Cavity Ring-Down Spectroscopy of the Torsional Motions of 1,4-Bis(phenylethynyl)benzene

Greaves, Stuart J.; Flynn, Emma L.; Futcher, Emma L.; Wrede, Eckart; Lydon, Donocadh P.; Low, Paul J.; Rutter, Simon R.; Beeby, Andrew

doi:10.1021/jp054426h

Cited by 73 publications

(81 citation statements)

References 57 publications

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“…24,25 In general, transient absorption provides information on the time dependent response due to the population dynamics and/or conformational changes in the excited electronic states. However, any involvement of the Franck-Condon active vibrational modes remains invisible under the broad excited state absorption bands, which makes it difficult to elucidate the structural vibrations involved during the time dependent nuclear dynamics.…”

Section: Urls Measurementsmentioning

confidence: 99%

“…21,24 In the ground state, the rotational barrier around the sp 2 -sp CC single bond is very low; it was determined by Greaves et al to be 220-235 cm 1 from a jet spectroscopy experiment, and this number agrees with the AM1 calculations of Levitus (0.5 kcal/mol = 180 cm 1 ). 25,26 Therefore, all rotamers ranging from planar to twisted forms are likely to co-exist at room temperature, resulting in electronic transitions at different energies. However, in the excited state, the energy difference between the planar and the twisted conformation is believed to be much larger: 15 kcal/mol.…”

Section: Introductionmentioning

confidence: 99%

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Mode specific excited state dynamics study of bis(phenylethynyl)benzene from ultrafast Raman loss spectroscopy

Roy

Kayal

Ariese

et al. 2017

The Journal of Chemical Physics

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Femtosecond transient absorption (fs-TA) and Ultrafast Raman Loss Spectroscopy (URLS) have been applied to reveal the excited state dynamics of bis(phenylethynyl)benzene (BPEB), a model system for one-dimensional molecular wires that have numerous applications in opto-electronics. It is known from the literature that in the ground state BPEB has a low torsional barrier, resulting in a mixed population of rotamers in solution at room temperature. For the excited state this torsional barrier had been calculated to be much higher. Our femtosecond TA measurements show a multi-exponential behaviour, related to the complex structural dynamics in the excited electronic state. Time-resolved, excited state URLS studies in different solvents reveal mode-dependent kinetics and picosecond vibrational relaxation dynamics of high frequency vibrations. After excitation, a gradual increase in intensity is observed for all Raman bands, which reflects the structural reorganization of Franck-Condon excited, non-planar rotamers to a planar conformation. It is argued that this excited state planarization is also responsible for its high fluorescence quantum yield. The time dependent peak positions of high frequency vibrations provide additional information: a rapid, sub-picosecond decrease in peak frequency, followed by a slower increase, indicates the extent of conjugation during different phases of excited state relaxation. The CC triple (–C≡C–) bond responds somewhat faster to structural reorganization than the CC double (>C=C<) bonds. This study deepens our understanding of the excited state of BPEB and analogous linear pi-conjugated systems and may thus contribute to the advancement of polymeric “molecular wires.”

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Section: Urls Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mode specific excited state dynamics study of bis(phenylethynyl)benzene from ultrafast Raman loss spectroscopy

Roy

Kayal

Ariese

et al. 2017

The Journal of Chemical Physics

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“…[5][6][7][8] Different research groups have investigated the use of PAEs and hyperbranched PAEs as molecular wires, OLEDs, OSCs, OTFTs and fluorescent chemical sensors. [9][10][11][12][13][14] The interesting electronic properties exhibited by PAEs can be related to the axial symmetry of ethynylene groups, which allows to maintain the conjugation (note that between adjacent aryl groups at different relative orientations rotational barriers are as small as 1 kcal mol -1 in these cases) [15][16][17][18][19][20] across the whole molecular backbone.…”

Section: Introductionmentioning

confidence: 99%

Optoelectronic and Semiconducting Properties of Conjugated Polymers Composed of Thiazolo[5,4-d]thiazole and Arene Imides Linked by Ethynylene Bridges

et al. 2016

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A set of engineered crystalline polymers containing thiazolo [5,4-d]thiazole and arene imides linked by ethynylene bridges have been modelled by means of Density Functional Theory (periodic boundary) calculations. A large set of relevant electronic properties related to the opto-electronic and semiconductor character of these systems, such as optical band gap, frontier molecular orbital energy levels, electron affinity, ionization potential, reorganization energy, and electronic coupling between neighboring polymer chains were obtained. We further discuss the effect of the ethynylene linkages, the presence of heteroatoms in thiazolo [5,4-d]thiazole rings, and

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“…17 The increase in the delocalization of the LUMO orbital could be achieved by the introduction of ethynylene groups (-C≡C-) as a bridge between the three aromatic rings; in fact the ethynylene group, due to its axial symmetry, could allow to extend the conjugation to adjacent arylene groups. [27][28][29][30][31][32] Note also that the actual synthesis of s-tetrazine ethynylene derivatives is possible through cross-coupling reactions on some s-tetrazine compounds (compounds a and b in Chart 1), as shown by Novák and Kotschy, 33 though we are not aware of any attempt for (ArCC) 2 Tz compounds.…”

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confidence: 99%

Bis(arylene-ethynylene)-s-tetrazines: A Promising Family of n-Type Organic Semiconductors?

et al. 2015

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We theoretically describe in this work the n-type semiconducting behavior of a set of bis(arylene-ethynylene)-s-tetrazines ((ArCC) 2 Tz), by comparing their electronic properties with those of their parent diaryl-s-tetrazines (Ar 2 Tz) after the introduction of ethynylene bridges. The significantly reduced internal reorganization energy for electron transfer is ascribed to an extended delocalization of the LUMO for (ArCC) 2 Tz as opposite to that for Ar 2 Tz, which was described mostly localized on the s-tetrazine ring. The largest electronic coupling and the corresponding electron transfer rates found 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 for bis(phenyl-ethynylene)-s-tetrazine, as well as for some halogenated derivatives, are comparable to those reported for the best performing n-type organic semiconductors materials such as diimides and perylenes. The theoretical mobilities for the studied compounds turn out to be in the range 0.3 -1.3 cm 2 V −1 s −1 , close to values experimentally determined for common n-type organic semiconductors used in real devices. In addition, ohmic contacts can be expected when these compounds are coupled to metallic cathodes such as Na, Ca and Sm. For these reasons, the future application of semiconducting bis(phenyl-ethynylene)-s-tetrazine and its fluorinated and brominated derivatives in optoelectronic devices is envisioned.

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Cavity Ring-Down Spectroscopy of the Torsional Motions of 1,4-Bis(phenylethynyl)benzene

Cited by 73 publications

References 57 publications

Mode specific excited state dynamics study of bis(phenylethynyl)benzene from ultrafast Raman loss spectroscopy

Mode specific excited state dynamics study of bis(phenylethynyl)benzene from ultrafast Raman loss spectroscopy

Optoelectronic and Semiconducting Properties of Conjugated Polymers Composed of Thiazolo[5,4-d]thiazole and Arene Imides Linked by Ethynylene Bridges

Bis(arylene-ethynylene)-s-tetrazines: A Promising Family of n-Type Organic Semiconductors?

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