Fig. 4: Photoswitching of vanadate aggregation.

⁵¹V-NMR spectra of the two photostationary states of a vanadate/ligand solution (1.5 mM Na₃VO₄, 100 mM CHES buffer, 50 mM NaOH, pH 9.53, I = 150 mM, 0.75 mM receptor) upon irradiation a with 365 nm and b 440 nm. The structural schemes (for explanation see Fig. 5) represent the vanadate/ligand species that contribute to the corresponding ⁵¹V NMR signals above, and the bars indicate the relative concentrations. The incomplete photochemical conversion of the ligand from the trans to the cis isomer (70%) accounts for the 17% tetravanadate in solution (a). Upon heating to 70 °C for 30 min conversion is complete and the tetravanadate signal is reduced below the detection limit (Supplementary Fig. 5)