Structure and Chromotropic Properties of 2-Picolylamine-Ni(II) Complex

A symmetric complex [NiL2(H2O)2]Cl2, where L = 2-picolylamine was synthesized and characterized by spectroscopic and structural methods. Single crystal X-ray studies reveal that the Ni(II) center located in a pseudo-octahedral N4O2 environment with bidentate ligands L positioned in basal and two water molecules in the apical position. The complex is solvatochromic, ionochromic and thermochromic. The observed positive solvatochromism in polar solvents is due to the substitution of water molecules by the solvent. The complex demonstrated distinct ionochromism towards cyanide and bromide anions in the presence of other halides and pseudo-halide anions and can be served as a ‘‘naked-eye’’ indicator for the qualitative detection of these anions. The compound showed reversible thermochromism in solid-state from blue to green due to dehydration and hydration process.