Double Heterohelicenes Composed of Benzo[b]- and Dibenzo[b,i]phenoxazine: A Comprehensive Comparison of Their Electronic and Chiroptical Properties

Abstract

Heterohelicenes are potential materials in molecular electronics and optics because of their inherent chirality and various electronic properties originating from the introduced heteroatoms. In this work, we comprehensively investigated two kinds of double NO-hetero[5]helicenes composed of 12Hbenzo[b]phenoxazine (BPO) and 13H-dibenzo[b,i]phenoxazine (DBPO). These helicenes exhibit good electron-donor properties reflecting the electronrich character of their monomers and were demonstrated to work as p-type semiconductors. The enantiomers of these helicenes show the largest class of dissymmetry factors for circularly polarized luminescence (CPL) (|g CPL | > 10 −2 ) among helicenes reported to date. Interestingly, the signs of CPL are opposite for BPO and DBPO double helicenes of the same helicity. The origin of the large g CPL values and the inversion of the CPL sign was addressed by analysis of the transition electronic dipole moments and transition magnetic dipole moments based on TD-DFT calculations.

The Scholl Reaction as a Powerful Tool for Synthesis of Curved Polycyclic Aromatics

“…The regioselective C–N bond formation in 121a – c is explained on the basis of the fact that the radical cation of 120a – c has the largest spin density on this particular carbon. Under the same conditions, 119 was synthesized in a yield of 69% by oxidation of 123 , which was synthesized by oxidation of 12 H -benzo­[ b ]­phenoxazine ( 122 ) with 0.5 equiv of DDQ . Both 118b and 119 exist in the crystals as a racemic mixture of ( P , P ) and ( M , M ) stereoisomers.…”

π‐Extendedperi‐Acenes: Recent Progress in Synthesis and Characterization

“…In addition, the energy gap of 64 b (2.83 eV), estimated by the absorption spectroscopy, was higher than [4,2]PA (1.1 eV). Recently, NO‐doped bistetracene ( 68 ) was synthesized and its optoelectronic properties were investigated [77] . Towards the synthesis, 12 H ‐benzo[ b ]phenoxazine ( 66 ) was treated with DDQ and the obtained cruciform dimer 67 was converted into 68 in 69 % yield in the presence of DDQ and Sc(OTf) 3 (Figure 17e).…”

“…Recently, NOdoped bistetracene ( 68) was synthesized and its optoelectronic properties were investigated. [77] Towards the synthesis, 12Hbenzo[b]phenoxazine (66) was treated with DDQ and the obtained cruciform dimer 67 was converted into 68 in 69 % yield in the presence of DDQ and Sc(OTf) 3 (Figure 17e). The molecular structure of 68 was unambiguously confirmed by X- ray crystallography (Figure 17f).…”

Recent Advances in Multiple Heterohelicenes

“…The same group synthesized O-doped double [5]helicenes 34 in 2021 using a similar synthetic process. [58] The inclusion of an extra fused benzene ring, resulting in more prolonged-conjugation, explained the red-shifted absorption of 33c when compared to 34.…”

“…(a, b,c, d, e) Reproduce from ref [57]. (f, g) Reproduce from ref.,[58] Copyright (2021), with permission from American Chemical Society.…”