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

Figure 2

Absorption spectra of (4a) in dark conditions in acetonitrile solution before (1) and after addition of Mg(ClO₄)₂ (2); after 5 minutes (3); 10 minutes (4); 20 minutes (5); 30 minutes (6); 45 minutes (7); 60 minutes (8); 90 minutes (9); 120 minutes (10), 180 minutes (11) ([4a]=2.5×10⁻⁵ M, [Mg²⁺]=5×10⁻⁴ M).