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

Abstract

This short critical review is devoted to the synthesis and functionalization of various types of azaacenes, organic semiconducting compounds which can be considered as promising materials for the fabrication of n-channel or ambipolar field effect transistors (FETs), components of active layers in light emitting diodes (LEDs), components of organic memory devices and others. Emphasis is put on the diversity of azaacenes preparation methods and the possibility of tuning their redox and spectroscopic properties by changing the C/N ratio, modifying the nitrogen atoms distribution mode, functionalization with electroaccepting or electrodonating groups and changing their molecular shape. Processability, structural features and degradation pathways of these compounds are also discussed. A unique feature of this review concerns the listed redox potentials of all discussed compounds which were normalized vs. Fc/Fc+. This required, in frequent cases, recalculation of the originally reported data in which these potentials were determined against different types of reference electrodes. The same applied to all reported electron affinities (EAs). EA values calculated using different methods were recalculated by applying the method of Sworakowski and co-workers (Org. Electron. 2016, 33, 300-310) to yield, for the first time, a set of normalized data, which could be directly compared.

Exploring Intermolecular Singlet Fission in Pyrene-Fused Azaacenes Film

“…25 Azaacenes offer greater stability than the corresponding acenes, and their energy levels can be easily adjusted by varying the number and position of the nitrogen atoms. 26,27 Beyond the methods mentioned above, another strategy could be the introduction of pyrene units into the framework of acenes or azaacenes. The cross-conjugation of pyrene units shows promise for improving stability and increasing length.…”

“…For instance, TIPS-pentacene exhibits comparable efficiency to pentacene, although its dynamics are slower (∼1 ps) compared with those of unsubstituted pentacene. − Furthermore, the insertion of nitrogen atoms into the backbone of acenes (called azaacenes) has been shown to accelerate the formation process of the triplet state . Azaacenes offer greater stability than the corresponding acenes, and their energy levels can be easily adjusted by varying the number and position of the nitrogen atoms. , Beyond the methods mentioned above, another strategy could be the introduction of pyrene units into the framework of acenes or azaacenes. The cross-conjugation of pyrene units shows promise for improving stability and increasing length. , Specifically, azaacenes incorporating one pyrene unit have been developed comprising ten aromatic rings in a line and with high stability in the air .…”

From unprecedented 2,2′-bisimidazole-bridged rare earth organometallics to magnetic hysteresis in the dysprosium congener

“…Moreover, the metal centers are symmetry-related through an inversion center residing on the bim C 2 –C′ 2 bond. In certain cases, the tetraphenylborate moiety within Cp* 2 RE(BPh 4 ) is able to reduce redox-active ligands innate to accessible redox potentials such as phenazine (−1.83 V vs. Fc/Fc + ), 41 and thus, could potentially undergo a redox reaction with bim 2− to produce a radical bridge with a 3 − ˙ oxidation state, where the an unpaired electron is localized in the ligands π*-orbitals. 42 However, the central C 2 –C′ 2 distance of 1.438(15) Å ( 1 ), 1.45(2) Å ( 2 ), and 1.448(4) Å ( 3 ), relative to 1.433(15) Å of the bim 2− -bridged diosmium complex [(Os II (bpy) 2 ) 2 (bim)](ClO 4 ) 2 , 14 as the structurally closest example, alluded to an unambiguous assignment of the bim oxidation state as −2 in 1–3 .…”

Azaacene containing iridium(iii) phosphors: elaboration of the π-conjugation effect and application in highly efficient solution-processed near-infrared OLEDs

“…10 Azaacenes (N-heteroacenes) are a class of heteroaromatic compounds and have been investigated for years, from their synthesis to applications. 11 By embedding sp 2 nitrogen into traditional acenes, the resulting azaacenes can exhibit different optoelectronic properties, such as the energy level, air stability and carrier transport. Therefore, various types of azaacenes are widely applied in organic thin-film transistors, solar cells and light-emitting diodes.…”