Fig. 3. (a) UV-Vis spectra of o-A¹₂L₃Zn₂ during ring-closing and (b) c-A¹₂L₃Zn₂ during the ring-opening process (CH₃CN/CHCl₃, v : v = 1 : 1, 1 × 10⁻⁵ mol L⁻¹, 298 K). (c) Cycled signals for absorbance at 627 nm during alternate ring-closing/opening processes (left), and color change photos (right). (d) Time-dependent ¹H NMR spectral evolution of o-A¹₂L₃Zn₂ under UV irradiation (400 MHz, CD₃CN, 298 K).