Mt. Stauffer et Sg. Weber, Optical control of divalent metal ion binding to a photochromic catechol: Photoreversal of tightly bound Zn2+, ANALYT CHEM, 71(6), 1999, pp. 1146-1151
Photochromic molecules with functional groups that bind metal ions strongly
make possible the development of photoreversible sensors and preconcentrat
ors for detection of metal ions at trace concentrations. While several phot
ochromic metal chelators have been reported, none have been shown to bind s
trongly to divalent metal ions. A novel photochromic benzopyran 2, which is
a photochromic catechol, binds Zn2+ strongly and reversibly. The thermal e
quilibrium between open and closed 2 is slow. Thus, binding of Zn2+ to 2 is
slow in the dark. Under illumination with 306-416-nm light, Zn2+ binds rap
idly to open 2. The stable complex dissociates upon illumination with visib
le light, showing that both formation and dissociation of the complex are c
ontrollable with light. A binding constant of 1.1 x 10(9) is estimated from
a Job plot, which also indicates formation of a 1:1 Zn2+/open 2 complex.