derivatives, N,N'-bis(2-quinolylmethyl)-N,N'-dialkylethylnediamines (alkyl=methyl, ethyl, isopropyl and t-butyl), have been synthesized and their fluorescent responses toward zinc ion were investigated. These compounds exhibit zinc ion-induced fluorescence and their intensities decrease as the alkyl groups become larger. The t-butyl derivative (BQDtBEN) exhibited negligible fluorescence even in the presence