Fig. 2: Characterization of the cycloaddition product. | Nature Communications

Fig. 2: Characterization of the cycloaddition product.

From: Green light triggered [2+2] cycloaddition of halochromic styrylquinoxaline—controlling photoreactivity by pH

Fig. 2

a UV/vis spectra of PEG-SQ and (PEG-SQ)2 dimer after irradiation at 510 nm with 9.29 × 1022 photons in water (10 mg mL−1), with the gray bars showing the appearance of new absorption peaks specific to quinoxaline due to the change in conjugation after irradiation at 510 nm. The insert shows the expanded absorbance spectra between 450 and 550 nm. b SEC data (calibrated against PMMA) of PEG-SQ and (PEG-SQ)2 after irradiation at 510 nm with 9.29 × 1022 photons in water (10 mg mL−1). c SEC-MS analysis of cycloaddition of PEG-SQ after irradiation at 510 nm with 9.29 × 1022 photons. SEC trace of the (PEG-SQ)2 peak at 16.3 min jointly with the PEG-SQ peak at 17.7 min. High resolution MS spectrum displaying doubly charged species of the (PEG-SQ)2 peak after 16.3 min of elution in the SEC trace. The m/z difference between patterns is 22.013, corresponding to half of one PEG repeating unit. Zoom into the MS spectra of experimental and simulated isotopic patterns, indicating their excellent agreement. The inset table shows the theoretical and experimental m/z values of the (PEG-SQ)2 dimer.

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