Materials and Nanomaterials with Stimuli-Responsive Behaviour based on the Flexibility of the Copper-Halide Chain

Abstract

The present PhD Thesis has been realized in the Inorganic Chemistry Department of the Autonomous University of Madrid (Universidad Autónoma de Madrid), under the supervision of Dr. Félix Zamora Abanades and Dr. Pilar Amo Ochoa of the Nanomaterials Research Group. To achieve the completion of this thesis, a series of materials based on coordination polymers (CPs) has been designed, synthesized and characterized. These compounds present electrical and luminescent properties which can be tuned by the presence of physical or chemical stimuli. These materials are commonly known to possess a dynamic or stimuli-responsive behavior. Apart from the experiments conducted in the presence of several stimuli, theoretical calculations have been used when necessary in order to rationalize the observed behaviors. This thesis will be divided into six chapters: an introduction to CPs and stimuli-responsive materials, accompanied by the purposes of the thesis (Chapter 1); three chapters where the results of the thesis and the subsequent discussion are detailed (Chapters 2-4); the conclusions (Chapter 5) and, finally, the experimental section (Chapter 6). The compounds described in chapter 2 share a common building block: copper(I) iodide and functionalized nitrogen-donor ligands. Aiming to obtain new materials based on one- and two-dimensional CPs with double zigzag Cu-I chains, this metal salt has been combined with the following organic ligands: methyl isonicotinate (MeIN), methyl 2-aminoisonicotinate (NH2-MeIN), aminopyrazine (Apyz) and 3-chloroisonicotinic acid (Cl-HIN). The obtained compounds have been characterized by means of infrared spectroscopy (IR), elemental analysis, single crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD), and their electrical and luminescent properties have been evaluated. Afterwards, they have been prepared as nanostructures. Similarly, we have been able to obtain nanostructures of three previously described CPs, obtained by combining copper(I) iodide and isonicotinic acid (HIN), ethyl isonicotinate (EtIN) or 2-amino-5-nitropyridine (ANP). In chapter 3, a new compound based on a double Cu-I chain, where the terminal ligand is 3,5-dichloropyridine (Cl2-py), is described. This compound presents itself in two different forms depending on the synthetic method followed to achieve its preparation. In this chapter, the difference in the luminescent properties showed by the two forms of this compound will be explained, and it will be proven that these differences are caused by the presence of defects in one of them. Chapter 4 discloses the preparation of new composite materials based on two of the already outlined CPs and flexible organic matrices such as polyvinylidene difluoride (PVDF) and polylactic acid (PLA). The homogeneity and the luminescent and mechanical properties of these new materials will be studied, in order to present them as candidates for industrial or daily-life applications.