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Research Project Design, Synthesis, Properties and Applications of Novel Processable Luminescent and Redox Active CompoundsLuminescence is the emission of electromagnetic radiation (in ultraviolet (UV), visible (Vis) or infrared (IR) regions) with no or little heat, which is produced by the transition of an electronically excited state intermediate generated by the application of an external stimuli to a lower (ground) state in order to release the excess energy. If the electronically excited state returns to the ground state from the lowest singlet excited state, it is called fluorescence or if it returns from the triplet excited state, it is called phosphorescence. The light emitted may be in UV and Vis regions as well as in IR region. Luminescent compounds have recently attracted considerable attention due to their practical applications in bio- and nanotechnological as well as materials sciences as chemosensors, electron and/or energy transfer systems, imaging agents, molecular machines and devices, molecular logic gates and so on. For that reason, the design, synthesis and characterization of novel luminescent compounds are highly concerned by first the synthetic organic chemists and as well as other communities all around the world. Herein, luminescent and redox active novel compounds (1-3) were designed, synthesized and characterized spectroscopically (UV-Vis, luminescence-fluorescence, FTIR, NMR, mass spectroscopy, combustion analysis, cyclic voltammetry). Furthermore, some applications of these novel compounds in analytical and/or material science (e.g. in forensic science, chemosensors) were investigated. In the last step of the work, these novel compounds were polymerized to give the corresponding polymeric materials, which were also characterized by spectroscopic methods.Research Project Synthesis of New Benzotellurodiazole Based Inorganic-Organic Hybrid Electroactive MonomersIn this study, the synthesis, characterization and polymerization of six different electron donor-acceptor-donor (D-A-D) type monomers based on benzotelluradiazole and benzimidazole units were tried to be reported. Whereas benzotelluradiazole based D-A-D monomers couldn’t synthesized successfully, benzoimidazole based D-A-D monomers were successfully synthesized, characterized and polymerized electrochemically. Just as benzothiadiazole and benzoselenadiazole analogues, polymers bearing benzimidazole acceptor units combined with thiophene and 3,4-alkylenedioxythiophenes donor units have narrow band gaps in a range between 1.50 eV and 1.57 eV, and showed electrochromic properties under applied external potentials. On the other hand, the applied procedures reported previously elsewhere for benzotelluradiazole analogues did not work for the synthesis of benzotelluradiazole based D-A-D monomers in this study. Unfortunately, the procedures in literature used for the transformation of the polymers containing benzothiadiazole or benzoselenadiazole units into the polymer bearing benzotelluradiazole units also did not work for the monomers and oligomers. Conversely, theoretical studies showed that the synthesis of benzotelluradiazole based D-A-D type monomers and oligomers are stable substances at room temperature and they can give lower band gap polymers when compared to their other electron acceptor analogues. As a result, in order to synthesize benzotelluradiazole based monomers, unlike known procedures, new strategies and procedures must be applied. Work in this line is in progress.Research Project Design and Synthesis of Novel Compounds Based on Donor-Acceptor Systems and the Applications of Their Conducting PolymersConducting polymers continues to facinate many scientists and to become the subject of many researchs in technological and academic areas. The reason for the popularity of the conducting polymers is that they trigger the development of advanced technological materials. Bearing in mind that, desired properties (processability, stability, conductivity, optical properties and so on) of these materials depend on the design and the synthesis of starting monomers. The conducting polymers obtained from the marvellous monomers can be amenable to practical use: (bio)sensors, artificial muscles, displays, electrochromic, memory and photovoltaic devices, supercapacitors, solar cells, light emitting diodes, etc. In this study, the design, synthesis and chemical and/or electrochemical polymerization of monomers (1-6) which are necessary for the generation of processable, low band gap, environmetally stable, reversible electronic and optical properties during n- and p-type dopings, fast switching of the electronic states and different hues of various colors and novel conducting polymers based on donor-acceptor-donor system. Selenium and/or oxygen atoms will be used instead of sulfur atom in benzothiodiazole unit known as acceptor unit in literature. When compared to sulfur, selenium is less electronegative and has larger size, which will obviously affect the electronic and optical properties of obtained conducting polymers. The polymers can be used as RGB (red, green, blue) displays due to green color in its neutral state and transparency in its oxidized state, as supercapacitors due to large and fast doping/dedoping capability, as solar cells due to absorption bands in the region of UV-vis, as photovoltaic devices and radar system due to the high absorption/transmittance values and the emission bands beyond NIR region, as antistatic coatings due to high transparency in the oxidized state, and as n-/p-type transistors due to their reversible and stable n- and p-type dopings. Also, some pre-works on the monomers studied in this project showed that one of the conducting polymers has green color and the modification on the monomer structure of this polymer can open a new door for the discovery of cyan color in the CMY (cyan, magenta, yellow) color system. In this project, initially the monomers (1-6) mentioned above, which is the basic unit for the polymers to be useful in the desired applications, wil be designed, synthesized and characterized. After the characterization of the monomers (by NMR, elemental analysis, FTIR, mass, UV-vis, X-Ray and voltammetric techniques), they will be polymerized into suitable medium via chemical and/or electrochemical polymerization methods. Then, the electronic and optical properties of the obtained conducting polymers will be characterized to be amenable for use in RGB displays, solar cells, supercapacitors, photovoltaic devices, transistors and so on).Research Project Synthesis of Electroactive Chemiluminescent Compounds and Polymers for Blood Detection in ForensicCombination of pyridazine based and chemiluminescent units with electroactive compounds and conjugated polymers have been taken place recently. These compounds and conjugated polymers have been reported to be used instead of luminol in order to detect blood traces in forensic science. These studies resulted in the birth of a new series of compounds so-called “luminol-type compounds”. In this study, a new series of chemiluminescent and conjugated trimeric compounds bearing pyridazine ring (Scheme 1) and their polymers will be synthesized and characterized structurally. Then, their chemiluminescent properties and forensic applications (blood detection) will be scrutinized. Scheme 1. Chemical structure of the compounds bearing redox active terminals and chemiluminescent pyridazine units In order to achieve this aim, phthalic anhydride will be utilized to synthesize the target molecules in three steps. This will be advantageous when compared the synthesis of some luminol derivatives which require multiple steps. After the completion of the structural characterization of the compounds, the chemiluminescent reactions of the compounds in basic medium will be tested firstly in the presence of only hydrogen peroxide and then together with various metal cations as catalyst by using a photomultiplier tube. If iron ion is found to exhibit a catalytic role in the chemiluminescent process, the application of blood trace detection in forensic will be studied. First of all, hemin as a hemoglobin analogue will be used to get a standard curve and then the blood samples will be studied. Obtained data will be compared with luminol and its derivatives and also the effect of the substituents (electron donating units: furan, thiophene and selenophene) of the compounds on the chemiluminescent process will be investigated. Next step will be the electrochemical polymerization of the compounds. The structural analyses of the polymers will be studied by using voltammetric and spectroscopic methods (cyclic voltammetry, NMR, FTIR, UV-vis, SEM, GPC, etc.). Chemiluminescent properties and forensic applications of their polymers will also be studied. Furthermore, since the polymers can be obtained as films via electrochemical polymerization, the electrochemiluminescent properties of these polymers will also be investigated. In addition to the polymers’ structural characterization, their electrochemical and optical properties will be studied to search for their possible opto-electronic applications. When the project has reached to its aims, a new series of the chemiluminescent compounds will be synthesized after only a few steps by starting with a cheap compound called phthalic anhydride. Unfortunately, the interest of the present luminol type compounds in the literature is limited since they are synthesized in multiple steps. A new series of the compounds will be obtained for the family of luminol type compounds when the syntheses of the compounds are realized. Due to the systematic synthesis of the compounds (Group 6A: O (furan), S (thiophene), Se (selenophene) atoms used for the same template compound), the effect of the electron donating units will be investigated on the chemiluminescent property. In conclusion, new compounds that are alternative to the luminol used in forensic application will be brought into the literature.Research Project Synthesis and Applications of High Sulfur Content Polymeric MaterialsSulfur has been used in various applications. With approximately 70 million tonnes produced each year from petroleum refining, elemental sulfur is widely available and inexpensive (∼$120 USD per tonne). A significant portion of sulfur is used in the production of sulfuric acid. Although elemental sulfur is not toxic, it is a flammable solid so finding productive uses for this stockpiled material under the open air is important. Finding large-scale uses for this sulfur, such as conversion to useful polymers, would be an important advance. Polymerization of elemental sulfur has long been studied. Sulfur polymerizes above 159 oC. Unfortunately, the polymeric sulfur undergoes depolymerization since elemental sulfur is more stable thermodynamically at room temperature. As a solution for this problem, in Pyun’s pioneering study, an alkene was used as an organic cross-linker via inverse vulcanization method. In this study, sulfur was heated to 185 °C to initiate ring-opening polymerization and then, addition of alkene resulted in cross-linking. Because of the high sulfur content (50-90 wt%) and the corresponding polysulfur copolymers represented several interesting chemical, material, and optical properties: redox acitivity (cathode materials for Li-S batteries), a high refractive index and a mid IR region of transparency (night vision, thermal imaging), self healing, heavy metal ions remediation, etc. These usage areas have inspired further exploration of inverse vulcanization with a variety of unsaturated cross-linkers to obtain polysulfides with various properties. On the other hand, today vegetable oils are the most important renewable raw material for the chemical industry. About 80% of the global oil and fat production is vegetable oil. These oils make highly pure fatty acids available such as oleic acid (OA) from sunflower, linoleic acid (LA) from soybean, linolenic acid (LnA) from linseed, and ricinoleic acid from castor oil (Figure 1.1(a)). Vegetable oils are expected to play a key role during the 21st century to synthesize polymers from renewable sources. Within this contribution, the project is aimed at the synthesis and application of new high sulfur content polymeric materials using fatty acids (Figure 1.1(a)). Figure 1. (a) Chemical structures of some fatty acids, (b) the synthesis and chemical modification (poly(S-r-OA)-PE) of a polsulfur copolymer (poly(S-r-OA)) via inverse vulcanization. Due to the presence of double bonds, these pure fatty acids will be used firstly for cross-linking by using inverse vulcanization method (Figure 1.1(b)). Correponding copolymers are expected to be soluble in common organic solvents, processable and electroactive. In particular, the effect of double bonds and the free alkyl chains on the polysulfur copolymers will be investigated systematically by using OA, LA and LnA. Another feature of the copolymers obtained from these fatty acids will be the presence of reactive functional units (-COOH), which makes it possible to make chemical modifications (amide, ester, etc. linkages) of the polysulfur copolymers and to convert them into new polymers with different properties. With this project, the first examples of high sulfur content derivatives of polyesters and polyamides (like poly(S-r-OA)-PE) may have been synthesized by the chemical modification (esterification and amidation) of polysulfur copolymers. After inverse vulcanization process, the characterization of the obtained polysulfur copolymers will be done by using NMR, Raman, FTIR, UV, GPC, SEM, DSC, TGA etc., techniques. Electrochemical, optical, and material properties of the polymers will be investigated and tested as potential promising materials for use in Li-S batteries, heavy metal ions remediation and photocatalytic dye removal. The properties of obtained polymers will be compared with each other as well as with the literature data. Lastly, studies will be carried out to produce polymers in kg scale, and the applicability of the method to be applied to the industry will be tested. With reaching the project targets, it will be possible to polymerize elemental sulfur with the renewable vegetable fatty acids; therefore, huge amounts of sulfur can be used more effectively and an important step for sustainable synthesis/production in the polymer industry will be realized.
