Theoretical study of the effect of resonance on π–π stacked firefly oxyluciferin dimers

Firefly oxyluciferin is a prime example in which π–π stacking interactions play an important role, by being the basis for the formation of sandwich-like oxyluciferin complexes. In the present study, we have used a theoretical methodology to further understand the effect of π–π stacking interactions in the properties of oxyluciferin molecule. More specifically, we have analysed the effect of resonance changes in oxyluciferin π–π stacking dimers. We have found that resonance changes have little effect on the ground state properties of the dimmers. More interestingly, by modulating the resonance of the dimmers we can obtain different transition energies and efficiencies. This results in changes in the degree of contributions made by the different orbital excitations that compose the excitation transition.