2‐Hydroxyazobenzenes to Tailor pH Pulses and Oscillations with Light

Abstract

This paper evaluates the 2-hydroxyazobenzene platform for tailoring proton concentration pulses and oscillations with monochromatic light. The easily prepared 2-hydroxyazobenzenes exhibit large absorptions in the near-UV range. Photoisomerization was investigated by UV/Vis absorption, (1)H NMR spectroscopy, and steady-state fluorescence emission. In the whole investigated series, the trans stereoisomer of the 2-hydroxyazobenzene motif provides the corresponding cis derivative with an action cross section in the 10(3) M(-1) cm(-1) range. At the same time, photoisomerization is accompanied by a significant pK drop of the phenol group. According to the phenyl-substituent pattern, cis-to-trans thermal back-isomerization can be tuned in the 10 ms-100 s range. Up to 2 units of reversible pH drops or pH oscillations on the 10 s timescale have been obtained by appropriately tailoring single-wavelength illumination of 2-hydroxyazobenzene solutions.

Identification of two-step chemical mechanisms and determination of thermokinetic parameters using frequency responses to small temperature oscillations

“…[31][32][33] First, we chose to reveal dynamics using a periodic forcing. Actually, relaxation techniques have been implemented in the frequency-domain for long, 17, 24 the analysis of transfer functions providing values of characteristic times, 8,[34][35][36][37][38][39][40][41] or even giving indication on the followed mechanisms. 36,38,39 With light modulation, one could learn on both photophysical [34][35][36] and photochemical 37-39 phenomena.…”

Systematic Modulation of Hydrogen Bond Donors in Aminoazobenzene Derivatives Provides Further Evidence for the Concerted Inversion Photoisomerization Pathway

“…By introducing a redox active metal ion such as iron or cobalt coordinated onto an AB-functionalized ligand, metal oxidation state changes shift the AB absorption maximum (λ max ), which causes both isomers to absorb strongly at the same wavelength. [27,28] Alternately, an AB functionality may be incorporated into a metal binding ligand motif such as a crown ether [29,30] or a catechol. Formation of ion pairs between AB carboxylates and bulky quaternary ammonium salts block photoisomerization through steric interactions.…”

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.…”