Synthesis and performance study of nonionic photoacid generators based on Norbornene-imide

Six N-hydroxy-5-norbornene-2,3-dicarbonylimine sulfonates(3a-3f) were created in this paper and produced as non-ionic photoacid generators (PAGs) in good yields. 1H NMR and 13C NMR were used to confirm the structures of the compounds and 19F NMR was used to further justify the structure of 3a. Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) showed that all six PAGs have good thermal stability. Additionally, the solvent's influence on PAG compounds was examined using Ultraviolet and visible spectrum (UV-vis) and 254 nm fluorescence spectra (FS). The changes in the six PAG components of the products were monitored by HPLC on exposure to UV light (254 nm). An exposure acid production assay based on the spectrophotometric approach was developed using Rhodamine B (RB) as the acid sensor. The degradation and acid production quantum yields of the six PAGs were tested, and the results showed that all PAGs exhibited a high acid-producing capacity. In addition, we present a potential mechanism for the photogeneration of sulfonic acid, and DFT time calculations using Gaussian calculations support the N-O bond cleavage mechanism of PAG 3c.