N-[4-[(1E)-2-(4-Aminophenyl)diazenyl]phenyl]-2,5-dihydro-2,5-dioxo-1H-pyrrole-1-acetamide is an intermediate in synthesizing 2-[[4-[(1E)-2-[4-[[2-(2,5-Dihydro-2,5-dioxo-1H-pyrrol-1-yl)acetyl]amino]phenyl]diazenyl]phenyl]amino]-N,N,N-triethyl-2-oxoethanaminium Chloride (D450375). It is a light-activated gated ion channel for remote control of neuronal firing.