A Categorical Naked-Eye Detection of Cu2+ and Zn2+ through a Donor-Acceptor-Donor (D-A-D)-Type Salicylaldimine: An Experimental and Theoretical Approach

Abstract

A Schiff base viz., 2,3-bis-(3, 5-di-tert-butyl-2-hydroxybenzylidene) amino maleonitrile (TBCN), having donor–acceptor–donor (D–A–D) type constitution exhibited Cu2+ and Zn2+ guided specific modulations in its ICT (intramolecular charge transfer) characteristics. The corresponding naked eye changes for Cu2+ and Zn2+ involved the shifting of characteristic ICT band of TBCN at ∼472 nm (yellow) to ∼ 566 nm (pink) and ∼590 nm (indigo blue) respectively in a semi-aqueous medium (EtOH:H2O in a ratio of 8:2 v/v). The TBCN as well as its ensembles with Cu2+ and Zn2+ were fully characterized through their single crystal XRD studies along with spectroscopic and mass spectral studies. The DFT and the time-dependent DFT calculations provided a genuine rationale for separate naked eye colorimetric changes of TBCN for Cu2+ and Zn2+. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim