Direct Measurements of Intersystem Crossing Rates and Triplet Decays of Luminescent Conjugated Oligomers in Solutions

Chen, Hsin‐Liang; Huang, Yu-Ching; Hsu, Chao‐Ping; Lim, Tsong–Shin; Kuo, Li-Chung; Leung, M.‐k.; Chao, Teng‐Chih; Wong, Ken‐Tsung; Chen, Show‐An; Fann, Wunshain

doi:10.1021/jp0740651

Cited by 9 publications

(5 citation statements)

References 52 publications

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“…It has been demonstrated that the nonradiative rates in metal-based systems are governed by the energy gap law, although deviations from a well-defined relationship are observed for low band gap energies <2.4 eV. Moreover, significant deviations from the predicted relationship are also observed, 40,41 especially in the transition between monomeric and polymeric structures. 42 The nonradiative rate also shows a deviation from the predicted exponential relationships when dealing with complexes wherein the structure varies from a homologous complex.…”

Section: ■ Resultsmentioning

confidence: 99%

Influence of Auxiliary Ligands on the Photophysical Characteristics of a Series of Ruthenium(II)–Polypyridyl Complexes

O’Neill¹,

Perdisatt²,

O’Connor³

2012

J. Phys. Chem. A

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A series of ruthenium−polypyridyl complexes were studied using UV/vis absorption and luminescence spectroscopy as well as luminescence lifetime determination by time-correlated single photon counting (TCSPC). The complexes were characterized with regard to the variation in the electronic band gap as a result of the sequential variation of the auxiliary ligand 2,2′-bipyridine (bpy), 1,10phenanthroline (phen), and 2,2′-biquinoline (biq) ligands while the main ligand remained constant for three different main ligand types. Luminescence yields were calculated and correlated with structural and electronic variation. It was found that both the absorption and emission characteristics could be tailored through the systematic variation of the reduction potential of the individual auxiliary ligand. This was shown to be the case regardless of the functional group at the end of the main ligand. Stokes shift and Raman spectroscopy were employed as a means to gauge the effect of ligand change on the conjugation and vibrational characteristics of the complexes. Luminescence yield and lifetimes were also shown to be well-defined with regards to systematic structure variations. The well-defined trends established elucidate the effect which variation of auxiliary ligands has on the electronic and excited state characteristics of the ruthenium−polypyridyl systems. These well-defined relationships can potentially be extended to optimize luminescence yield and lifetimes and therefore suitability of such compounds for the application in for example photodynamic therapy.

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Section: ■ Resultsmentioning

confidence: 99%

Influence of Auxiliary Ligands on the Photophysical Characteristics of a Series of Ruthenium(II)–Polypyridyl Complexes

O’Neill¹,

Perdisatt²,

O’Connor³

2012

J. Phys. Chem. A

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“…In terms of heat relaxation, the PAC amplitude is proportional to the total yield of nonradiative decay paths, including intersystem crossing and internal conversion . For TSBF, it has been reported that the PAC amplitude (0.20, normalized with respect to HBP) is mainly contributed by internal conversion (ϕ IC = 0.09) and intersystem crossing (ϕ T = 0.06), whereas the contribution from volume change is negligible. , These fluorescence quantum yields (ϕ) of materials were measured at various concentrations by fluorescence spectrometer. Figure b shows the plot of integrated fluorescence intensity vs absorbance (varied by changing the solution concentration within the limit of 0.1 or less in optical density).…”

Section: Resultsmentioning

confidence: 99%

Excited-State Backbone Twisting of Polyfluorene As Detected from Photothermal After-Effects

et al. 2009

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By means of time-resolved photoluminescence and photothermal techniques, after-effects from excited-state dynamics, energy migration, and conformational rearrangement of poly(9,9-di-n-octyl-2,7-fluorene) (PFO) and its homologues has been examined and interpreted with rotational potential maps from quantum mechanical calculations. Steady-state photoluminescence spectral changes and time-resolved photoluminescence measurements of oligofluorenes and PFO diluted in toluene suggest excited state ring torsion occurring within 30 ps of photoexitation. With all effects from internal conversion/intersystem crossing processes properly accounted for, we show that the conformational changes associated with this twisting motion can be quantitatively probed by means of photothermal methods. Results suggest mean torsion between neighboring fluorene units by ca. 40 degrees upon excitation, in agreement with the shift of rotational potential minimum from +/-40 degrees (and +/-140 degrees) in the ground state to +/-20 degrees (and +/-160 degrees) in the first excited singlet state according to results of quantum mechanical calculations.

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“…It is anticipated that direct measurement of relative conjugation across the imidazole bridge via Raman spectroscopy will elucidate both the complex relationship shown earlier and shortcoming of the energy gap law [35][36][37] when considering monomer to polymeric structures [38,39]. Figure 7 shows the linear variation of the luminescence yield as a function of the variation of the frequency of the imidazole ring stretch of the polypyridyl ligand.…”

Section: Results: Part I-effect Of Changing Electron Affinity Of the mentioning

confidence: 97%

Structure-Property Relationships for a Series of Ruthenium(II) Polypyridyl Complexes Elucidated through Raman Spectroscopy

O’Neill¹,

Perdisatt²,

O’Connor³

2018

Journal of Spectroscopy

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A series of ruthenium polypyridyl complexes were studied using Raman spectroscopy supported by UV/Vis absorption, luminescence spectroscopy, and luminescence lifetime determination by time-correlated single photon counting (TCSPC). The complexes were characterised to determine the influence of the variation of the conjugation across the main polypyridyl ligand. The systematic and sequential variation of the main polypyridyl ligand, 2-(4-formylphenyl)imidazo[4,5-f][1,10]phenanthroline (FPIP), 2-(4-cyanophenyl)imidazo[4,5-f][1,10]phenanthroline (CPIP), 2-(4-bromophenyl)imidazo[4,5-f][1,10]phenanthroline (BPIP), and 2-(4-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline (NPIP) ligands, allowed the monitoring of very small changes in the ligands electronic nature. Complexes containing a systematic variation of the position (para, meta, and ortho) of the nitrile terminal group on the ligand (the para being 2-(4-cyanophenyl)imidazo[4,5-f][1,10]phenanthroline (p-CPIP), the meta 2-(3-cyanophenyl)imidazo[4,5-f][1,10]phenanthroline (m-CPIP) and 2-(2-cyanophenyl)imidazo[4,5-f][1,10]phenanthroline (o-CPIP)) were also characterised. Absorption, emission characteristics, and luminescence yields were calculated and correlated with structural variation. It was found that both the electronic changes in the aforementioned ligands showed very small spectral changes with an accompanying complex relationship when examined with traditional electronic methods. Stokes shift and Raman spectroscopy were then employed as a means to directly gauge the effect of polypyridyl ligand change on the conjugation and vibrational characteristics of the complexes. Vibrational coherence as measured as a function of the shifted frequency of the imizodale bridge was shown to accurately describe the electronic coherence and hence vibrational cooperation from the ruthenium centre to the main polypyridyl ligand. The well-defined trends established and elucidated though Raman spectroscopy show that the variation of the polypyridyl ligand can be monitored and tailored. This allows for a greater understanding of the electronic and excited state characteristics of the ruthenium systems when traditional electronic spectroscopy lacks the sensitivity.

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Direct Measurements of Intersystem Crossing Rates and Triplet Decays of Luminescent Conjugated Oligomers in Solutions

Cited by 9 publications

References 52 publications

Influence of Auxiliary Ligands on the Photophysical Characteristics of a Series of Ruthenium(II)–Polypyridyl Complexes

Influence of Auxiliary Ligands on the Photophysical Characteristics of a Series of Ruthenium(II)–Polypyridyl Complexes

Excited-State Backbone Twisting of Polyfluorene As Detected from Photothermal After-Effects

Structure-Property Relationships for a Series of Ruthenium(II) Polypyridyl Complexes Elucidated through Raman Spectroscopy

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