Caged Phosphate and the Slips and Misses in Determination of Quantum Yields for Ultraviolet-A-Induced Photouncaging.

The quantum yields for photouncaging reactions are mostly determined relative to other uncaging reactions, often using 1-(2-nitrophenyl)ethyl-phosphate ("caged phosphate"). Herein, we demonstrate that the quantum yields acquired by using this method can be off by an order of magnitude at the typical irradiation wavelengths around 350 nm and describe an easy-to-use alternative procedure using inexpensive azobenzene.