations of merocyanine, the SERRS signal intensity reduced without any alteration in the peak positions. The SERRS study thus, revealed sub-nanomolar (0.1 nM) sensing of merocyanine using nanostructured SCFs with the analytical enhancement factor (AEF) of ∼ 1010 for the 1126 cm−1 and 1540 cm−1 Raman bands for MC concentration of 0.1 nM. In this study, combination of SERRS and DFT have clearly established the predominance of trans-MCH+ on the nanostructured silver surface with minor contribution from cis-MCH+, which remain exclusively bound to the surface via the phenoxyl ring O atom. This conformational surface selectivity of geometrical isomers of merocyanine using nanostructured surfaces can be further explored for energy efficient and economical separation of geometrical isomers.

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Section: Introductionsupporting

confidence: 92%

Conformational Selectivity of Merocyanine on Nanostructured Silver Films: Surface Enhanced Resonance Raman Scattering (SERRS) and Density Functional Theoretical (DFT) Study

et al. 2022

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“…In making these assignments we have preserved the calculated frequency ordering and required that strong Raman lines be assigned to in-plane, relatively symmetric motions. We have also made use of vibrational spectra and normal mode analyses of related molecules, particularly those containing the N -alkylpyridinium moiety. − The 1496 cm -1 line is assigned to a normal mode calculated at 1547 cm -1 which involves stretching of the C e -donor ring bond and of the N−C and N−alkyl bonds in the donor ring. The 1036 cm -1 line is assigned as the “trigonal” deformation of the donor pyridinium ring.…”

Section: Discussionmentioning

confidence: 99%

Resonance Raman Intensity Analysis of Merocyanine Dimers in Solution

2004

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Resonance Raman excitation profiles and absolute cross sections are presented for three closely related merocyanine dyes as monomers in dichloromethane solution and as H-dimers in dioxane solution. For both monomers and dimers the absorption spectra and the resonance Raman intensities of the 24 to 30 strongest vibrations are quantitatively simulated using time-dependent wave packet propagation methods to determine the geometry changes along each Franck-Condon active mode upon electronic excitation, as well as the homogeneous and inhomogeneous electronic line widths. In addition, an approach previously formulated to describe the vibronic structure of an excitonically coupled homodimer with multiple vibrational modes [Kelley, A. M. J. Chem. Phys. 2003, 119, 3320-3331] is applied to model the dimer spectra. Comparison of these two calculations demonstrates that when the intermonomer coupling is strong the theoretical absorption and resonance Raman spectra of the dimer can be very well approximated by treating the system as a "supermolecule" having a single electronic transition with appropriately rescaled vibrational displacements, transition dipole, and electronic zero-zero frequency. The experimental dimer spectra exhibit the reduced Franck-Condon activity expected from distributing the electronic excitation over two monomers. However, deviations in the intensity patterns for individual vibrations suggest additional, more specific effects of dimerization, and the electronic transition moment for the lowest allowed transition of the monomer is not conserved upon dimer formation. An excitonically coupled monomer model therefore appears inadequate to describe the electronic excitations in these strongly coupled noncovalent dimers.

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“…This class of compounds has been used as sensitizers in color photography, 19 and due to their extreme hyperpolarizability they are used in nonlinear optics [20][21][22][23][24][25] and in electrochromics. [26][27][28][29][30] Furthermore, they seem to be promising for solar-energy conversion and in imaging technology.…”

Section: Introductionmentioning

confidence: 99%

Femtosecond Dynamics of a Simple Merocyanine Dye: Does Deprotonation Compete with Isomerization?

et al. 2000

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The primary photochemistry of the trans isomer of a simple merocyanine dye of the stilbazolium betaine type 1-methyl-4-(4′-hydroxytyryl)pyridinium betaine (M trans ) and its conjugate acid MH + trans in aqueous solution is studied by femtosecond time-resolved pump probe spectroscopy. The measured rate of the primary photodynamics is determined to be k ) 1.1 × 10 12 s -1 for M trans at pH 10 and 0.8 × 10 12 s -1 for MH + trans at pH 6. This was assigned to either conformational changes or a simple vibrational relaxation before the actual isomerization takes place. Wavelength excitation studies give support for the former assignment. These results are discussed in terms of the recent results found for the primary processes of retinal in bacteriorhodopsin. Time-resolved transient measurements show that no excited-state deprotonation of MH + trans occurs in aqueous solutions at pH 6 or pH 0, suggesting that the deprotonation occurs on a longer time scale than the picosecond time domain. This is in agreement with present theories of intermolecular proton-transfer reactions, which require solvent reorganization as well as the time of deprotonation estimated from the pK a value of this molecule in the excited state. The results of our MO calculations on the electronic structure of these two compounds could account for the fact that, while MH + trans photoisomerizes, its deprotonated form does not.

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Surface-enhanced resonance Raman scattering study on the structure of a merocyanine dye, 4-(2-(4-hydroxyphenyl)ethenyl)-1-methylpyridinium, adsorbed on silver surfaces in water and in acetonitrile

Cited by 9 publications

References 5 publications

Conformational Selectivity of Merocyanine on Nanostructured Silver Films: Surface Enhanced Resonance Raman Scattering (SERRS) and Density Functional Theoretical (DFT) Study

Conformational Selectivity of Merocyanine on Nanostructured Silver Films: Surface Enhanced Resonance Raman Scattering (SERRS) and Density Functional Theoretical (DFT) Study

Resonance Raman Intensity Analysis of Merocyanine Dimers in Solution

Femtosecond Dynamics of a Simple Merocyanine Dye: Does Deprotonation Compete with Isomerization?

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