Spectroscopic characterization of p-phenylene vinylene (PV) oligomers. Part I: A homologous series of 2,5-diheptyloxy substituted PV-oligomers

Narwark, O.; Meskers, Stefan C. J.; Peetz, Ralf M.; Thorn‐Csányi, Emma; Bäßler, H.

doi:10.1016/s0301-0104(03)00334-3

Cited by 41 publications

(56 citation statements)

References 49 publications

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“…1); this is a commonly observed feature with related compounds [7,17,18] and in particular with the correspondent polymers [15,29], and is attributed to the wide range of vibrational and rotational degrees of freedom available in conjugated oligomers and polymers [16]. Substitution of an alkyl (HPV3P) by an alkyloxy (EHOPV3P, MPOPV3A) sidechain red-shifted the absorption maximum of the compound by %67 nm for the ethylhexyloxy and %80 nm for the methylpropyl-oxy substituents, see Table 1 [7,17,18]. For the PPV-trimers with ethylhexyloxy sidechain (EHOPV3P) substitution of the terminal end groups by the aromatic phenylene (EHOPV3PB) and anthracene (EHOPV3PA) groups red-shifted the absorption maximum…”

Section: Absorptionmentioning

confidence: 67%

“…b The underlined values are the wavelength maxima. with the compounds possessing alkyloxy derivatives may lie in the structural modification induced by the alkyloxy vs. alkyl sidechain, as has previously been observed [7,17,18] and discussed theoretically [31]. The electrondonor characteristics of the alkyloxy group will extend the p-electrons of the oxygen atoms to the oligomer backbone and as consequence the absorption and emission wavelength maxima are lower in energy.…”

Section: Fluorescencementioning

confidence: 80%

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Electronic spectral and photophysical properties of some p-phenylenevinylene oligomers in solution and thin films

Melo

Pina

Paolo³

et al. 2006

Chemical Physics

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A comprehensive photophysical and spectroscopic study of a new class of p-phenylenevinylene oligomers (PPV-trimers) possessing different alkyl and alkyloxy sidechain substituents and different end groups (aldehyde, C@C, phenylene and anthracene units) was undertaken in solution at room temperature (293 K), low temperature (77 K) and in thin films. The study comprises absorption, emission and triplet-triplet absorption spectra, together with quantitative measurements of quantum yields (fluorescence, intersystem crossing, internal conversion and singlet oxygen formation) and lifetimes. The data allow the determination of rate constants for all decay processes. From these, several conclusions could be drawn. Changing from alkyl to alkyloxy substituents does not change fluorescence and internal conversion yields but decreases the (already small) intersystem crossing yield. The introduction of anthracene at the terminal ends of the PPV-trimers leads to the lowest fluorescence yield reported in this study. Of particular importance is the fact that the fluorescence quantum yields in films are of the same order of magnitude as those in solution, which suggests the potential for use of these oligomers for light-emitting device applications. With one of the alkyloxy derivatives, a more detailed study of the early part of the fluorescence decay was made, and it was found that upon excitation a fast conformational relaxation process of the initially excited oligomer occurs, leading to a more planar conjugation segment.

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Section: Absorptionmentioning

confidence: 67%

Section: Fluorescencementioning

confidence: 80%

Electronic spectral and photophysical properties of some p-phenylenevinylene oligomers in solution and thin films

Melo

Pina

Paolo³

et al. 2006

Chemical Physics

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“…Such welldefined behavior is well-established and is the basis for our understanding of linear conjugated systems. 2,[19][20][21][22] It is clear, however, that both the short chain limit and the rate of decrease with increasing chain limit differ significantly with monomeric structure and the degree of coupling between the monomeric units. The differences in the long chain limit of the phenyl versus the acenes series mirrors the differences in band gaps of cis versus trans polyacetylene 7 and zigzag versus armchair singlewalled carbon nanotubes.…”

Section: Resultsmentioning

confidence: 99%

Structure−Property Relationships for Electron−Vibrational Coupling in Conjugated Organic Oligomeric Systems

O’Neill¹,

Byrne²

2005

J. Phys. Chem. B

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A series of π-conjugated oligomers containing one to six monomer units were studied by absorption and photoluminescence spectroscopy. As is common for these systems, a linear relationship between the positioning of the lowest-energy absorption and the highest-energy photoluminescence maxima plotted versus inverse conjugation length is observed, in good agreement with a simple nearly free electron model, one of the earliest descriptions of the properties of one-dimensional organic molecules. It was observed that the Stokes shift and therefore Huang-Rhys factor also exhibit a well-defined relationship with increasing conjugation length, implying a correlation between the electron-vibrational coupling and chain length. This correlation is further examined using Raman spectroscopy, whereby the integrated relative Raman scattering is seen to behave superlinearly with chain length. The Stokes shift and the Raman activity are also well-correlated in these systems. There is a clear indication that the vibrational activity and thus nonradiative decay processes are controllable through molecular structure.

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“…[24,25] Poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) was obtained from Covion. The structures of trimers and polymer are shown in Scheme 1.…”

Section: Methodsmentioning

confidence: 99%

Conformational Relaxation of p‐Phenylenevinylene Trimers in Solution Studied by Picosecond Time‐Resolved Fluorescence

Paolo¹,

et al. 2007

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Two p-phenylenevinylene (PV) trimers, containing 3'-methylbutyloxyl (in MBOPV3) and 2'-ethylhexyloxyl (in EHOPV3) side chains, are used as model compounds of PV-based conjugated polymers (PPV) with the purpose of clarifying the origin of fast (picosecond time) components observed in the fluorescence decays of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV). The fluorescence decays of MBOPV3 and EHOPV3 reveal the presence of similar fast components, which are assigned to excited-state conformational relaxation of the initial population of non-planar trimer conformers to lower-energy, more planar conformers. The rate constant of conformational relaxation k(CR) is dependent on solvent viscosity and temperature, according to the empirical relationship k(CR)=aeta(o) (-alpha)exp(-alphaE(eta)/RT), where aeta(o) (-alpha) is the frequency factor, eta(o) is the pre-exponential coefficient of viscosity, E(eta) is the activation energy of viscous flow. The empirical parameter alpha, relating the solvent microscopic friction involved in the conformational change to the macroscopic solvent friction (alpha=1), depends on the side chain. The fast component in the fluorescence decays of MEH-PPV polymers (PPVs), is assigned to resonance energy transfer from short to longer polymer segments. The present results call for revising this assignment/interpretation to account for the occurrence of conformational relaxation, concurrently with energy transfer, in PPVs.

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Spectroscopic characterization of p-phenylene vinylene (PV) oligomers. Part I: A homologous series of 2,5-diheptyloxy substituted PV-oligomers

Cited by 41 publications

References 49 publications

Electronic spectral and photophysical properties of some p-phenylenevinylene oligomers in solution and thin films

Electronic spectral and photophysical properties of some p-phenylenevinylene oligomers in solution and thin films

Structure−Property Relationships for Electron−Vibrational Coupling in Conjugated Organic Oligomeric Systems

Conformational Relaxation of p‐Phenylenevinylene Trimers in Solution Studied by Picosecond Time‐Resolved Fluorescence

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