Aiming at an accurate prediction of vibrational and electronic spectra for medium-to-large molecules: An overview

In this tutorial review, we present some effective methodologies available for the simulation of vibrational and vibrationally resolved electronic spectra of medium‐to‐large molecules. They have been integrated into a unified platform and extended to support a wide range of spectroscopies. The resulting tool is particularly useful in assisting the extensive characterization of molecules, often achieved by combining multiple types of measurements. A correct assessment of the reliability of theoretical calculations is a necessary prelude to the interpretation of their results. For this reason, the key concepts of the underlying theories will be first presented and then illustrated through the study of thiophene and its smallest oligomer, bithiophene. While doing so, a complete computational protocol will be detailed, with emphasis on the strengths and potential shortcomings of the models employed here. Guidelines are also provided for performing similar studies on different molecular systems, with comments on the more common pitfalls and ways to overcome them. Finally, extensions to other cases, like chiral spectroscopies or mixtures, are also discussed. Cost‐effective methodologies to simulate and interpret accurate vibrational and electronic spectra, directly comparable to experiment, are described from a theoretical and practical perspectives. Key aspects regarding their application on real cases are discussed through the design of a complete computational protocol starting from the definition of the best suited electronic structure calculation method, using thiophene and bithiophene as test cases. Possible shortcomings and strategies to overcome the limitations of those methods are also presented.