biostudies-literatureUnknown12(42)Hricovini MHigh-resolution NMR experiments revealed that differently substituted quinazolinone-based Schiff bases undergo <i>anti</i> to <i>syn</i> isomerisation on exposure to ultraviolet light in DMSO solution. The degree <i>anti</i> to <i>syn</i> conversion varied significantly upon substitution (between 5% and 100%) and also showed two noteworthy features: that relaxation back to the <i>anti</i>-form goes far faster (by at least 3 orders of magnitude) when the C₆ rings B and C have <i>ortho</i>-OH substituents, and that relaxation can also be significantly sped up by addition of acid. Two possible mechanisms explaining the differences in relaxation process have been proposed: (I) the interaction of the azomethine hydrogen with the carbonyl oxygen results in slower reversion to the <i>aRSC advances27442-27452https://www.ebi.ac.uk/biostudies/studies/S-EPMC9524441biostudies-literatureA study of the photochemical behaviour and relaxation mechanisms of <i>anti</i>-<i>syn</i> isomerisation around quinazolinone -N-N[double bond, length as m-dash] bonds.PMC9524441Hricovini MAsher JRfalseA study of the photochemical behaviour and relaxation mechanisms of <i>anti</i>-<i>syn</i> isomerisation around quinazolinone -N-N[double bond, length as m-dash] bonds.High-resolution NMR experiments revealed that differently substituted quinazolinone-based Schiff bases undergo <i>anti</i> to <i>syn</i> isomerisation on exposure to ultraviolet light in DMSO solution. The degree <i>anti</i> to <i>syn</i> conversion varied significantly upon substitution (between 5% and 100%) and also showed two noteworthy features: that relaxation back to the <i>anti</i>-form goes far faster (by at least 3 orders of magnitude) when the C₆ rings B and C have <i>ortho</i>-OH substituents, and that relaxation can also be significantly sped up by addition of acid. Two possible mechanisms explaining the differences in relaxation process have been proposed: (I) the interaction of the azomethine hydrogen with the carbonyl oxygen results in slower reversion to the <i>a2022-01-01T00:00:00Z2022 Sep2025-04-05T13:27:38.748Z2025-04-05T13:27:38.748ZS-EPMC95244413632116210.1039/d2ra04529j