Spectrochemistry and artificial color modulation of Cypridina luminescence: indirect evidence for chemiexcitation of a neutral dioxetanone and emission from a neutral amide.

We demonstrate that the emission energy of the cypridinid oxyluciferin depends strongly on the polarity and, to a lesser extent, on the basicity of the medium. The emission color can be tuned by environment effects from violet to green. We also provide firm evidence that the natural system utilizes the neutral form of the emitter.