Synthesis and Photochromism of Spirobenzopyrans and Spirobenzothiapyran Derivatives Bearing Monoazathiacrown Ethers and Noncyclic Analogues in the Presence of Metal Ions

Abstract

Spirobenzopyrans bearing monoazathiacrown ethers and noncyclic analogues were synthesized, and their ion-responsive photochromism depending on the dual metal ion interaction with the crown ether and the phenolate anion moieties was examined using alkali and alkaline-earth metal ions, Ag(+), Tl(+), Pb(2+), Hg(2+), and Zn(2+). The prepared spirobenzopyrans showed a selective binding ability to Mg(2+) and Ag(+) with negative and positive photochromism, respectively. Among the metal ions, only Ag(+) facilitated photoisomerization to the corresponding merocyanine form. Depending on the ring size of the monoazathiacrown ether moieties, soft metal ions such as Hg(2+) and Ag(+) showed significant shifts in the UV-vis absorption spectra, while hard metal ions such as Mg(2+), Zn(2+), and Pb(2+) did not afford any meaningful shift. This result reflects that the monoazathiacrown ether and phenolate anion moieties prefer soft and hard metal ions, respectively. Therefore, the Mg(2+) and Ag(+) selectivities are mainly derived from the phenolate anion and monoazathiacrown ether moieties, respectively. On the other hand, a spirobenzothiapyran bearing 3,9-dithia-6-monoazaundecane showed a remarkable selectivity to Ag(+).

Temperature‐Controlled Switchable Photochromism in Solid Materials

“…Recently, the development of spiropyran and spirooxazine systems that can reversibly switch between positive and negative photochromism has raised much interest as they can be used to generate frequency‐dependent photoinduced optical effects exploitable for controlling input/output optical signals in logic gates, information recording/processing, and rewritable printing devices . To date, most of the reported examples showing switchable photochromism were developed as proof‐of‐concept liquid solutions where chemicals had to be sequentially added to alter the relative stability of the SP and MC isomers: acids, or metal ions– to stabilize the colored form as MCH + or metal–MC complexes and bases to compete with coordinating ligands or complexing metals to reestablish the non‐colored SP isomer.…”

Analytical and Separation Chemistry by Taking Advantage of Organic Photochromism Combined with Macrocyclic Chemistry

“…9 In spirobenzopyran derivatives incorporating a monoazatrithia-12-crown-4 moiety, an analog of 1, where the monoaza-12-crown-4 moiety was replaced with a monoazathiacrown ether moiety, the photochromism reflected the metal-ion complexing property of their thiacrown ether moiety. 10 Each of the thiacrowned spirobenzopyrans forms complexes of Mg 2+ and Ag + with negative and positive photochromism, respectively. Silver ion, which has a high affinity to the thiacrown moiety, facilitated photoisomerization to their corresponding merocyanine form, but the phenolate anion did not interact with a Ag + in the thiacrown ether moiety.…”

Solid Materials with Tunable Reverse Photochromism

“…4,5 Normally, these compounds show direct photochromism since their thermodinamically stable form is the closed, colourless spiro state, which isomerizes to the coloured, unstable merocyanine (MC) when irradiated. 1,3 However, several methodologies have been proposed to alter the relative stability of both isomers and attain reverse photochromism, [6][7][8][9][10][11][12][13][14][15][16][17] where stabilization of the MC form is accomplished via: a) chemical modification of the dyes [22][23][24][25][26] resulting in a dramatic variation of their electronic properties, 27 intramolecular hydrogen-bond formation, 23 or complexation with metals; [28][29][30][31][32][33][34][35][36] b) dispersion of the dyes in selected media, [37][38][39][40] which either stabilize the more polar zwitterionic MC structure (e.g. via hydrogen-bond interactions) or convert it into the protonated form MCH + through acid-base reactions.…”