Design and synthesis of aromatic molecules for probing electric fields at the nanoscale.

We propose using halogenated organic dyes as nanoprobes for electric fields and show their greatly enhanced Stark coefficients using density functional theory (DFT) calculations. We analyse halogenated variants of three molecules that have been of interest for cryogenic single molecule spectroscopy: perylene, terrylene, and dibenzoterrylene, with the zero-phonon optical transitions at blue, red, and near-infrared. Out of all the combinations of halides and binding sites that are calculated, we have found that fluorination of the optimum binding site induces a dipole difference between the ground and excited states larger than 0.5 D for all three molecules with the highest value of 0.69 D for fluoroperylene. We also report on the synthesis of 3-fluoroterrylene and the bulk spectroscopy of this compound in liquid and solid organic environments.