Machine Learning Analysis for Photo-Induced Phenomena of 1-Methyl-3-(N-(1,8- Naphthalimidyl)ethyl)imidazolium Salts

Abstract

1-Methyl-3-(N-(1,8-naphthalimidyl)ethyl)imidazolium (MNEI) salts show various photochemical phenomena depending on the guest anion. We used machine learning techniques to extract decisive factors that dominate the fate of MNEI salts after UV irradiation and prepared a decision tree diagram to deduce their photochemical phenomena before experiments.

Unique Photophysical Properties of 1,8-Naphthalimide Derivatives: Generation of Semi-stable Radical Anion Species by Photo-Induced Electron Transfer from a Carboxy Group

“…In TENDI, although the maximum fluorescence intensities were approximately one-tenth of those observed for TENI, the monomer fluorescence emission peak was detectable at around 410 nm. 21 Therefore, the photo-induced colorimetric reactions of TENI, CH 3 O-TENI, NO 2 -TENI, and TENDI in the presence of sodium succinate were investigated (Figure 4). In TENI, the solution turned yellow under UV light irradiation and the appearance and decrease of absorbance peaks were observed at around 430 nm and at around 345 nm, respectively.…”

“…In our previous work, the importance of aggregation to the photoinduced colorimetric reaction was suggested. 20,21 PEGNI is an amphiphilic molecule, and thus, hydrophobic NI groups should be aggregated in water as micelles. Thus, we conjecture that aggregation of the NI groups contributes to the generation and/or stabilization of the radical anion in the PEGNI system.…”

“…The colorimetric reaction of MNEI proceeded especially readily in the presence of molecules having multiple carboxy groups, such as succinate, citrate, and polyacrylate, or amphiphilic carboxylate derivatives such as laurate and phenylacetate. 20,21 In contrast, the yellowing reaction was not observed in the presence of the same amount of acetate, but it was slightly observed in the presence of a ca. 30-fold higher amount of acetate.…”

“…18,19 In addition, MNEI underwent a photo-induced colorimetric reaction, in which the MNEI aqueous solution became yellow in the presence of carboxylate derivatives by UV light irradiation. 20,21 The yellow chemical species was unstable to O 2 , and the yellow color gradually disappeared under an ambient condition. The colorimetric reaction of MNEI proceeded especially readily in the presence of molecules having multiple carboxy groups, such as succinate, citrate, and polyacrylate, or amphiphilic carboxylate derivatives such as laurate and phenylacetate.…”

“…In addition, we used machine learning analysis to extract decisive factors that dominate the fate of MNEI salts after UV light irradiation, and the results suggested that pK a , the number of carboxy groups, and the bulkiness of carboxylate derivatives were important factors for the colorimetric reaction. 21 However, the mechanism for the photo-induced colorimetric reaction has not been clarified. If the mechanism by which the carboxy groups are selectively detected could be revealed, it would provide a novel design principle for anion sensor molecules.…”