Solving secular equations for molecular motors within the Hückel approximation using Python

Hückel theory is an empirical quantum chemical method that allows students to solve the secular equations using pen-and-paper. Usually simple hydrocarbons are considered for this exercise, which might not be that inspiring to students. In this work, we present basic Python code to solve this eigenvalue problem and apply it successfully to molecular motors. It is demonstrated that Hückel theory can qualitatively predict the red-shifting of the excitation wavelength upon substituting the aromatic core of a molecular motor. The Hückel calculated frontier molecular orbitals agree well with density functional theory.