Understanding the excited state decay mechanism of complex systems: a general first-order kinetic model

In this work, we have proposed and evaluated a first-order kinetic model to describe the excited-states dynamics of molecules as a computationally cheaper alternative to describe and understand the photophysical profile of large systems. The method is based on calculating the radiative and nonradiative rate constants of all photophysical processes of a collection of crucial low-lying excited states and modeling the decay over time using a first-order kinetic model. We have successfully applied the method to the [Ru(bpz)₃]²⁺ (bpz = 2,2'-bipyrazyl) complex as a case study, obtaining good results. By employing this first-order kinetic model, it is possible to simulate the time-dependent decay process and the evolution of the excited-state population, revealing not only the primary deactivation pathway but also secondary states that contribute to the overall decay mechanism, highlighting alternative channels that may lead to photochemical side products. This approach provides a computationally efficient yet accurate method for studying more intricate systems relevant to photoinduced processes. It enhances the understanding of these compounds and offers guidance for fine-tuning their chemical and structural properties for targeted applications.