Effect of the fluorine substitution in ethyl groups of 1,4-distyrylbenzene on the fine structure fluorescence and fluorescence excitation spectra

Abstract

The fine structure fluorescence and fluorescence excitation spectra of conjugated chain com pounds, 1,4 distyrylbenzene (DSB) and its fluorine substituted derivative α,ω 1,4 distyrylbenzene, have been obtained by the Shpolskii method in an n octane matrix at a temperature of 4.2 K. These spectra have been simulated by representing the band of each of the vibronic transitions as the sum of a zero phonon line and a phonon wing with the corresponding parameters, such as the half widths of the spectral lines and the Debye-Waller factors. Based on this simulation, the relative intensities of vibronic transitions have been determined and the frequencies of normal vibrations in the S 0 and states have been refined. It has been found that the energy of the purely electronic transition in the molecule of the fluorine substituted derivative is higher by 950 cm -1 compared to the unsubstituted DSB. The parameters of the Franck-Condon and Herzberg-Teller interactions have been determined. The observed violation of the mirror symmetry between the conjugated spectra is explained by the interference of intramolecular interactions.

Highly Emissive H-Aggregates or Aggregation-Induced Emission Quenching? The Photophysics of All-Trans para-Distyrylbenzene

“…34 The absorption spectrum of DSB in solution is dominated by the intense S 0 (1 1 A g ) → S 1 (1 1 B u ) electronic transition (Figure 2), 34 essentially described by a transition between the highest occupied S1 in the SI). 38 High-resolution spectra at LT conditions 34,44 (recently done also under siteselective conditions 48 ) in combination with quantum chemical analysis 34 allowed for the determination of the prominent totally symmetrical vibrational modes, which couple to the electronic transition. 49 This gives rise to a reorganization energy ΔE ro (i.e., the difference of the vertical and adiabatic transition energies 50 ) of 0.26 eV; see Table 1.…”

“…The absorption spectrum of DSB in solution is dominated by the intense S 0 (1 1 A g ) → S 1 (1 1 B u ) electronic transition (Figure ), essentially described by a transition between the highest occupied and lowest unoccupied molecular orbitals (HOMO → LUMO), which is oriented fairly along the long molecular axis (defined by the connection of the terminal C-atoms, see Figure , that is, enclosing an angle of 2° in C 2 h ) as determined by TD-DFT-based calculations (see Table S1 in the SI). High-resolution spectra at LT conditions , (recently done also under site-selective conditions) in combination with quantum chemical analysis allowed for the determination of the prominent totally symmetrical vibrational modes, which couple to the electronic transition . This gives rise to a reorganization energy Δ E ro (i.e., the difference of the vertical and adiabatic transition energies) of 0.26 eV; see Table .…”

“Though It Be but Little, It Is Fierce”: Excited State Engineering of Conjugated Organic Materials by Fluorination

“…8,77 For instance, bathochromic shifts are found for ring substitution in oligoacenes (PFnAc), 18,43,78 rubrene, 79 porphyrins, 80 or polymers based on pyrrole 81 and phenylenevinylene repetition units (PPV). 82 Conversely, (substantial) hypsochromic shifts are observed upon direct fluorination of oligothiophenes (PFnT), 42,83 arene-thiophenes, 46 dithieno-benzothiadiazole, 84 oligofluorenes, 85 and oligophenylenes, 73 upon fluorination in the vinylene unit of p-distyrylbenzene (DSB), 86 as well as of MEHPPV-type oligomers and polymers, 70,87,88 or upon perfluoroalkyl-substitution of polythiophene (PT) 89 and PPV. 19 Small hypsochromic or even negligible shifts were observed for cyanine dyes.…”

“…Different from conventional substituents, fluorination of conjugated compounds can induce either hypso- (blue) or bathochromic (red) shifts of UV/vis absorption spectra, depending on the molecular backbone. , For instance, bathochromic shifts are found for ring substitution in oligoacenes (PF n Ac), ,, rubrene, porphyrins, or polymers based on pyrrole and phenylenevinylene repetition units (PPV) . Conversely, (substantial) hypsochromic shifts are observed upon direct fluorination of oligothiophenes (PF n T), , arene-thiophenes, dithieno-benzothiadiazole, oligofluorenes, and oligophenylenes, upon fluorination in the vinylene unit of p-distyrylbenzene (DSB), as well as of MEHPPV-type oligomers and polymers, ,, or upon perfluoroalkyl-substitution of polythiophene (PT) and PPV . Small hypsochromic or even negligible shifts were observed for cyanine dyes. ,, Multiple fluorination of oligoacenes, , azulene, hemicyanines, spirobifluorene, as well as ring-fluorination of PPV-type oligomers, ,,,, or perfluoro-substitution of phenyl-porphyrins induces batho- or hypsochromic shifts depending on the number and position of fluorine substituents.…”

Analysis of vibronic interactions in the molecules of cross-conjugated ketones

“…It greatly expands the possibilities for use of the fragmented approach to describe the fundamental bands of molecules [6,7,[11][12][13].…”