Investigation of the Redox and Acid‐Base properties of TCNQF and TCNQF₂: Electrochemistry, Vibrational Spectroscopy, and Substituent Effects

Abstract

The electrochemistry and acid-base chemistry of TCNQF and TCNQF 2 (TCNQ = 7,7,8, are described, and the results are compared to those reported previously for TCNQ and TCNQF 4 . In acetonitrile solution, both mono-and di-fluorinated TCNQ derivatives show two wellresolved, diffusion-controlled chemically and electrochemically reversible one-electron-transfer processes under the conditions of cyclic voltammetry. The reversible potentials of the monoand difluoro-TCNQ were determined for both the monoanionic and dianionic processes, that is, TCNQF 0/1À/2À and TCNQF 2 0/1À/2À . A Hammett plot shows a linear relationship of the potential differences between the three fluorinated derivatives and TCNQ with the sum of the Hammett constants for fluoro substitution. A significant positive shift in the reversible potential is found by increasing the number of fluoro substituents. Although the first TCNQF n 0/1À (n = 1,2) reduction process is not affected by addition of trifluoroacetic acid (TFA), the dianions are more basic and rapidly protonate to form H 2 TCNQF n . This explains the significant change detected in the electrochemistry of the second TCNQF n 1À/2À redox process. The addition of TFA to solutions of the monoanionic form also gives rise to the disproportionation of TCNQF n 1À to TCNQF n and H 2 TCNQF n , as proven electrochemically and spectroscopically. Furthermore, a higher number of fluoro substituents results in the reduced form of the molecule being more stable, as evidenced by both UV/Vis spectra and voltammetric measurements. Finally, we performed DFT calculations for TCNQF 2 and TCNQF 2 to produce a spectroscopic library of characteristic IR and Raman bands for these species. These data are used for comparisons with earlier calculations for TCNQF 4 , and we report the experimental and calculated infrared and Raman spectra for TCNQF and TCNQF 2 . The vibrational frequencies of the trifluorinated species, TCNQF 3 , were also calculated to complete the series.

Electrochemical Investigation of the Oxidation of Thiosulfate by 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane and Its Anion Radical

“…The large difference in oxidizing power is reflected in the fact that the formal reversible potentials are 0.310 V and À 0.220 V (vs Ag/Ag + ) for the TCNQF 4 0/1À and TCNQF 4 1À /2À half-cell reactions, respectively. [14][15] This study is focused on the thermodynamic and kinetic differences which arise when neutral TCNQF 4 0 or the negatively charged TCNQF 4 1À anion oxidize S 2 O 3 2À in 95 % MeCN : 5 % water. The product in both cases is identified as S 4 O 6 2À .…”

“…In this work, the range of oxidants explored has been extended to include TCNQF 4 0 , TCNQF 4 1− and TCNQF 4 2− . The high electron affinity of TCNQF 4 of 3.20 eV, [14] attributed to the electron‐withdrawing effects of fluoro‐groups makes TCNQF 4 0 a powerful organic oxidant. The large difference in oxidizing power is reflected in the fact that the formal reversible potentials are 0.310 V and −0.220 V (vs Ag/Ag + ) for the TCNQF 4 0/1− and TCNQF 4 1−/2− half‐cell reactions, respectively [14–15] …”

Diaminodicyanoquinones: Fluorescent Dyes with High Dipole Moments and Electron‐Acceptor Properties

“…[8] Only in the solid state are DADQs moderately emissive with QYs of up to 45 %. [9] Consequently,D ADQ derivatives are not considered as fluorescent dyes.C onformational relaxations can have ah igh impact on fluorescence, [10] as exploited, for example,for aggregation-induced emission, [11] where blocking these pathways is used to generate as ignal amplification or used as sensing principle for viscosity [12] and temperatureresponsive molecules. [10b, 13] Here we demonstrate that QYs in DADQs can be finetuned by adjusting the substitution pattern, such that QYs exceeding 90 %i sp ossible (see Figure 1).…”

Diaminodicyanochinone – Fluoreszenzfarbstoffe mit hohem Dipolmoment und Elektronenakzeptor‐Eigenschaften

“…[9] Folglich werden DADQ-Derivate nicht als Fluoreszenzfarbstoffe betrachtet. Ebenso kann eine Sensorik zur Bestimmung der Viskositäta ufgebaut [12] oder die temperaturabhängige Ansprechbarkeit von Molekülen ausgenutzt werden. B. in der aggregationsinduzierten Emission genutzt wird.…”

“…[11] Dabei kann das Blockieren der Konformationsrelaxationen zur Erzeugung einer Signalverstärkung genutzt werden. Ebenso kann eine Sensorik zur Bestimmung der Viskosität aufgebaut [12] oder die temperaturabhängige Ansprechbarkeit von Molekülen ausgenutzt werden. [10b, 13] In dieser Arbeit zeigen wir, dass die QY durch das Substitutionsmuster in DADQs gesteuert werden kann und QY von über 90 % mçglich sind (siehe Abbildung 1).…”