Molecules responding to external motivation have received considerable attention in recent years that are potentially suitable in the preparation of molecular switches 1 [1]. Generally, a molecular switch is based on a molecule, which can reversibly alter distinct states (on and off) given an external motivation (solvent, temperature, pH, metal ions, light and so on). The sum total of the behavior of complexes is called chromotropism2[2]. In this work we prepared two copper(II) complexes with the general formula of [Cu(L)(H2O)](ClO4)2, 1, and [Cu(L)2](ClO4)2, 2, where L =3-((pyridin-2-ylmethyl)amino)propanamide were synthesized and characterized by elemental analyses, IR, UV-Vis spectroscopy techniques, molar conductance measurements and X-ray crystal analysis (Scheme 1). The chromotropism (halo-, solvato- and ionochromism) of both complexes were studied using visible absorption spectroscopy. The complexes are found to be soluble in water and organic solvents and displayed reversible halochromism due to the flexible and sensitive nature of the amide group with changing pH values. The solvatochromism property is due to structural change followed by solvation of the vacant sites of the complexes. The complexes demonstrated obvious ionochromism and exhibited high-sensitive and selective towards CN- and N3 - anionsin presence of other halide and pseudo-halide ions.
