1, 4-Bis [2-aminoethylamino] anthracene-9, 10-diones selectively bind with Cu2+ to form complexes with unusual selectivity under basic conditions. The deprotonation of the aryl amine NH in the case of these chemosensors causes a bathochromic shift in the absorption band from 585nm and 635nm to 725nm and enables ratiometric estimation of Cu2+ between pH 8 and 12.
[Krapcho, A. Paul; Getahun, Zelleka; Avery, Kenneth L.; Vargas, Kevin J.; Hacker, Miles P.; et al. Journal of Medicinal Chemistry, 1991 , vol. 34, # 8 p. 2373 - 2380]