Photophysical and theoretical studies of naphthalene-substituted oligothiophenes

Melo, J. Sérgio Seixas de; Silva, L.; Kuroda, Masami

doi:10.1063/1.1397310

Cited by 54 publications

(110 citation statements)

References 23 publications

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“…In the case of EHOPV3P and HPV3P, where virtually no change in the / F value is observed upon going to 77 K this was attributed to the fact that the S 1 state probably has the same geometry as that found at RT [7]. The decrease of the / F values upon lowering the temperature contrasts with the behaviour found for thiophene oligomers where an increase or constancy of this value was observed [20,23]. Thus the marked change (either increase or decrease) in the / F values upon going to LT can be associated with induced conformational changes, which is also in agreement with the marked redshift of the absorption and emission spectra when compared to the RT data.…”

Section: Solution and Solid-state Photophysical Behaviourmentioning

confidence: 84%

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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: Solution and Solid-state Photophysical Behaviourmentioning

confidence: 84%

“…The / T values were obtained by comparing the DOD at 525 nm of a benzene solution of benzophenone (the standard) and of the compound (optically matched at the laser wavelength) using the equation [23,24]:…”

Section: Spectroscopic Measurementsmentioning

confidence: 99%

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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“…The optical properties of polymers P1-P4 were examined, [74][75][76][77] and the data are summarized in Table 2. Figure 4a shows their UV-vis absorption spectra in CHCl 3 (1.0Â10 À5 M).…”

Section: Oligothiophene-stacked Polymers Y Morisaki Et Almentioning

confidence: 99%

“…64 It is suggested that this absorption band is assigned to the S 0 -S 1 transition of the bithiophene-naphthalene moiety and the S 1 state adopts a quinoidal-like structure of thiophene with naphthalene. 75,76 The bithiophenes in P1 as well as oligothiophenes in P2-P4 have difficulty in rotating freely because of the hexyl Figure 3 Matrix-assisted laser desorption ionization time-of-flight mass spectrum of polymer P1 using all-trans-retinoic acid as a matrix.…”

Section: Oligothiophene-stacked Polymers Y Morisaki Et Almentioning

confidence: 99%

Naphthalene-based oligothiophene-stacked polymers

Morisaki

Fernandes

Chujo

2010

Polym J

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We report the synthesis and properties of p-stacked polymers consisting of oligothiophene and naphthalene as the stacked p-system and the scaffold, respectively. The titled polymers were obtained by the Suzuki-Miyaura coupling reaction. Oligothiophene units were layered in proximity, B3.0 Å from each other. Contribution of the quinoidal structure of the oligothiophene units involving the naphthalene scaffolds in the excited state resulted in relatively high photoluminescence quantum efficiencies. The polymers have potential application to optoelectronic devices such as hole-transporting materials. Polymer Journal (2010) 42, 928-934; doi:10.1038/pj.2010.101; published online 27 October 2010Keywords: conjugated polymers; p-stacked polymers; oligothiophene; redox polymers; synthesis INTRODUCTIONCommon conjugated polymers generally consist of sp-and/or sp 2 -carbon frameworks, and p-electrons are delocalized throughout the polymer backbone. Such conjugated polymers have attracted considerable attention because of their good processability and their readily tunable electronic and optical properties. [1][2][3] Recently, a new type of conjugated polymer that exhibits through-space interactions of pelectron systems has been developed. Poly(dibenzofulvene)s, 4-11 7,7-diarylnorbornane-containing conjugated polymers, 12,13 cyclophanecontaining polymers and face-to-face ferrocene polymers [36][37][38] have been synthesized, and their optical and electrochemical properties have been studied in detail. Polymers with layered aromatic rings and p-electron systems have also been investigated; 39-53 for example, Chen et al. 53 recently reported the synthesis and formation of a twodimensional assembly of polymeric ladder phanes containing face-toface p-electron systems. These polymers have potential applications in optoelectronic devices and single-molecular devices such as singlemolecular wires.Cofacially aligned p-electron systems have an important role in biochemistry and material chemistry; DNA has face-to-face base pairs stacked in the double-stranded main chains, 54 and the performance of organic optoelectronic devices strongly depends on the arrangement of the p-electron systems. 55 We have recently reported the synthesis of aromatic-ring-layered polymers using xanthene compounds as scaffolds. [40][41][42][43][44][45][46][47] [2.2] Paracyclophane-layered polymers, which mimic multilayered cyclophanes, 56-59 exhibited fluorescence resonance energy transfer from the layered paracyclophanes to the end-capping groups. The use of xanthene as a scaffold enabled us to introduce various aromatic compounds, such as phenylenes, 44 carbazoles, 45 thiophenes 46 and anthracene, 47 into the polymers, with the distance between the layered aromatic units being B4.5 Å . Our next target is to construct layered and p-stacked aromatic systems in proximity, less than the sum of the van der Waals radius (3.40 Å ) of an sp 2 -carbon, in the polymer backbone.

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“…33 Triplet-singlet difference absorption spectra and yields were obtained using an Applied Photophysics laser flash photolysis equipment pumped by a Nd:YAG laser (Spectra Physics) with excitation wavelengths of 355 nm (leuco forms) and 535 nm (keto forms) as described elsewhere. 34 First-order kinetics was observed for the decay of the lowest triplet state. The transient spectra (300-700 nm) were obtained by monitoring the optical density change at 5-10 nm intervals, averaging at least 10 decays at each wavelength.…”

Section: Methodsmentioning

confidence: 99%

Photophysical and Spectroscopic Studies of Indigo Derivatives in Their Keto and Leuco Forms

Melo¹,

Moura²,

Melo³

2004

J. Phys. Chem. A

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A comprehensive spectroscopic and photophysical study of the keto and leuco forms of indigo and three other ring-substituted derivatives in solution was performed. The characterization involves absorption, fluorescence, and triplet-triplet absorption spectra, making it possible to obtain the quantum yields for fluorescence (φ F ), singlet-triplet intersystem crossing (φ ISC ), internal conversion (φ IC ), and lifetimes for fluorescence (τ F ) and triplet decay (τ T ). For the case of the keto forms, pulse radiolysis experiments have revealed the existence of a triplet acceptor (from energy transfer from different donors) for the indigo, purple, and indirubin compounds. It is shown that with the keto form the major deactivation pathway involves internal conversion from the lowest singlet excited state to the ground state whereas with the leuco form there is competition between internal conversion, triplet formation, and fluorescence deactivation processes. Furthermore, leuco forms present much higher Stokes shifts compared with keto ones, suggesting an excitedstate geometry different from the ground-state geometry, possibly involving rotational photoisomerization.

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Photophysical and theoretical studies of naphthalene-substituted oligothiophenes

Cited by 54 publications

References 23 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

Naphthalene-based oligothiophene-stacked polymers

Photophysical and Spectroscopic Studies of Indigo Derivatives in Their Keto and Leuco Forms

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