Synthesis of Novel Iono- and Photochromic Spiropyrans Derived from 6,7-Dihydroxy-8-Formyl-4-Methyl-2H-Chromene-2-One

Figure 3

(a) ¹H NMR spectra of (4a) in dark conditions in CD₃CN-nitrobenzene-𝑑₆ (1∶1 v/v) and (b) in presence of Mg(ClO₄)₂⋅3H₂O after 10 minutes; (c) 1 hour (𝜈_Mg²⁺/𝜈_(4a)=5).

(a)

(b)

(c)