  The {\pi}-{\pi} interactions between organic molecules are among the most
important parameters for optimizing the transport and optical properties of
organic transistors, light-emitting diodes, and (bio-) molecular devices.
Despite substantial theoretical progress, direct experimental measurement of
the {\pi}-{\pi} electronic coupling energy parameter t has remained an old
challenge due to molecular structural variability and the large number of
parameters that affect the charge transport. Here, we propose a study of
{\pi}-{\pi} interactions from electrochemical and current measurements on a
large array of ferrocene-thiolated gold nanocrystals. We confirm the
theoretical prediction that t can be assessed from a statistical analysis of
current histograms. The extracted value of t ca. 35 meV is in the expected
range based on our density functional theory analysis. Furthermore, the t
distribution is not necessarily Gaussian and could be used as an ultrasensitive
technique to assess intermolecular distance fluctuation at the subangstr\"om
level. The present work establishes a direct bridge between quantum chemistry,
electrochemistry, organic electronics, and mesoscopic physics, all of which
were used to discuss results and perspectives in a quantitative manner.

Mesoscale and Nanoscale Physics