Abstract—The spectroscopy and photochemistry of brilliant green leucocyanide1awere investigated at room and low temperature, in polar and nonpolar solvents. At 77 K,1aexhibits solvent independent absorption, fluorescence (φf= 0.1), and phosphorescence (φp= 0.5). Solvent effects become important at room temperature; in polar solvents, φf, decreases and photodissociation yielding brilliant green dye 3 occurs [φdis,(EtOH) ˜0.91. Dye formation and1afluorescence can be quenched by 0.1Mcrotononitrile. Attempts to sensitize dye formation with triplet sensitizers were unsuccessful. The spectroscopy of 3 was also ex