Coexistence of mechanochromic and selective vapochromic behaviors in a discrete trinuclear NiII complex

Details

Supervisors

Garcia, Yann

Faculty

Faculté des sciences

Degree label

Master [120] en sciences chimiques, à finalité spécialisée: chimie de l'industrie

Abstract

The CMOL group is a research department within the Institute of Condensed Matter and Nanosciences (ICMN) at the Université catholique de Louvain, overseen by Professor Yann Garcia. The laboratory mainly focuses on the development and study of new hybrid molecular-based magnetic materials, including spin crossover (SCO), photothermal, and piezochromic materials, as well as exploring their applications in various fields. One of the research hotspots at the laboratory is the development and study of chromic materials that can respond to multiple external stimuli. The aim of this thesis is to study the coexistence of mechanochromic and selective vapochromic behaviors in a discrete layered trinuclear NiII complex. Mechanochromism is the phenomenon observed in certain solid materials where their color change due to the stimulus of mechanical force, such as grinding or pressure. This fascinating property has applications in various fields, such as science, engineering and even art. Mechanochromic materials have garnered interest for their potential applications in sensors, data storage, and information encryption due to their unique properties. Vapochromism refers to the reversible or irreversible phenomenon observed in certain materials where their color change due to the adsorption of vapors or gases of volatile organic amines (VOAs). These gas molecules interact with the material, causing the color change. This effect is typically reversible, meaning that the material returns to its original color through treatment such as heating or recrystallization. This fascinating discovery holds potential applications in chemical sensors, light-emitting diodes and environmental monitors. VOAs can enter the human body through the respiratory tract, skin, and diet, causing discomfort when certain thresholds are exceeded and potentially leading to poisoning or even death in severe cases. As such, detecting and analyzing VOAs is a key area of research in modern analytical chemistry, vital for maintaining a healthy and safe living environment. These compounds are prevalent in biochemical, environmental, and food samples. Despite their simple structure, they play a crucial role in drug design and evaluation, clinical testing and treatment and food regulation. In recent years, with the continuous improvement in quality of life, the demand for health has increased, making human health a constant concern. Problems caused by VOAs have drawn increasing attention because many VOAs are harmful or even carcinogenic. Thus, developing sensitive methods to detect and monitor VOAs that are simple, effective, real-time and low-cost is of great importance for protecting human health. Sensing-based detection methods such as "electronic nose" and "electronic tongue" have recently provided innovative approaches for rapidly and conveniently detecting mixed molecule analytes. Unlike traditional single-component analysis, these methods consider complex mixtures as a whole, using integrated sensing signals for identification analysis, making the process fast and efficient. However, they require complex post-data processing and pattern recognition techniques to gather sufficient information, often struggling to distinguish structurally similar components due to the lack of precise chemical recognition. The advent of colorimetric sensors has addressed this issue by offering a solution that overcomes these limitations. In this thesis, these limitations will be overcome by proposing research aimed at developing a new process for designing sensors with chromic multifunctionality using a trinuclear NiII complex. Although stimuli-responsive chromic materials have been extensively documented, exploration of mechanochromism and vapochromism in NiII compounds is scarcely covered in the literature and continues to pose a significant challenge. To achieve the main objective of this thesis, the following aspects were addressed: 1) An organic ligand containing nitrogen and oxygen atoms is selected to construct the framework. 2) Novel colorimetric sensor based on NiII complex is prepared using the synthesized ligand, forming colorimetric sensor that exhibits color changes upon exposure to different VOAs. 3) A qualitative study of the colorimetric sensor is conducted using a smartphone to analyze the coexistence of mechanochromism and selective vapochromism phenomenon when the NiII complex is exposed to various VOA gases at room temperature (e.g., methylamine, dimethylamine, trimethylamine, ethylamine, and propylamine). The color change can be observed with the naked eye. 4) Comparative studies on the crystallinity, morphology, and composition of the nickel complex will be performed by examining the chromic phenomena and growing single crystals in the presence of different VOAs. This type of colorimetric material could offer broad selectivity for a range of hazardous volatile amine gases, opening up opportunities for the development of a new generation of portable electronic nose systems that operate at room temperature, enabling measurement of meat freshness. Various analytical techniques were employed to study the mechanochromism and vapochromism phenomena of the NiII complex, including single crystal X-ray diffraction, PXRD, NMR spectroscopy, FT-IR, elemental analysis, HRMS and UV-vis spectroscopy.