2,7-Diazapyrenes: a brief review on synthetic strategies and application opportunities

Abstract

This review discusses the synthetic routes for 2,7-diazapyrene derivatives and highlights the opportunities for application of 2,7-diazapyrenes, including their remarkable photophysical and supramolecular properties, in sensors and related areas.

Eclipsed and Twisted Excimers of Pyrene and 2-Azapyrene: How Nitrogen Substitution Impacts Excimer Emission

“…As the quest for appealing and adaptable organic materials continues, the design of π-conjugated polycyclic (hetero)aromatic hydrocarbons has emerged as a prominent subject of interest in the field of materials science. Since the 16π-electron conjugated polycyclic hydrocarbon exhibits desirable electronic and photophysical properties, doping the pyrene core with more electronegative atoms, like nitrogen, has become a novel efficient strategy for fine-tuning such properties [ 19 , 20 , 21 , 22 , 23 , 24 ]. The introduction of a nitrogen atom in place of a carbon within a peri-fused pyrene framework brings about a substantial modification and enhancement of the properties, leading to novel and diverse applications as materials in organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs) and organic field-effect transistors (OFETs) [ 25 ].…”

Synthesis and Properties of Thieno[2′,3′,4′:4,5]naphtho[1,8-cd]pyridines

“…We recently reported a convenient and broadly applicable Brønsted acid-mediated alkyne-benzannulation strategy for the synthesis of 1- and 2-azapyrenes functionalized at the generally synthetically challenging 5-, 9-K-region and 7-nodal plane positions. , The pyridine-type N-atoms in aza-pyrenes have been shown to stabilize the energy levels of the Frontier molecular orbitals (FMOs), enhance the electron accepting ability, increase the conjugation with peripheral substituents, and significantly affect the excited state dynamics (e.g., the fluorescence quantum yield, lifetime, and electronic state mixing of the two lowest excited states). Moreover, the pyridine nitrogen introduces additional features, like hydrogen bonding, protonation, metal coordination, possible quaternization, and supramolecular self-assembly properties. − On the other hand, ullazine, which is isoelectronic to pyrene and bears a pyrrole-type N-atom, has received much attention as a photosensitizer in dye-sensitized solar cells, owing to its strong donor properties, which result from a unique 14π-electron charge-separated structure. − The introduction of an additional pyridine-type nitrogen atom in position 6 of the ullazine core leads to nearly identical optoelectronic properties. , At the same time, the incorporation of boron–nitrogen (BN), boron–oxygen (BO) or mixed BN/BO units into the ullazine scaffold leads to distinct effects on the aromaticity and FMO energy levels, which result in larger band gaps and, hence, blue-shifted absorption and emission. These boron-doped ullazines are also expected to find potential application in UV (ultraviolet)-organic light-emitting devices. , In contrast, the presence of BN units within the pyrene skeleton results in lower band gaps with strongly redshifted absorption and emission and prevents excimer formation. − Thus, the incorporation of heteroatoms of different natures and their effects within the π-conjugated framework is an important field of study to understand structure–property relationships.…”