Photochemical parameters of the studied photochromic systems Z1/F⁻ and Z2/F⁻ measured in DMSO-d₆ solution (T = 298.15 K)^a.

Photochromic system	Azo–hydrazo PSS (% azo)	Hydrazo–azo PSS (% azo)	Φ A–H (%)	Φ H–A (%)
Z1/F−	98	49	9.5 ± 0.5	0.19 ± 0.04
Z2/F−	96	30	23.6 ± 1.1	0.11 ± 0.02

^a Φ _A–H – photochemical quantum yield of blue azo form transformation to yellow hydrazone form; Φ_H–A – photochemical quantum yield of yellow hydrazone form transformation to blue azo form.