Helicene Appended Benzothiadiazoles as Chiral Emitters.
Kévin MartinTal AharonMaurizio Mastropasqua TalamoAndreas HauserThomas BuergiNicolas VanthuyneMarco CaricatoNarcis AvarvariPublished in: Chemistry (Weinheim an der Bergstrasse, Germany) (2024)
A homologous series of 4,7-bis(aryl) substituted benzothiadiazole (BTD) compounds, containing the helicenic derivatives bis([4]helicene), bis([5]helicene) and bis([6]helicene), have been prepared upon a double Suzuki coupling between 3,6-bis(pinacolyl-borane)-BTD and the corresponding bromo-aryl precursors. The single crystal X-ray structure of the bis([4]helicene) compound shows the existence of both helicities (M) and (P) on the same molecule. All the compounds of the series are highly emissive in solution, with quantum yields of the emission ranging from 50 to 91 %. The enantiopure compounds (M,M) and (P,P) for the BTD-bis([6]helicene) have been prepared from the corresponding enantiopure 2-bromo-[6]helicene precursors. Their chiroptical properties have been investigated in correlation with density functional theory (DFT) calculations, which allowed to confidently assign the absolute configuration of the helicene arms and to characterize the different electronic transitions, including the low energy charge transfer excitation from helicenes to BTD. The enantiomerically pure fluorophores (M,M)- and (P,P)-BTD-bis([6]helicene), which exist in solution as two main conformers, according to the DFT calculations, show CPL activity in solution, with g lum factors of ≈1.7×10 -3 at λ em =525 nm, and also in the solid state, with g lum factors of ≈1.2×10 -3 in spite of the strong decrease of the quantum efficiency.
Keyphrases
- density functional theory
- ionic liquid
- molecular dynamics
- solid state
- room temperature
- molecular docking
- molecular dynamics simulations
- oxidative stress
- magnetic resonance
- computed tomography
- monte carlo
- dna repair
- crystal structure
- quantum dots
- energy transfer
- dual energy
- single molecule
- contrast enhanced
- capillary electrophoresis