Deciphering Hidden Charge Transport Pathways in Break-Junction Conductance Histograms of Tripyridyl-Triazine...

Break junction (BJ) techniques and computational methods have jointly unraveled the fundamental principles that govern charge transport in molecular systems. However, recent experiments on junctions with multiple electronic pathways have challenged the computational deconvolution of BJ data in terms of individual circuit contributions. Here, we investigate charge transport in a 2,4,6-tris(2',2″,2‴-pyridyl)-1,3,5-triazine (o-TPTZ) molecular junction using a recently developed computational framework that directly simulates conductance histograms while accounting for conformational diversity, steric factors, and combinations of multiple embedded molecular circuits. We show that a weighted sum of contributions from single- and multi-terminal circuits best rationalizes the existing BJ data for o-TPTZ and that its conductance can be expressed in terms of three types of irreducible "basis" circuits. Further, we predict conductance histograms of structurally related isomers m-TPTZ and p-TPTZ. Our analysis reveals that changing the relative positions of the pyridyl nitrogen atoms of peripheral rings in TPTZ modifies both electrode accessibility and quantum interference between transport pathways to tune the conductance of the basis circuits and produce distinct signatures in the resulting conductance histograms. Finally, we examine the contribution of multi-orbital quantum interference effects to the basis circuit conductance that produce distinct conductance features in the three molecular junctions.