Photochromic Property of Anionic Spiropyran with Sulfonate-substituted Indoline Moiety

Abstract

For fabricating photoresponsive multifunctional materials, we have developed the potassium salt of a new anionic spiropyran, 1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indoline]-5′-sulfonate (1−), with the sulfonate group present on the indoline moiety and whose crystal structure was revealed by single-crystal X-ray diffraction analysis. The photochromism of 1·K was demonstrated at room temperature in the KBr-diluted state, as well as in solution. The protonated spiropyran 1H shows negative photochromism.

The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome

“…At the same time, Zhou and co-workers assigned an intermediate observed upon protonation of 6 0 ,8 0 -dinitrospiropyran to a protonated form with a broken C spiro -O bond that had not yet achieved planarisation (''species X''). 87 The proposed intermediacy of the protonated cisoid form was supported by Shiozaki shortly thereafter, 88 who showed a better-defined response to protonation of spiropyran in ethanol with sulfuric acid than with the more commonly used trifluoroacetic 68,69,[89][90][91][92][93][94][95][96][97] and hydrochloric acids. 18,[98][99][100][101][102][103][104][105][106][107][108][109] These observations indicate that distinct protonated cisoid and transoid structures differ in pK a .…”

Direct Access by Mechanochemistry or Sonochemistry to Protonated Merocyanines: Components of a Four‐State Molecular Switch

“…[18] Formation of salts with the protonated form (i.e., MEH + )i si nducedint he presence of acids. [19,20] At hree-state molecular switch based on SP_NO 2 has been designed and investigated. [21] It combines light and chemical stimuli that transduce into optical outputs through as equence of logic operations involving the SP,M E, and MEH + forms ( Figure 1).…”

Water‐Soluble Spiropyrans with Inverse Photochromism and Their Photoresponsive Electrostatic Self‐Assembly

“…The ring-opening causesc hargeaseparation,whichi nduces al arge dipolem omenti nM C. At the same time, this process is accompanied by as ubstantial structural change, which is not only spatial but also electronic in nature. [51][52][53][54] In the latter case, the sulfonate group is almosta lwaysi ntroduced by alkylation of the indoline nitrogen via as ultone. Furthermore, this increases the basicity of the MC isomer in comparison to SP and makes it pronet op rotona-tion.…”

“…Furthermore, this increases the basicity of the MC isomer in comparison to SP and makes it pronet op rotona-tion. [53] With the goal of using spiropyrans for self-assembly in aqueous solution, in this study,w es ynthesized four new spiropyrans with 2-3 sulfonate groupsdistributed among both aromatic cores (Scheme 2). [38][39][40] Particularly for biological applications, water solubility of spiropyransi sn ecessary.S ince the majority of spiropyrans are poorly water-soluble, they have mainly been studied in nonaqueous solvents and relativelylittle is knownoft heir behavior in water.T he few that are water-soluble incorporateo nly asingle ionic group such as acarboxylate, [41][42][43][44][45] aquaternary nitrogen group, [46][47][48][49][50] or as ulfonate group.…”