A DFT exploration of structural and electronic properties of a photoswitchable octapeptide cyclized with (4-aminomethyl)phenylazobenzoic acid

► Observing changes during optimization steps show the necessity of diffuse functions. ► Optimized structures show different types of intramolecular H bondings. ► H bondings are confirmed by NBO, NMR and NQR parameters. ► NBO analysis can answer some observed discrepancies on NMR and NQR calculations. ► Analyzing theoretical and experimental 1H CS confirms the predicted H bondings.