  We demonstrate the potential of perylene bisimide (PBI) for label-free
sensing of organic molecules by investigating the change in electronic
properties of five symmetric and asymmetric PBI derivatives, which share a
common backbone, but are functionalised with various bay-area substituents.
Density functional theory was combined with a Greens function scattering
approach to compute the electrical conductance of each molecule attached to two
gold electrodes by pyridyl anchor groups. We studied the change in their
conductance in response to the binding of three analytes, namely TNT, BEDT-TTF
and TCNE, and found that the five different responses provided a unique
fingerprint for the discriminating sensing of each analyte. This ability to
sense and discriminate was a direct consequence of the extended {\pi} system of
the PBI backbone, which strongly binds the analytes, combined with the
different charge distribution of the five PBI derivatives, which leads to a
unique electrical response to analyte binding.
