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

TL;DR

This paper introduces halogenated organic dyes as nanoscale electric field probes, demonstrating enhanced Stark effects through DFT calculations and synthesizing a new fluorinated molecule with promising properties for spectroscopy.

Contribution

It presents a novel approach using halogenated dyes for electric field probing at the nanoscale, including theoretical analysis and synthesis of new fluorinated molecules.

Findings

Fluorination increases dipole difference in molecules.

DFT calculations show enhanced Stark coefficients.

Synthesis and spectroscopy of 3-fluoroterrylene are reported.

Abstract

We propose using halogenated organic dyes as nanoprobes for electric field 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 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 synthesis of 3-fluoroterrylene and bulk spectroscopy of this compound in liquid and solid organic environments.