Study of the Zn II Complexes of 1,1′‐Binaphthyl‐Based Schiff Bases: Fluorescent Detection of Thiocyanate

Two diastereomeric Schiff bases ( Sa,R )‐ 2 and ( Sa,S )‐ 2 are prepared from the condensation of ( S )‐3,3′‐diformyl‐1,1′‐bi‐2‐naphthol with d ‐ and l ‐2‐phenylglycinol. Upon coordination with Zn 2+ , ( Sa,R )‐ 2 shows much greater fluorescence than ( Sa,S )‐ 2 does. The effect of various anions on the fluorescence of these Zn 2+ complexes is studied. It is found that ( Sa,S )‐ 2 exhibits large fluorescence enhancement in the presence of thiocyanate but not with other anions. This compound can be used as a sensitive as well as selective fluorescent probe for thiocyanate that is of significant environment and health importance. Spectroscopic studies have revealed interesting dimeric [2+3] structures of these complexes.