Peri‐Decoration of a Tetraazaperylene with Urea Units: Chiral Octaazaperopyrenedioxides (OAPPDOs) and Their Optical and Chiroptical Properties

Abstract

Octaazaperopyrenedioxides (OAPPDOs) are a new class of fluorescent polycyclic aromatic hydrocarbons based on a tetraazaperylene core that is formally condensed with N‐substituted urea units in the two opposite peri positions. Here, we report the synthesis of series of substituted OAPPDO derivatives with different N‐substitution patterns (H, alkyl, benzyl) in the peri positions, including bay‐chlorinated OAPPDOs. Starting from the latter, a series of bay‐arylated OAPPDOs was synthesized by Suzuki cross coupling, which resulted in the formation of helically chiral OAPPDO derivatives. The electrochemical and photophysical properties were investigated by UV/Vis and fluorescence spectroscopy as well as cyclic voltammetry. The P and M enantiomers of a phenylated OAPPDO were separated by semipreparative HPLC and further analyzed by CD spectroscopy. The frontier orbital energies, the mechanism of the isomerization, the electronic excitation and the CD spectrum (TD‐DFT) were computed and compared to the experimental data. The reversible 1e− oxidation of the OAPPDOs generates the corresponding radical cations, one of which was characterized by EPR spectroscopy. The reversible oxidation process was also systematically investigated by spectro‐electrochemistry.

Peri‐Functionalized Tetraazaperylenes: Strong Emitters for Molecular Polaritonics

“…The perchlorinated tetraazaperylene 1 , previously employed in the preparation of OAPP and OAPPDO dyes,[ 41 , 42 ] is a synthetically useful starting compound in the development of tetraazaperylene chemistry which allows the selective nucleophilic substitution of the four peri positions. To prepare the thioether‐functionalized derivatives 2 a – e , the corresponding in situ generated thiolates were reacted with 1 to give the desired thioether derivatives in good yields (Scheme 1 , middle).…”

“…We have recently begun to investigate the photophysical properties of tetraazaperylene derivatives in which the central N‐heteropolycycle provides the core for new classes of highly emissive and redox active functional dyes. [ 41 , 42 ] The peri (Y) and bay (X) positions may be modified independently via nucleophilic substitution and/or metal catalysed coupling reactions (Figure 1 ). To date, their potential as fluorophores has been studied for two classes of dyes derived from tetraazaperylene, the octaazaperopyrenes (OAPPs) [41] as well as the octaazaperopyrenedioxides (OAPPDOs).…”

“…To date, their potential as fluorophores has been studied for two classes of dyes derived from tetraazaperylene, the octaazaperopyrenes (OAPPs) [41] as well as the octaazaperopyrenedioxides (OAPPDOs). [42] For these compounds, the peri‐capping units may be viewed as formally condensed pyrimidine rings for the OAPPs and N‐substituted urea units for the OAPPDOs. These proved to provide limited structural variability with significant impact on the electronic structures of these compounds which is why we decided to pare back the structures and focus on the direct functionalization of the tetraazaperylene core (Figure 1 ).…”

Zipping up tetraazaperylene: synthesis of tetraazacoronenes via double coupling in the bay positions

“…This has led, inter alia , to a facile synthetic route to tetraazaperylenes, 19 octaazaperopyrenes 20 and octaazaperopyrenedioxides (OAPPDOs). 21 The latter can be seen as inversely peri-substituted aza-PDIs with urea- instead of imido-units. Their conversion to tetraazacoronenes was expected to significantly alter their properties as functional dyes, as observed for the parent coronene in relation to its perylene core.…”

“…The precursor of the tetraazacoronene synthesis was the previously reported bay-chlorinated OAPPDO 1 , 21 which was reacted with various symmetric bis(pinacolatoboryl)alkenes as C 2 -synthons in a double Suzuki–Miyaura cross coupling reaction (Scheme 1). Both para -phenyl substituted bis(pinacolatoboryl)-alkenes with electron donating and withdrawing substituents and ( Z )-2,2′-(oct-4- ene -4,5-diyl)bis(pinacolatoboryl) as an aliphatic example were chosen.…”