Single Crystal to Single Crystal Transformation of Cu^II Complexes Induced by Dehydrating and Hydrating of Ligands with Chroma Rewritable Behaviors

Abstract

In this work, the single crystal to single crystal (SCSC) transformations in three mononuclear copper complexes [CuL 2 2]Cl2·2H2O (1), [CuL 1 2Cl2] (2), and [CuL 2 2]Cl2·4H2O (3) (L 1 = di-2-pyridyl ketone, L 2 = di(pyridin-2-yl)methanediol) are realized by the irreversible dehydration and hydration reaction of L 1 and L 2 . Dark purple crystal 1 is obtained by self-assembly of L 1 and CuCl2·2H2O in solvothermal reactions, in which the carbonyl group of L 1 undergoes a hydration addition reaction to form L 2 . On heating, 1 transforms to 2 by dehydrating water accompanied by the change of the color and coordination octahedron of CuII ions. In a saturated water vapor environment, 2 can absorb six water molecules and transform to 3 with the same color and coordination environment with 1 but different lattice water. The SCSC process from 2 to 3 is reversible: 3 can transform back to 2 on heating like that of 1. Chroma rewritable behaviors in the structural transformation of the complexes make them visually identifiable temperature or water probes.