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

Abstract

Fluorination is frequently used to significantly change the properties of conjugated organic materials due to fluorine's exceptional properties; well-known is its impact on electronic structure, but it also impacts the geometry despite fluorine's small size. Less known, the changes in the electronic and geometrical properties may provoke drastic changes of the excited state properties like batho- and hypsochromic shifts of absorption and emission bands (inter alia leading to excited state switching), hypo- and hyperchromic effects, spectral broadening, and changes of the nonradiative deactivation pathways. The state of the art on these issues is summarized in the current Perspective to stimulate further discussions on this intriguing subject.

Concurrent Optical Gain Optimization and Electrical Tuning in Novel Oligomer:Polymer Blends with Yellow‐Green Laser Emission

“…[30,31] These oligomers all share similar properties regardless their side substituents: they possess deep-blue fluorescence, relatively high PLQE, and outstanding thermal stability with T d and T g temperatures exceeding 380 and 150 °C, respectively (see Figure S2, Supporting Information). The absorption and PL spectra of DF and DCF3 confirm that F and CF 3 fluorination lead to a moderate absorption and PL redshift, [33,34] with absorption (PL) maxima at 309 (394) nm, 309 (403) nm, and 308 (414) nm for DPHS, DF, and DCF3, respectively. The PLQE values of DF/F8BT blends, selected for a detailed study, reflect a twofold increase with respect to that of F8BT, highlighting the beneficial effects of host dilution and energy transfer.…”

PAH/PAH(CF3)n Donor/Acceptor Charge‐Transfer Complexes in Solution and in Solid‐State Co‐Crystals

“…20 mg (3.5 %b ased on ANTH). The 1 Ha nd 19 FNMR spectra of ANTH-6-2 ( Figure S1 in Supporting Information) demonstrated that the purity of ANTH-6-2 was 98 + mol %.…”

“…Ta ble S1 in SupportingI nformation lists all PAH(CF 3 ) n compounds reported in the literature to date (i.e.,c ompounds with at least two fused aromatic rings with 0, 1, or 2Natoms, one or more CF 3 groups, and no other substituents), including the new electron acceptors ANTH-6-2 and PYRN-6-2 reported here for the first time. The 1 Ha nd 19 FNMR spectra of ANTH-6-2 and PYRN-6-2 are shown in Figures S1 and S2, respectively.The cyclic voltammograms of ANTH-6-2, PYRN-6-2, and CORO are shown in Figure S3. The recently published UV spectra of ANTH and ANTH-6-1 are shown in Figure S4.…”

Evaluating the Impact of Fluorination on the Electro-optical Properties of Cross-Conjugated Benzobisoxazoles

“…12 The small atomic radius of fluorine is minimally disruptive on the structure, but the polar nature of the carbon-fluorine bond increases the dipole moment, modifies the intramolecular interactions, and potentially enhances charge transport. 13,14 Furthermore, the quadrupole moments of perfluorinated acenes are opposite in sign of the analogous acenes, thus significantly tuning the orbital energetics and intermolecular overlaps. [15][16][17] Most interestingly, fluorination has been shown to greatly impact the optical transitions of conjugated organic molecules, however, the nature of this modification varies depending on the nature of the molecule.…”

“…[15][16][17] Most interestingly, fluorination has been shown to greatly impact the optical transitions of conjugated organic molecules, however, the nature of this modification varies depending on the nature of the molecule. 14,18 For example, in comparison to the corresponding non-fluorinated derivatives, bathochromic shifts in the absorption spectra were observed for fluorinated oligothiophenes, 19 while hypsochromic shifts were seen for oligoacenes. 12,18 In this work, we evaluated the impact of fluorine substitution on a series of benzo [1,2d:4,5-d′]bisoxazole (BBO)-based cruciforms (Chart 1).…”