Synthesis and applications of supramolecules and macromolecules containing multiple triazole units

Abstract

Triazole derivatives are cyclic structures with the closed formula of C2H3N3 consisting two different isomers namely, 1,2,3-triazole and 1,2,4-triazole. Their distinctive qualities including anti-microbial, anti-cancer, anti-epileptic, anti-inflammatory and anti-viral properties make them employable in drug designs and attrached the interest of scientists across the globe. As an indication of this interest, last year's Nobel Prize was awarded to Prof. Sharpless for his works on "Click Chemistry" focusing on triazoles, as an easy linker group for several applications. While there are numerous green methods to synthesize triazoles, being environmentally friendly itself, it can offer new horizons to organic chemists to develop novel approaches. Additionally, their long shelf life and highly efficient yet straightforward reaction conditions allow them to be synthesized in larger amounts and made them popular in several research areas. In this thesis, we aimed to synthesize novel supramolecules and macromolecules containing more than one triazole ring and to investigate the possible applications of the resulting structures. In the first chapter, the aim of the thesis, the scientific novelty and the topics of each chapter are briefly discussed. The second chapter focuses on the synthesis of dibenzoxanthene derivatives that possess triazole rings. Dibenzoxanthenes have extensive utility in the field of metal ion sensing applications. Fluorescent dibenzoxanthene derivatives exhibit significant guarantees as candidates for the detection of metal ions across different solvent systems. Nevertheless, the majority of research conducted thus far has mostly concentrated on the detection of metals in aqueous solutions, with a special focus on the identification of very hazardous metal ions, such as lead (II) (Pb2+) and mercury (II) (Hg2+). The present investigation involved the synthesis of a newly developed benzyl-functionalized dibenzoxanthene (BDBX) derivative and a novel fluorescent anthracene functionalized dibenzoxanthene (ADBX) derivative. These compounds were designed to detect metal ions in polar aprotic solvent systems. The detection process employed ultraviolet-visible (UV-Vis) spectroscopy and fluorescence spectroscopy techniques. The compound benzyl dibenzoxanthene exhibited sensitivity towards several metal ions, namely lead II (Pb2+), cobalt II (Co2+), and copper II (Cu2+). In contrast, the newly synthesized anthracenyl-dibenzoxanthene compound demonstrated sensitivity exclusively towards Cu2+ ions. Notably, each anthracenyl-dibenzoxanthene molecule exhibited a binding capacity for three Cu2+ ions, resulting in an enhanced sensitivity towards copper. The analysis of the affinity for binding between Cu2+ and dibenzoxanthene derivatives has been conducted using proton nuclear magnetic resonance (1H NMR) and high-resolution X-ray photoelectron spectroscopy (XPS). In the third chapter of the thesis, the synthesis of three novel molecular cages is described. These cages are based on a bis-structure derived from 8,16-methano-16H-dinaphtho[2,1-d: 1',2'-g].A compound known as [1,3]dioxocine (DNDO), consisting of interconnected triazole rings, has been reported in the scientific literature. The bis-DNDO structures are connected by linkers that possess both etheric structures and bis(1,2,3-triazole) moieties, which also serve as coordination ligands. The molecular cages' cavities undergo alterations dependent upon the position in space of the oxygen atoms within the dioxolane ring. In chapter four, triazole-containing flame retardants were synthesized. The utilization of contemporary chemical routes and the advancement of inventive material designs offer intelligent resolutions to the challenges experienced in the field of materials science, hence expanding opportunities for future academic studies. In the third study, we used two-click reactions to synthesize a reactive flame retardant that contains phosphorus (P) and nitrogen (N) atoms. The para-fluoro substituents of bis(pentafluorophenyl)phenyl phosphine oxide were subjected to azidation, followed by the subsequent interaction of the resulting product with propargyl acrylate by the use of a copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC). The present study aimed to explore the effect of different concentrations (10%, 20%, and 30%) of a synthetic monomer on the mechanical, thermal, and flame retardancy properties of an aliphatic polyurethane acrylate. The utilization of the recently synthesized monomer resulted in a notable decrease in the conversion rates of double bonds, an enhancement in the tensile strength of the photocured samples, and a decrease in the values of elongation at break values. The observed trend shows an upward correlation between the quantity of the flame retardant monomer and both the glass transition temperatures (Tg) and the limiting oxygen index (LOI) values. A significant improvement of around 25% in the Limiting Oxygen Index (LOI) values was observed when the flame retardant percentage in the formulations approached 30%. In the fifth chapter, in contrast to the fourth, fire-resistant materials were developed using bio-based materials. The use of bio-based building blocks for the synthesis of polymers is increasing day by day. Among the bio-based building blocks, eugenol is a highly promising monomer for the preparation of thermoset materials. In the fourth study, we combined thiol-ene photopolymerization (TEP) and thermal azide-alkyne cycloaddition click reactions to prepare eugenol-based thermally stable, P-, N-, and silicon (Si)-containing networks. To this end, we synthesized a P-containing, eugenol-based monomer-bearing azide group and a siloxane compound containing an alkyne group. By mixing these monomers with multifunctional thiols and by utilizing a dual-curing strategy, we managed to obtain optically transparent and thermally stable coatings with excellent adhesion to glass substrates. The thermal stability, optical transmittance, pendulum hardness, solvent resistance, and adhesion performance of the coatings were evaluated. The gel contents of the thermoset materials were found to be over 95%. At 600oC, the char yields of the dual-cured coatings were found to be over 30%. Coatings were also found to be resistant to acidic and basic conditions as well as solvents. Within the scope of this thesis, several novel molecules containing multiple triazole rings have been synthesized and their possible applications have been investigated. The studies conducted in each section of the thesis have been published in well-respected international scientific journals.