Exploration of the Photodegradation of Naphtho[2,3‐g] quinoxalines and Pyrazino[2,3‐b]phenazines

Abstract

Nitrogen-containing polycyclic aromatic hydrocarbons are very attractive compounds for organic electronics applications. Their low-lying LUMO energies points towards a potential use as n-type semiconductors. Furthermore, they are expected to be more stable under ambient conditions, which is very important for the formation of semiconducting films, where materials with high purity are needed. In this study, the syntheses of naphtho[2,3-g]quinoxalines and pyrazino[2,3-b]phenazines is presented by using reaction conditions, that provide the desired products in high yields, high purity and without time-consuming purification steps. The HOMO and LUMO energies of the compounds are investigated by cyclic voltammetry and UV/Vis spectroscopy and their dependency on the nitrogen content and the terminal substituents are examined. The photostability and the degradation pathways of the naphtho[2,3-g]quinoxalines and pyrazino[2,3-b]phenazines are explored by NMR spectroscopy of irradiated samples affirming the large influence of the nitrogen atoms in the acene core on the degradation process during the irradiation. Finally, by identifying the degradations products of 2,3-dimethylnaphtho[2,3-g]quinoxaline it is possible to track down the most reactive position in the compound and, by blocking this position with nitrogen, to strongly increase the photostability.

A Versatile Approach for In Situ Monitoring of Photoswitches and Photopolymerizations

“…Alternatively, direct illumination and monitoring has been accomplished within an NMR spectrometer,e ither by installing al ight source inside the instrumento ru sing an optical fiber,w hich typically requires probe modificationo racoaxial glass insert, respectively. [31][32][33][34][35][36][37][38][39][40][41][42][43] The use of light-coupled optical fibers with NMR spectroscopy has distinct advantages from the standpoint of technical simplicity,c ompatibility with aw ide radiation range (UV-IR), and relativelyl ow cost (comparedt op robe modifications). Apart from traditional coaxial capillaryi nserts, "pencil tip" inserts [38,39] and fiber-tipe tching procedures [31,33] have been utilized to pro-As imple, inexpensive, and modularm ethod to directly illuminate NMR samples for in situ analysis of photochemical transformations is reported.T he versatility of this technique is demonstrated by analyzing the light-induced propagating front for small-molecule photoswitchesa nd the kinetics of photocontrolled living radical polymerizations.…”

“…Moreover, removing aliquots from a reaction can lead to contamination (e.g., oxygen) and continually decreases the volume of the system. Alternatively, direct illumination and monitoring has been accomplished within an NMR spectrometer, either by installing a light source inside the instrument or using an optical fiber, which typically requires probe modification or a coaxial glass insert, respectively . The use of light‐coupled optical fibers with NMR spectroscopy has distinct advantages from the standpoint of technical simplicity, compatibility with a wide radiation range (UV–IR), and relatively low cost (compared to probe modifications).…”

Azaacenes Based Electroactive Materials: Preparation, Structure, Electrochemistry, Spectroscopy and Applications—A Critical Review

“…This is associated with their significantly higher IP values. Detailed studies of the degradation of naphtho[2,3- g ]quinoxalines and pyrazino[2,3- b ]phenazines showed that the degradation starts by oxidation of three rings to their peroxide form and then their further transformation to quinones [ 75 ]. The terminal ring turned out to be the most resistant in this process whereas the degradation process started by oxidation of the ring adjacent to it.…”

The Direct Synthesis of Imines, Benzimidazoles and Quinoxalines from Nitroarenes and Carbonyl Compounds by Selective Nitroarene Hydrogenation Employing a Reusable Iron Catalyst

“…[11] Thus, the development of novel imine synthesis protocols is of high interest. [7,12,13] Benzimidazoles [7,14] and quinoxalines [15] are similarly important as well as the developmento fp rotocols for their synthesis. We have recently introduced av ariety of SiCN-metal nanocomposite catalysts [16] and have, very recently,i ntroduced highly active,s elective and reusablec obalt catalysts.…”

“…The reactionc onditions for 1-iodo-4-nitrobenzene (Table 1; entry 9), had to be modified slightly.O therh ydrogenation-sensitive functional groups,s uch as aldehydes, amides, ketones, and nitriles, could be tolerated too ( Table 1). The temperaturea nd the pressure were slightly increased to ensure full conversion of sterically more demanding substrates (Table 1; entries [15][16][17]. We also investigated (E)-(2-nitrovinyl)benzene but observed am ixture of products since the CÀCd ouble bond was hydrogenated.H eterocyclic nitro compounds work as well as demonstrated for isoquinolin-5-amine (Table 1, entry 18).…”