Journal Article

PUBDB-2025-00598

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png $(BO)_2$-doped tetrathia[7]helicenes: synthesis and property-change induced by “BO bond inversion”

Menduti, L. (Corresponding author) ; Baldoli, C. ; Manetto, S. ; Villani, C. ; Penconi, M. ; Grecchi, S. ; Arnaboldi, S. ; Mazzeo, G. ; Longhi, G. ; Bolte, M. ; Virovets, A.Extern* ; Lerner, H.-W. ; Wagner, M. (Corresponding author)Extern* ; Licandro, E.

2025
RSC Cambridge

This record in other databases:      

Please use a persistent id in citations: doi:10.1039/D4QO01897D  doi:10.3204/PUBDB-2025-00598

Abstract: Helical distortion of polyaromatic hydrocarbons gives rise to a special class of π-conjugated systems, namely helicenes. Owing to their configurational stability and easily tunable optoelectronic properties (via heteroatom-doping), helicenes have recently come to the fore as building blocks for applications in materials science (CP-OLEDs, chiroptical switches). In this context, boron-doped helicenes are particularly promising. Herein, we report the synthesis of the new (BO)2-doped tetrathia[7]helicene 2, derived by the formal inversion of (Mes)B–O moieties in the (previously reported) isomer 1. Theoretical characterization of 2, and comparison with 1, revealed that the inversion of the BO vectors promotes the extension of the LUMO via the central thiophene–benzene–thiophene fragment (and not via the terminal thiophene rings, as in 1), resulting in a considerable lowering of the LUMO energy (ELUMO(2) = −2.22 eV vs. ELUMO(1) = −1.65 eV). Spectroscopic studies revealed that the “BO bond inversion” also contributes to the narrowing of the energy gap (Eoptg (2) = 2.90 eV vs. Eoptg (1) = 3.16 eV) and causes a significant red-shift of the absorption/emission bands (≈40 nm). Interestingly, besides low fluorescence quantum yield (ΦPL(2) = 7%), 2 shows detectable circularly polarized luminescence (glum = 0.8 × 10−3) and pronounced phosphorescence at low temperature (77 K). (P)-/(M)-enantiomers of 2 were successfully separated by CSP-UHPLC and proved to be stable (ΔG‡enant = 29.4 ± 0.1 kcal mol−1 at 353 K). Racemization studies combined with theoretical calculations confirmed that BO-doping is an extremely perturbative tool for tuning the mechanical rigidity of tetrathia[7]helicenes (ΔG‡enant (2) is 10 kcal mol−1 lower than ΔG‡enant (7TH)).

---

Contributing Institute(s):

1. FS DOOR-User (FS DOOR-User)

Research Program(s):

1. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
2. FS-Proposal: I-20231044 (I-20231044) (I-20231044)

Experiment(s):

1. PETRA Beamline P24 (PETRA III)

Appears in the scientific report 2025

---

Database coverage:
; ; ; Chemical Reactions ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Essential Science Indicators ; IF >= 5 ; Index Chemicus ; JCR ; National-Konsortium ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

---