The Effect of Tb and Sm Ions on the Photochromic Behavior of Two Spiropyrans of Benzoxazine Series in Solution

Table 2

The experimental values of absorption, M(III)-SP formation rate constant (𝑘₂), thermal ring closure rate constant (𝑘₋₂), equilibrium (𝐾_𝑒) constant of the reversible reaction, relaxation time τ_{M(III)-open-SP}, and colorability in DMF at 295 ± 1 K. Error limits of the kinetics parameters are in the order of about 5%.

Complexes	λopen-M(III) (nm)	𝑘−2×10^3 (min^−1)	𝑘2×10^3 (min^−1)	τM(III)-open-SP (min)	𝐾𝑒	Colorability M^−1cm^−110^−2
Tb(III)-SP(I)	412	4.04	661	247	163	7.02
Sm(III)-SP(I)	414	4.55	258	219	56	7.85
Tb(III)-SP(II)	412	8.16	327	122	40	7.73
Sm(III)-SP(II)	414	4.77	225	209	47	7.72