A diamide–diamine based Cu2+ chromogenic sensor for highly selective visual and spectrophotometric detection

A diamide–diamine based sensor 3 possessing anthracene-9,10-dione as a chromogenic moiety has been synthesized and demonstrates a highly selective colour change from red to blue with Cu2+ for visual detection of Cu2+ (5–50 μM). Other metal ions, viz. Fe2+, Cr3+, Co2+, Ni2+, Zn2+, Cd2+, Ag+, Pb2+, Na+, K+, Mg2+, Ca2+, Sr2+ and Ba2+ cations do not lead to any change in colour and their presence does not interfere with the visual and quantitative analysis of Cu2+. The selective deprotonation of an aryl amine NH by Cu2+ is responsible for a bathochromic shift and significant colour changes. Significantly, the stability of the 3·Cu2+ complex between pH 7 and 12 allows Cu2+ estimation under neutral and basic conditions.