LEE- Kimya-Yüksek Lisans

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http://hdl.handle.net/11527/19352

Gözat

Yazar "Aydoğan, Abdullah" ile LEE- Kimya-Yüksek Lisans'a göz atma
  • Öge
    Calix[4]pyrrole based supramolecular polymers via orthogonal interactions
    (Graduate School, 2022-02-07) Budak, Ayşegül ; Aydoğan, Abdullah ; 509191205 ; Chemistry
    Supramolecular polymers are based on reversible intermolecular interactions. Rather than linking the monomers in the desired arrangement via a covalent of polymerization reaction, the monomers are designed in such a way that they self-assemble autonomously into the desired structure. The type and strength of non-covalent interactions varies, ranging from very weak Van der Waals interactions, π-π stacking, hydrogen bonding, solvophobic interactions to dipole-dipole interactions and very strong metal-ligand or ion-ion interactions. A well-known natural supramolecular system is DNA, whose unique architecture results from cooperative non-covalent interactions, such as multiple hydrogen bonds and hydrophobic interactions. By exploiting the reversibility of the interactions, materials with fascinating properties such as self-healing, shape memory and responsive behaviour can be produced. These materials have been prepared by using cationic guests and the host molecules that can interact with these guests and found various applications in energy, regenerative medicine, nanotechnology, environment and synthetic chemistry. Calix[4]pyrroles are non-conjugated tetrapyrrolic macrocycles capable of binding anions and neutral substrates in organic media via hydrogen bonding. Moreover, upon anion binding, they change their conformation from 1,3-alternate to cone conformation to facilitate the hydrogen bonding. Apart from that, cation-π interaction between appropriate cations and π-electron cloud of cone-shaped calix[4]pyrroles are also well known. Non-covalent and reversible supramolecular interactions provide functional materials within one polymer system. These specific interactions can be designated independently and simultaneously giving orthogonal self-assembly. The aim of this thesis is to synthesize and characterize supramolecular polymers based on anion recognition chemistry of calix[4]pyrroles via orthogonal self-assembly. In this thesis pyrimidinone functionalized calix[4]pyrrole derivative (UPyCP2) and a bis-carboxylate (TBAS) salt were used as host and guest molecules, respectively. Another supramolecular polymeric system was also prepared by host-guest, cation-π and van der Walls interactions that has been built from a bis-calix[4]pyrrole (BisCP) and bis-carboxylate (CTAS) as host and guest moieties, respectively. These supramolecular polymers prepared in an organic solvent and were found tho have thermo-, chemical-responsive behaviour. The above systems have been analyzed by NMR, viscosity measurements and scanninng electron microscopy.
  • Öge
    Calix[4]pyrrole-based supramolecular assemblies
    (Graduate School, 2024-06-25) Mirabolghasemi, Mana ; Aydoğan, Abdullah ; 509211264 ; Chemistry
    Supramolecular assemblies are known as large-scale and organized structures formed as a result of the self-assembly of smaller molecules through non-covalent interactions such as hydrogen bonding, van der Waals interaction, metal-ion coordination, and cation-π interactions. Within this framework, poly-pseudorotaxanes and micelles are considered as noteworthy examples of supramolecular assemblies that have shown various applications in materials science and drug delivery. The study of such assemblies and attempts to manipulate them to design novel structures can contribute to advancements in these fields. To date, in the field of supramolecular chemistry, numerous macrocyclic structures such as crown ethers, cucurbiturils, calixarenes, and cyclodextrins have been used in the formation of supramolecular amphiphiles and mechanically interlocked molecules. Among these well-known macrocyclic structures, calix[4]pyrrole is known for its remarkable features, including its capability to acquire cone conformation upon binding to an anion, which facilitates ion-pair recognition and anion sensing through hydrogen bonding with anions. Calix[4]pyrrole is a molecule known for its ability to bind various ions in different ways due to its unique conformational features suitable for host-guest interactions. As a result, various types of calix[4]pyrrole systems have been developed to sense or extract ions and can exhibit different binding modes, enabling their use in synthesizing molecular machines. The main goal of this thesis is to demonstrate the applications of calix[4]pyrroles and how they can be used in various areas such as in drug loading and release, in addition to the formation of poly-pseudorotaxane structures, owing to its anion and ion-pair recognition capabilities, respectively. Therefore, in this thesis, we present the innovative synthesis of a non-ionic surfactant built upon the calix[4]pyrrole framework, where a polyethylene glycol (PEG) moiety is introduced at one of its meso positions (C4P-PEG). This surfactant demonstrates the ability to form stable micelles in water. Additionally, it exhibits the capacity to encapsulate a chemotherapeutic cancer drug, doxorubicin hydrochloride (DOX·HCl), by recognizing its counter chloride anion in an aqueous environment. Following the characterization of the synthesized compound using NMR spectroscopy and mass spectrometry, its micelle formation ability in water is confirmed through TEM imaging, DLS and NMR spectroscopy. Furthermore, to assess drug-loading and release capabilities, we employed the nanoprecipitation method and utilized techniques such as TEM and DLS for characterization. Lastly, UV-vis spectroscopy is conducted to determine the compound's drug loading capacity, and its release behavior is examined under different pH conditions, revealing a preference for release under acidic conditions. In addition to the pioneering study of drug delivery applications using the anion recognition property of calix[4]pyrrole, we synthesized the bromide salt of pyridinium-functionalized calix[4]pyrrole (1-Br), which can self-assemble into a supramolecular polymer through ion-pair recognition, serving as the axle of a poly-pseudorotaxane, and perethylated pillar[5]arene (EtP5A) was successfully threaded as the wheels. Moreover, in our anion-controllable molecular motions study, we examined the changes in the properties of the proposed poly-pseudorotaxane by substituting bromide ions in 1-Br with fluoride (1-F), chloride (1-Cl), and hexafluorophosphate (1-PF6) ions using different characterization methods.
  • Öge
    Physically cross-linked polymers through anion recognition
    (Graduate School, 2022) Odabaş, Ayşe ; Aydoğan, Abdullah ; 740869 ; Chemistry Programme
    Supramolecular chemistry revolves around relatively small molecular systems that can self-assemble with the assist of highly directional intermolecular interactions such as metal coordination, host guest inclusion, hydrogen bonds, π-π stacking and supported with non-directional ones such as van der Waals forces, hydrophobic interactions. Reversible nature of these systems allows for shape memory, self-healing, and stimuli responsiveness. Self-assembly process of supramolecular systems can be manipulated to be stimuli responsive to UV light, pH and temperature and concentration variations. Designing materials with self-assembling properties creates opportunities for wider application of low molecular weight monomers and even covalently bonded polymer chains. Some of the application areas include drug-release systems, ion sensors, bio-compatible materials, thermo-responsive adhesives, and coatings. Main caveat of this dynamic nature and mobility can result in materials with low thermodynamic stability but it can be improved via utilizing various secondary interactions simultaneously. A Calix[4]pyrrole skeleton consists of four pyrrole rings bridged by methylene at 2, 5 positions and functionalized by total of 8 methyl substitutions at meso-rim to form a non-conjugated macrocyclic structure. It can switch between four possible conformations, 1,3 alternate, 1,2 alternate, partial cone and cone. Cone conformation provides the most ideal environment for ion binding as quadruple directional hydrogen disposition on nitrogen atoms enables a relatively attractive site towards anions, neutral substrates, and anion-cation pairs. Supramolecular polymers with host-guest interactions have seen enthusiastic interest on cationic guest species and anionic congeners have recieved relatively less attention. Supramolecular polymerization can be self-induced via hydrogen bonding and mechanical properties can be further reinforced by pseudo cross-linking in the form of host-guest complexation with anionic species, which might allow a construct similar to polymer gel networks. Utilizing the same principle on polymer chains may provide the formation of physical cross-linking between polymer chains, resulting in the construction of supramolecular polymer gels. This study has two focuses, both stemming from the utilization of anion recognition chemistry of calix[4]pyrroles to design reversibly cross-linked materials in organic media. A bis-ureido pyrimidinone functionalized calix[4]pyrrole (Bis-UPyC4P) unit and a bis-carboxylate ((TBA)2Terepthalate) were used, as host and guest moieties respectively, for supramolecular networks. Another approach was taken with calix[4]pyrrole units as a part of a polyurethane polymer backbone (P-C4P) and a bis-carboxylate ((TBA)2Suberate) to form supramolecular polymer gel networks. P-C4P was also utilized in liquid-liquid extraction studies of anions. Both Bis-UPyC4P and P-C4P materials have shown increased viscosity in the presence of bis carboxylate salts as well as thermo-responsiveness. P-C4P was relatively successful at extraction studies. These systems were analyzed by NMR spectroscopy, viscosity and conductivity measurements, UV-VIS spectroscopy, and rheological analyses.