Beyaz ışık oled uygulamarı için tiyenotiyofen ve tetrafeniletilen içeren moleküllerin sentezi
Synthesis of thienotiophene and tetrafenyethylene for white light oled applications
Yazar: FATMA ELİF ALACACI
Danışman: PROF. DR. TURAN ÖZTÜRK ; DR. ERMAN KARAKUŞ
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Kimya Ana Bilim Dalı / Kimya Bilim Dalı
Derece: Yüksek Lisans, 2021
Konu: Kimya = Chemistry

Özet:
Organik elektronik ve optoelektronik malzemeler günümüz teknolojisinin uygulama alanları içinde önemli ve etkin bir yere sahiptirler. Optoelektronik alanında yürütülen temel araştırmalar yeni nesil yarıiletken malzeme sistemlerine dayalı cihaz ve mekanizmaların geliştirilmesine yöneliktir. Organik moleküller düşük maliyetleri, kolay işlenebilirliği ve farklı yüzeylere kolaylıkla uygulanabilme özelliğinden dolayı, organik ışık yayan diyotlar (OLED), alan etkili transistörler (OFETs), organik güneş pilleri (OSCs) ve organik fotovoltaikler (OPVs) gibi çeşitli optoelektronik cihazlara başarılı bir şekilde uygulanmaktadır. 
Moleküller sahip oldukları özelliklerden dolayı göstermiş oldukları emisyon ve absorpsiyon gibi davranışlar, bu moleküllerin kullanım alanlarını belirlemektedir. OLED için kullanılan ve sentezlenen organik malzemeler içindeki fonksiyonel gruplar sayesinde floresans, elektroluminesans özellikler kazanmıştır. Bu sebeple OLED için bu özelliklerle donatılmış birçok materyal dizayn edilmiştir. 
Organik ışık veren cihazların (OLED) yapımında yeşil, kırmızı ve mavi gibi farkı renklerde ışık veren OLED`ler yapılmıştır. Ancak, beyaz ışığı elde etmek oldukça zor olmuştur. Çünkü beyaz ışık elde etmek için uygulanan en bilinen yollardan biri farklı renklerde (yeşil, kırmızı ve mavi) ışık veren floresan malzemelerin aynı anda uyarılarak beyaz ışık vermesi sağlanmaktadır. Bu şekilde beyaz ışık elde etmek için farklı renk veren organik polimerlerin cihaz içinde sırasıyla katman olarak kaplanması gerekmektedir. Ancak, OLED yapımında bu teknik oldukça uzun sürmektedir. Ayrıca, polimerlerin çözünürlüklerinin farklı çözücülerde değişmesi cihaz üretimini de büyük ölçüde kısıtlamaktadır. Bu sebeple cihazın verimini, ömrünü ve üretimini artırmak için yeni yöntemler araştırılmıştır. 
Bu yöntemler içerisinde çeşitli optoelektronik uygulamalar için materyallerin tasarımında kullanılan donör (D, verici) akseptör (A, alıcı) içeren konjüge organik moleküller en etkili olandır. D-A sistemlerinde HOMO-LUMO arasındaki band aralığının düşük olması önemlidir. Çünkü aradaki enerji farkının az olması, iletkenliğin fazla olduğunu gösterir bu durum cihazın verimliğinin artması anlamına gelmektedir. 
Donör olarak sistemimizde, kükürt üzerindeki ortaklaşmamış elektron çiftlerinin halkaya kolayca sunulmasında dolayı Tiyeno[3,2-b]tiyofen kullanılacaktır. Tiyofen halkası elektronca zengin, kolay modifikasyonları, yüksek kimyasal ve termal kararlılıklarından dolayı D – A sistemlerinde kullanımı oldukça yaygındır. Materyal kimyasında optoelektronik uygulamalar için, Tiyenotiyofen ve türevleri olan bileşikler yaygın olarak kullanılmaktadır. Grubumuz tarafından daha önce yapılan çalışmalarda görülmüştür ki, TT ve türevlerini içeren optoelektronik materyallerin sentezleri etkin bir rol oynamaktadır. Bu sebeple TT donörü bu çalışmadaki en önemli yapıtaşlarından bir tanesidir.
Tetrafeniletilen (TPE) molekülü organik çözücü içerisinde ışıma göstermez. Ancak katı halde şiddetli bir ışıma gösterir. Bunun sebebi olarak hareketli olan fenil gruplarının çözelti içerisinde hareket ederken, katı halde bu hareket mümkün olmadığı için katı halde ışıma gösterir. Bu olaya Topaklanmaya Bağlı Işıma (Aggregiation Induced Emission, AIE) olarak adlandırılır. Işık yayan diyotların yapımına katılmasından dolayı materyal kimyası için önemli bir yere sahiptir.
Üç koordine bor atomunun boş pz orbitali ile komşu π-orbitalinin örtüşmesiyle elektron çekici bir özellik kazanmakta ve kuvvetli bir akseptör olmasını sağlamaktadır. Aynı zamanda, π konjuge sistemine katıldığında elektronları delokalize edebilmesi sayesinde π konjugasyonunun uzamasına neden olur. Bu özelliğinden, boron akseptör olarak kullanılacağı polimerlerde; fotoluminesans, elektroluminesans (EL), n-tipi yarı iletken vb. özelliklerine sahip önemli materyallerin geliştirilmesini sağlamıştır. Konjuge organoboron polimerler, geniş uygulama alanları ile malzeme kimyasında yeni bir uygulama alanı oluşturmuş ve organik elektronik ve optoelektronik malzemelerin geliştirilmesinde rol almıştır.
Sunulan bu çalışmada, OLED uygulamalar için alkil grubu içeren tiyenotiyofen ve tetrafeniletilen moleküllerin tasarımı ve sentezi amaçlanmıştır. Bu moleküllerin karakterizasyonları yapılarak, optik ve elektrokimyasal özellikleri incelenmiştir. Bu çalışmada sentezlenen moleküllerin UV-VIS, floresans ve topaklanmaya bağlı ışıma özellikleri incelenip kıyaslanmıştır. Bu çalışmanın sonucunda yeni nesil organik yarıiletken moleküllerin deneysel ve teorik veriler ışığında materyal kimyasına katkı sağlanması amaçlanmaktadır. Ayrıca bu çalışmanın içinde çalışılan moleküllerin daha sonraki çalışmalarda OLED uygulamalarında ile bilimsel ve teknolojik yararlar öngörülmektedir.

Abstract:
Organic electronic and optoelectronic materials have an important and effective place in the application areas of today's advanced technology. Basic research in the field of optoelectronics aims at developing devices based on new-generation semiconductor material systems that meet the needs of developing technology. With their low cost, easy processability and advantages due to their applicability to different surfaces, organic molecules have been applied successfully in various optoelectronic devices such as organic light emitting diodes (OLED), field effect transistors (OFETs), organic solar cells (OSCs) and organic photovoltaics (OPVs).
The behaviors of molecules such as emission and absorption due to their properties determine the usage areas of these molecules. With the functional groups in organic materials used for OLED, it has acquired properties of fluorescence and electroluminescence. For this reason, many materials equipped with these features have been designed for OLED.
OLEDs that emit light in different colors such as green, red and blue were made in the production of devices that produce organic light. However, obtaining white light in one step has been quite difficult. One of the most common ways to obtain white light is through the simultaneous excitation of fluorescent materials that emit light in different colors (green, red and blue), thereby resulting in white light. In order to obtain white light in this way, organic polymers that emit different colors must be coated in the device as layers. But, this is a lengthy process for OLEDs. In addition, the varying solubility of polymers in different solvents greatly restricts device production. For this reason, new methods have been studied to increase the efficiency, durability and production of the device.
Conjugated organic molecules containing a donor (D, donor) and an acceptor (A, acceptor) are one of the most effective methods used in designing materials for various optoelectronic applications. In such system, it is important that HOMO-LUMO band gap is low. This is because a lower band gap increases conductivity and this extends the lifetime of the device. 
This system uses Thieno [3,2-b] thiophene (TT) as a donor molecule as uncoupled electron pairs on sulfur are easily transferable to the ring. Thiophene rings are widely used in molecules containing D A as they are electron-rich, easily modifiable and have high chemical and thermal stability. Thieno [3,2-b] thiophene (TT) derivatives are widely used in material chemistry as donor compounds and has been synthesized by this group. The TT donor is one of the most important building blocks that will take place in our system.
Tetraphenylethylene (TPE) does not display emission in organic solvents because of the free rotation of phenyl groups. On the other hand, it has a strong fluorescence property in its solid state due to Aggregation-Induced Emission (AIE). Thus, it is widely used in various organic materials for solid-state fluorescence applications. It has an important place in material chemistry due to its use in light-emitting diodes.
 It is known that the overlap of the empty pi-orbital of three coordinated boron atoms with the neighboring pi-orbital causes the boron to become a strong acceptor and the pi-conjugation to be elongated. 
Because of this feature, it has enabled the development of important materials that have the properties of photoluminescence, electroluminescence (EL) and can be used as n-type semiconductors in polymers where they are used as boron acceptors. Conjugated organoboron polymers have created a new application area in material chemistry with their wide application areas and have been involved in the development of organic electronic and optoelectronic materials.
This study aims to design and synthesize alkyl group containing thienothiophene and tetraphenylethylene molecules for OLED applications. It will characterize these molecules and investigate their optical and electrochemical properties. For this reason, it studied the molecules' UV-VIS, fluorescence and Aggregation-Induced Emission (AIE) properties. It had originally sought to synthesize polymers from TT-alkyl groups and TPE (tetrapheylethene). It aims to contribute to the material chemistry of next-generation organic semiconductor molecules in light of experimental and theoretical data. Also, this study is expected to benefit future research with its scientific and technological findings.
	Synthesis of 1-(thiophene-3-ylthio)octan-2-one (20a) 3-Bromothiophene (3.00 g, 18.4 mmol) was solved in 50 mL dry dietyl ether in 3 neck flask under N2 atmosphere. When the reaction temperature fell to 78°C below zero, 2.5M n-BuLi (8.1 mL, 20.2 mmol) was added to the reaction mixture. Elemental sulphur (647mg, 20.2 mmol) was added 45 min later and stirred for 30 min, after which the  device was shut off. The reaction temperature increased to 30°C below zero 1-bromo-2-octanone (4.19g, 20.2 mmol) was added. The reaction was stirred overnight under N2 atmosphere. After quenching the reaction, it was extracted with dicholomethane and a solution of  NaHCO3 %10 and water. The organic phase dried with Na2SO4 and the solvent was evaporated under atmospheric pressure. After adding n-hexane in the product, it was placed in the freezer where it crystalized. Having spent one night in the freezer, 1.60 g of pure white crystals were obtained with a yield of 36%. 
	Synthesis of 1-(thiophene-3-ylthio)undecan-2-one (20b) 3-Bromothiophene (3.00 g, 18.4 mmol) was solved in 50 mL dry dietyl ether in 3 neck flask under N2 atmosphere. When the reaction temperature fell to 78°C below zero, 2.5M n-BuLi (8.09 mL, 20.2 mmol) was added drop-by-drop to the reaction mixture.
After stirring the reaction for 45 min, elemental sulphur (645mg, 20.2 mmol) was added. The  device was shut off after stirring for 30 min at this temperature. Then, 1-bromo-2-undecanone (4.19 g, 20.2 mmol) was added at 30°C below zero. The reaction was stirred overnight under N2 atmosphere. After the quenching of the reaction, it was extracted with dicholomethane and a solution of  NaHCO3 %10 and water. The organic phase was dried with Na2SO4 and the solvent was evaporated under atmospheric pressure. The product was purified via column chromatography over silica gel using n-hexane as an eluent. 3.10 g of a pure brown oily product were obtained with a yield of 60%. 

	Synthesis of 3-hexylthieno[3,2-b]thiophene (21a) Polyphosphoric acid (2.4 g, 24.75 mmol) and 5 mL of chlorobenzene were put in a round bottomed flask. This mixture heated up to 135°C. 1-(thiophene-3-ylthio)octan-2one (20a) (400 mg, 1.65 mmol) was solved in 5 mL chlorobenzene and then added to the mixture dropwise. The reaction was stirred for 48 hours. Clorobenzene phase was separated to the PPA phase. After chlorobenzene evoporated, extracted with  dicholomethane and a solution of  NaHCO3 %10 and water. The organic phase was dried with Na2SO4 and the solvent was evaporated under atmospheric pressure. The product was purified via column chromatography over silica gel using n-hexane as an eluent. 346 mg of a pure colorless liquid product were obtained with a yield of 93%. 
	Synthesis of 3-Nonylthieno[3,2-b]thiophene (21b) Polyphosphoric acid (1.35 g, 13.81 mmol) and and 5 mL of chlorobenzene were put in a round bottomed flask. This mixture heated up to 135°C. 1-(thiophene-3-ylthio)undecan-2-one (20b) (262 mg, 0.9 mmol) was solved in 5 mL chlorobenzene and then added to the mixture dropwise. The reaction was stirred for 48 hours. Clorobenzene phase was separated to the PPA phase. After chlorobenzene evoporated, extracted with  dicholomethane and a solution of  NaHCO3 %10 and water. The organic phase was dried with Na2SO4 and the solvent was evaporated under atmospheric pressure. The product was purified via column chromatography over silica gel using n-hexane as an eluent. 206 mg of a pure colorless liquid product were obtained with a yield of 84%. 
	Synthesis of 2-Bromo-3-hexylthieno[3,2-b]thiophene (22a) 3-hexylthieno [3,2-b]thiophene (21a) (200 mg, 890 μmol) and DMF (4-5 mL) were put in a  round flask which was protected from light. The flask was then placed in an ice bath. NBS (166 mg, 935 μmol) was added to the reaction 10 min later. After 12 hours, the reaction was quenched with a saturated NaHCO3 -water solution and extracted with dichloromethane. The organic phase was dried with Na2SO4 and the solvent was evaporated under atmospheric pressure. The product was purified via column chromatography over silica gel using n-hexane as an eluent. 256 mg of a pure colorless oily product were obtained with a yield of 95%.
	Synthesis of 2-Bromo-3-nonylthieno[3,2-b]thiophene (22b) 3-nonylthieno [3,2-b]thiophene(21b) (200 mg, 750 μmol) and DMF (4-5 mL) were put in a  round flask which was protected from light. The flask was then placed in an ice bath. NBS (140 mg, 780 μmol) was added to the reaction 10 min later. After 12 hours, the reaction was quenched with a saturated NaHCO3 -water solution and extracted with dichloromethane. The organic phase was dried with Na2SO4 and the solvent was evaporated under atmospheric pressure. The product was purified via column chromatography over silica gel using n-hexane as an eluent. 238 mg of a pure colorless oily product were obtained with a yield of 92%.
	Synthesis of 1,2-bis(4-bromophenyl)-1,2-diphenylethene (24) 
4-bromobenzophenone (23) (4.00 g, 15.3 mmol) and Zinc powder (3.15 g, 30.6 mmol) were put in a 3 neck flask under N2 pressure. Adding 50 mL of anhydrous THF, the reaction was refluxed. Once the reaction was cooled to 78 °C below zero, TiCl4 (1.26 mL, 23.0 mmol) was added dropwise. The cooler instrument was then shut down and the reaction was mixed at room temperature for 30 min.  Following this step, it was mixed for 24 hours in the reflux system. After the reaction quenching with solution of K2CO3 %10and water, it was extrated with dichloromethane. The organic phase was dried with Na2SO4 and the solvent was evaporated under atmospheric pressure. The product was precipitated by being added dropwise on the cold methanol. 2.60 g of a white solid product were obtained with a yield of 70%.
Synthesis of 1,2-diphenyl 1,2-bis(4-(4,4,5,5-tetrametyl-1,3,2-dioxaborolane-2-il)phenyl)ethene (26) 1,2-bis(4-bromophenyl)-1,2-diphenylethene (24) (500 mg, 1.01 mmol), bis(pinacolata)diboron (25) (543 mg, 2.14 mmol), potassium acetate (300 mg, 3.06 mmol) and as a catalyst PdCl2dppf (23.0 mg, 31,8 μmol) were placed two necked round flask in a vacuum. After adding anhydrous 1,4 dioxane (40 mL), the reaction was refluxed overnight under N2 pressure. The reaction was cooled to room temperature and it was extracted with the saturated NaHCO3 -water solution and dichloromethane. The organic phase was dried with Na2SO4 and the solvent was evaporated under atmospheric pressure. The product was precipitated by being added dropwise on the cold methanol. 310 mg g of a white solid product were obtained with a yield of 52%.
	Synthesis of (E)1,2-bis(4-(3-hexylthieno[3,2-b]thiophene-2-yl)pheyl)-1,2-dipheylethene (27) 2-Bromo-3-hexylthieno[3,2-b]thiophene (22a) (260 mg, 850 μmol) and  1,2-diphenyl 1,2-bis(4-(4,4,5,5-tetrametyl-1,3,2-dioxaborolan-2-yl)phenyl)ethene (26) (238 mg, 408 μmol) were placed in a Suzuki coupling reactor. A solution of 2 M  K2CO3, 2 mL DMF and 8 mL Toluene were added into the reactor which was under a N2 atmosphere. The reactor was saturated with N2 and Pd(0)(PPh3)4 (48.0 mg, 42.0 μmol) was added as a catalyst. The reaction was stirred 110 °C for 48 hours. After cooling to room temperature, the reaction was filtered through celite. The product was purified by silica colomn chromotography using n-hexane/dichloromethane at a ratio of  (1 : 3). 
	Synthesis of 1,2-bis(4-(3-nonylthio[3,2-b]thiophene-2-yl)phenyl)-1,2-diphenylethene (28) 2-Bromo-3-nonylthieno[3,2-b]thiophene (22b) (200 mg, 579 μmol) and 1,2-diphenyl 1,2-bis(4-(4,4,5,5-tetrametyl-1,3,2-dioxaborolan-2-yl)pheyl)ethene (26) (161 mg, 275 μmol) were placed in a Suzuki coupling reactor. A solution of 2 M  K2CO3, 2 mL DMF and 8 mL Toluene were added into the reactor which was under a N2 atmosphere.  The reactor was saturated with N2 and Pd(0)(PPh3)4 (33.0 mg, 29.0 μmol) was added as a catalyst. The reaction was stirred 110 °C for 48 hours. After cooling to room temperature, the reaction was filtered through celite. The product was purified by silica colomn chromotography using n-hexane/dichloromethane at a ratio of  (1 : 3).