Preparation and characterization of thermochromic 4,4′-trimethylenedipiperidinium tetrachloronickelate complex and its silica hybrid composite

Abstract

A Ni(II) complex was obtained from the reaction of nickel chloride and 4,4′-trimethylenedipiperidinium chloride (H2TM- DPCl2). Moreover, this thermochromic complex was embedded in silica hybrid material and characterized, as well. The present study is dealing with comparing the thermochromic behavior of this compound including phase transition tem- perature in these two situations. The thermochromic compound was synthesized by mechanochemical method, while, the composite was prepared by sol-gel method at room temperature. They both exhibit a yellow-to-blue color transition under heating. The samples have been subjected to multiple heating/cooling cycles and the dark blue color at elevated tempera- ture fully reverses to the original green-yellow color upon cooling. In order to study the structure and the thermochromic behavior of the complex, Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), scan- ning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermal analysis (TG/DTG/DSC), element analysis, X-ray diffraction (XRD) analysis were performed.