Photoinduced pH drops in water

Abstract

A 2-hydroxyazobenzene platform has been evaluated to photorelease protons in aqueous solutions. Three different systems relying on molecular, supramolecular and polymeric strategies have been investigated in order to tune the water solubility and the thermodynamic and kinetic properties. This paper first reports on the syntheses and the physico chemical analyses for each system. Subsequently, we show that the three strategies are appropriate to reversibly photo-generate tunable pH drops in water up to one pH unit amplitude and at the 10-100 s timescale, upon transient illumination at 365 nm.

Substituent effects on absorption spectra of pH indicators: An experimental and computational study of sulfonphthaleine dyes

“…These values are compared to calculated vertical absorption energies E vert . The molecules of the test set ( Figure 1) can be divided into three types: those with electron donating substituents (2-5); with electron withdrawing substituents (6,7) and those with both electron donating and withdrawing groups (8)(9)(10). The UV/Vis spectra of dyes 2 and 6 are included in Figure 3 as examples of dyes with electron donating and electron withdrawing substituents, respectively.…”

“…[3] The most exploited chromic types are thermochromism and photochromism, [4,5] but halochromism (pH sensitivity) is also increasingly studied and put into practice. [6][7][8][9][10][11][12] Our main interest lies in the possible application of halochromic dyes in pH-responsive polymers, or more precisely intelligent textiles. This is part of a larger research field, namely functionalized polymers.…”

Photoresponsive Ion Extraction/Release Systems: Dynamic Ion Optodes for Calcium and Sodium Based on Photochromic Spiropyran

“…20,21 For other ionic species photoactive chelating compounds were used for reversible 22−25 and irreversible affinity changes (photo cages). 26 In our work, however, the driving force for triggered ion exchange is the change in p K a of a photoactive chromoionophore.…”

Towards More Effective, Reversible pH Control by Visible Light Alone: A Thioindigo Photoswitch Undergoing a Strong pKa Modulation by Isomer‐Specific Hydrogen Bonding

“…Exploratory computational geometry optimizations of mono‐anionic 1 (Scheme b) indicate that in the cis isomer the phenolic residues readily adopt an O−O distance in the order of 2.3 Å, i. e. a typical value for very short and strong hydrogen bonds, such as in (FHF) − without signs of distortion in the molecular backbone. Thus, the scene is set for an efficient hydrogen bond induced acidity modulation,,, whose operation region can be tailored in a broad range including neutrality by modification of the substituents X.…”