Triplet state dynamics on isolated conjugated polymer chains

Burrows, Hugh D.; Melo, J. Sérgio Seixas de; Serpa, Carlos; Arnaut, Luı́s G.; Miguel, Maria; Monkman, Andrew P.; Hamblett, I.; Navaratnam, S.

doi:10.1016/s0301-0104(02)00684-5

Cited by 103 publications

(108 citation statements)

References 62 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].…”

Section: Absorptionmentioning

confidence: 61%

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: 61%

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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“…31 Triplet sate formation of BPHF was not observed when acridine (1.97 eV), 9-fluorenone (2.19 eV), or benzil (2.31 eV) were used as sensitizers showing that the triplet energy of this cruciform lies above these. 15 With chrysene (2.48 eV), 15 we were unable to induce the BPHF triplet state, but in this particular case, analysis was difficult because the transient absorption spectra of these two samples are very close.…”

Section: Resultsmentioning

confidence: 98%

Excited State Properties of Oligophenyl and Oligothienyl Swivel Cruciforms

et al. 2008

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A comprehensive study has been undertaken of the electronic spectral and photophysical properties of two oligophenyl (BPH and BPHF) and one oligothienyl (BTF) swivel cruciforms involving measurements of absorption, fluorescence, and phosphorescence spectra, quantum yields of fluorescence (φ F ), phosphorescence (φ Ph ) and triplet formation (φ T ), lifetimes of fluorescence (τ F ) and of the triplet state (τ T ), and quantum yields of singlet oxygen production (φ ∆ ). From these, all radiative k F and radiationless rate constants, k IC and k ISC , have been obtained in solution. The energies of the lowest lying singlet and triplet excited states were also determined at 293 K. Several of the above properties have also been obtained at low temperature and in the solid state (thin films). In general, for the phenyl oligophenyl (BPH) and for the oligothienyl (BTF) compounds, the radiationless decay channels (φ IC + φ ISC ) are the dominant pathway for the excited-state deactivation, whereas with the fluorene based oligophenyl BPHF the radiative route prevails. In contrast to the general rule found for related oligomers (and polymers) where radiative emission from T 1 is absent, with the compounds studied, phosphorescence has been observed for all of the compounds, indicating that this type of functionalization can lead to emissive triplets. Time-resolved fluorescence decays with picosecond resolution revealed multiexponential (bi-and triexponential) decay laws compatible with the existence of more than one species or conformation in the excited state. These results are discussed on the basis of conformational flexibility in the excited state.

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“…A rather comprehensive study of alkene triplet energies was done by Caldwell and co-workers, and permitted to assess the energy differences between relaxed and spectroscopic triplets [23][24][25]. We have also used this technique to study the triplet energies of organic polymers [26,27], the enthalpy of electron transfer reactions [22,28], and of the photocyclization of phenylamines [29,30].…”

Section: Photoacoustic Calorimetrymentioning

confidence: 99%

(More) About biphenyl first excited triplet state energy

Gomes

Serpa

Arnaut

2006

Journal of Photochemistry and Photobiology A: Chemistry

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Biphenyl photophysics was extensively studied in the past and much attention was given to the measurement of its first excited triplet state energy. Phosphorescence and the corresponding T 1 ← S 0 absorption give triplet energies that differ by 10 kcal mol −1 . We revisited biphenyl photophysics using photoacoustic calorimetry (PAC), a technique that directly measures the thermochemistry and kinetics of short-lived transients in solution. PAC measurements give the relaxed biphenyl triplet energy of 67.8 ± 0.6 kcal mol −1 ; 2.3 kcal mol −1 higher than the spectroscopic value. The direct measurement of the biphenyl relaxed triplet energy reported in this work should resolve the continued misuse of its spectroscopic energy, in particular in the growing field of polyphenylene polymers.

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Triplet state dynamics on isolated conjugated polymer chains

Cited by 103 publications

References 62 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

Excited State Properties of Oligophenyl and Oligothienyl Swivel Cruciforms

(More) About biphenyl first excited triplet state energy

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