Kinetic study of azobenzene photoisomerization under ambient lighting

Laboratory illumination is sufficiently intense to produce a photostationary state (PSS) of amphiphilic azo-benzene compounds in water. We observed [cis]PSS/[trans]PSS ratios equal to 0.33-1.2 in D2O and 0.37 - 3.8 in dimethyl sulfoxide-d6. ortho-Fluoroazobenzene amphiphiles produced 2-3 times more cis -isomer at equilibrium compared to non-fluorinated compounds which is explained by the isomeric variation in optical absorption profiles. Isomerization kinetics were measured using UV-Vis spectroscopy and the ratio of trans-to -cis over cis-to -trans rates does not quantitatively correlate with the observed PSS. The kinetics define the timescale of ambient photoisomerization where the half-life for PSS formation is 40 min for the fluorinated compounds and 80 min for non-fluorinated compounds.

Automated summary

Laboratory illumination is strong enough to create a photostationary state (PSS) of amphiphilic azo-benzene compounds in water. The [cis]PSS/[trans]PSS ratios were observed to be 0.33-1.2 in D2O and 0.37-3.8 in dimethyl sulfoxide-d6. ortho-Fluoroazobenzene amphiphiles show higher cis-isomer concentration at equilibrium compared to non-fluorinated compounds due to differences in optical absorption profiles. The kinetics of isomerization were measured using UV-Vis spectroscopy and the ratio of trans-to-cis rates does not directly correlate with the observed PSS. The half-life for PSS formation is 40 minutes for fluorinated compounds and 80 minutes for non-fluorinated compounds.