Elektronik ve optoelektronik uygulamalar için siyanofenil tiyenotiyofen ve bor içeren materyaller
Cyanophenyl thienothiophene and boron containing materials for electronic and optoelectronic applications
Yazar: RECEP İŞÇİ
Danışman: PROF. DR. TURAN ÖZTÜRK
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Ana Bilim Dalı / Kimya Bilim Dalı
Derece: Yüksek Lisans, 2017
Konu: Kimya = Chemistry

Özet:
Organik elektronik materyaller ile bunların uygulamaları, özellikle fizik ve kimya alanında bilimsel araştırmacıların artan bir eğilimle ilgi odağı olmuştur. Organik moleküllerin yapılarının kolay değiştirilebilmesi ve bu değişikliğe bağlı olarak organik materyalin özelliklerinin direk olarak değiştirilebilmesi bu artan ilginin ana sebebidir. Organik materyallerin performansı, silikon ve galyum arsenik temelli materyallerin gerisinde kalmasına rağmen, optoelektronik alanında kullanılabileceğinin gösterilmesi ile yeni bir pencere açılmış oldu. Günümüzde organik ince filmlerin pek çok uygulama alanında kullanılabileceği bilinmektedir. Bunlar arasında, renkli ekranlarda kullanılan organik materyallerle organik ışık saçan cihazlar (organic light emitting devices, OLED), organik ince film transistörler ve düşük maliyetli ve etkin güneş pili hücreleri (solar cells) başta gelmektedir. 
Genel olarak elektronik ve optoeletronik cihaz yapımında, küçük organik moleküller ve polimerler olmak üzere iki grup kullanılmaktadır. Bu tür malzemelerin hazırlanmasındaki esas sorun, organik materyalin elektronik yapısını iyi anlayarak yeni yüksek performansa sahip optik ve elektronik cihazların dizayn edilmesidir. Organik molekülün yapısında yapılacak en ufak değişiklikler, molekülün uygulama alanındaki özelliğini büyük oranda değiştirebilmektedir. Günümüzde moleküler düzeyde organik moleküllerin yapısında değişiklikler yaparak elektronik ve optoelektronik malzemelerin özelliklerini değiştirmek son derece zor ve önemli bir konudur. Tiyofen temelli organik materyaller, moleküler mühendislikle, fonksiyonel özelliklerinin kaba ve ince ayar yapılarak değiştirilebilmesinden dolayı ümit vadeden moleküller arasında en üstlerde yer almakta ve birçok araştırma grubu tarafından incelenmektedir.
Organik materyallerden güneş pili uygulamalarında kullanılan ilk etkin hücre, 1954 yılında yapılan %6 verime sahip silikon esaslı pildir. Bu hücre, silikona arsenik katılması ile negatif yüklü silikon (n-dope) elde edilmesi prensibine dayanmaktadır. Günümüzde ise silikon esaslı güneş pillerinin verimi %25 civarına ulaşmış bulunmaktadır.
Organik materyallerin güneş pilleri yapımında kullanılması ile maliyetin düşürülmesi ve geniş çapta üretim yapılması amaçlanmış ve pi-konjuge polimerlerin 1977 yılında Shirakawa, MacDiarmid ve Heeger tarafından bulunması ile bu araştırmalar ivme kazanmıştır. İnorganik yarıiletkenler oda sıcaklığında aydınlatma ile serbest elektronlar ve boşluklar (hole, artı yük) üretirken, organik yarıiletkenler ışığı soğurarak "exciton" adı verilen sıkıca bağlı artı eksi yük çiftini oluşturmaktadırlar. Organik materyaller, düşük dielektrik sabitine sahip olmaları sebebiyle elektron ve boşluk (hole) arasında güçlü "Coulombic" etkileşime yol açarlar. Araştırmaların başında ilk organik güneş pilleri %0.3 gibi düşük dönüşüm sağlamalarına karşın, günümüzde bu materyallerin %13'ün üzerinde dönüşüm performansları gösterdiği görülmektedir. Organik güneş pillerinin inorganiklere göre daha hafif, daha esnek ve düşük maliyetli olmaları daha büyük alanlara uygulanabilmeleri için bu tür materyallerin uygulanmasında büyük avantajlar sağlamaktadır. Bu bakımdan, organik güneş pilleri uygulamaları için yeni organik moleküllerin dizayn ve sentez edilmeleri yönünde büyük çabalar sürmektedir. Bu çabaların önemli nedenleri arasında organik materyallerin çeşitli şekillerde fonksiyonelleştirilmesi ile optik, elektrokimyasal, çözünürlük, morfolojik ve elektriksel özelliklerinin ince bir şekilde ayarlanabilmesi gerekmektedir.
Tezin amacını organik elektronik ve optoelektronik alanda rol oynayacak siyano tiyenotiyofen türevli moleküllerin hem trifenilamin hem de bor içeren materyaller olarak hazırlanması ve özelliklerinin incelenmesi oluşturmaktadır. Bu malzemelerin hazırlanması sentez kimyası ve polimer kimyasını yakından ilgilendirmektedir. Bu açıdan projenin kapsamı borun, güneş pilleri uygulamalarında kullanılabilecek, polimerik olmayan ve donör-akseptör (D-A) üniteleri içeren organik moleküller içerisinde akseptör grup olarak geliştirilmesi ve OLED çalışmaları için yüksek floresans etkiye sahip trifenilamin ile donör grubu olarak grubumuzca geliştirilen tiyenotiyofen (TT) türevi kullanılmasıdır. Böylece materyal kimyasına D-A modelinde TT türevli yeni organik yapılar kazandırılacaktır.

Abstract:
Organic electronic materials and their applications have been the focus of an increasing tendency of scientists, especially in the field of physics and chemistry. The fact that the structures of organic molecules can be varied easily and the properties of the organic material can be altered directly depending on this change is the main reason for this increasing interest. A new window was opened with the demonstration that the performance of organic materials could be used in the field of optoelectronics, despite the fact that silicon and gallium remain behind arsenic-based materials. It is now known that organic thin films can be used in many applications. These include organic light emitting devices (OLED), organic thin film transistors (OFET), and low cost and effective solar cells (organic solar light cells).
Generally, two groups are used in the production of electronic and optoelectronic devices: small organic molecules and polymers. The main problem in the preparation of such materials is the design of new high performance optical and electronic devices, with a good understanding of the electronic structure of the organic material. The slightest changes in the structure of the organic molecule can change the property of the molecule to a great extent. Today, changing the properties of electronic and optoelectronic materials by making changes in the structure of organic molecules at the molecular level is extremely difficult and important issue. Organic materials based on thiophene are at the top of the list of molecules with promising molecular properties, because their functional properties can be changed by coarse and fine tuning, and are studied by many research groups.
The first active cell used in solar cell applications from organic materials was a silicone-based silk with a 6% yield in 1954. This cell is based on the principle that the addition of silicon arsenic produces negatively charged silicon (n-dope). Today, the yield of silicon-based solar batteries is around 25%.
The use of organic materials in the production of solar cells was aimed at lowering the cost and producing large-scale production, and these researches gained momentum with the finding of pi-conjugated polymers by Shirakawa, MacDiarmid and Heeger in 1977. Inorganic semiconductors generate free electrons and voids (hole, plus charge) by illumination at room temperature, while organic semiconductors absorb light and form a tightly coupled plus minus charge pair called "exciton". Organic materials have a strong "Coulombic" interaction between the electron and the hole due to their low dielectric constant. At the beginning of the research, it is seen that these materials show conversion performances around 13% despite the fact that the first organic solar batteries have a conversion rate as low as 0.3%. Organic solar cells are lighter, more flexible, and less costly than inorganic ones, providing great advantages in the application of such materials in order to be applied to larger areas. In this regard, great efforts are being made to design and synthesize new organic molecules for organic solar cell applications. Among the important reasons for these efforts are the functionalization of organic materials in various forms, so that the optical, electrochemical, solubility, morphological and electrical properties can be finely adjusted.
The aim of this thesis is to examine the preparation and characterization of cyano thienothiophene derived molecules as both triphenylamine and boron containing materials which will play a role in the organic electronics and optoelectronics field. Preparation of these materials is closely related to synthesis chemistry and polymer chemistry. In this respect, the development of the scope of the project as an acceptor group in organic molecules containing non-polymeric and donor-acceptor (DA) units, which can be used in the application of tubes, solar cells, and the use of thienothiophene (TT) derivatives developed by our group as a group of donors with high fluorescence effect for OLED studies. Thus, the material chemistry will gain new organic structures derived from TT in the donor acceptor model.
•	Synthesis of 4-[2-(Thiophen-3-ylsulfanyl)-acetyl]-benzonitrile (1):To a solution of 3-bromothiophene (3 g, 18.40 mmole) in dry diethyl ether, n-butyllithium (8.1 mL, 27 mmol, 2.5 M) was added dropwise at -78 oC, under nitrogen atmosphere. After stirring for one hour, elemental sulfur (S8) (0.65g , 20.24 mmole) was added and the mixture was further stirred for one hour. Then, the temperature was brought to 0 oC and 4-(2-bromo-acetyl)-benzonitrile (4.53g , 20.24 mmole) was introduced portion wise into the mixture. Stirring was continued for overnight and the reaction was quenched with water. The solution was extracted with dichlormethane for 3 times and the organic layer was washed with NaHCO3 (10%) and water. The organic layer was dried over Na2SO4, filtered and the solvent was evaporated under reduced pressure. The crude product was purified by flash column chromatography eluting with hexane:CH2Cl2 (3:1) to give the title compound as white powder (4.02 g, 84%).
•	Synthesis of 4-thieno[3,2-b]thiophen-3-yl-benzonitrile (2) :To a solution of polyphosphoric acid (PPA) (2.5 g, 23 mmol) in chlorobenzene (5 ml) at 135 oC was added 1 (0.6 g, 2.3 mmol) dissolved in chlorobenzene (10 mL) drop wisely. The reaction was heated at this temperature for 6-7 h, after which the mixture was extracted with CH2Cl2, sodium bicarbonate (30% solution) and with water. The organic layer was dried over Na2SO4, filtered and the solvent was evaporated under reduced pressure. The residue was purified by column chromatography eluting with hexane:CH2Cl2 (4:1) to obtain the title compound 2 (0.39 g, 69%).
•	Synthesis of 4-(2-Bromo-thieno[3,2-b]thiophen-3-yl)-benzonitrile (3):To a solution of 2 (0.2 g, 0.83 mmol) dissolved in DMF (4 ml) was added NBS (0.147 g, 0.83 mmol)  at -10 °C in dark. After stirring for 8 h at the same temperature, the mixture was poured into water (50 mL) and the precipitate was filtrated and purified by column chromatography eluting with CH2Cl2:hexane (1:3) to obtain the titled compound 3 (0.22 g, 83%).
•	Synthesis of 4-(2,5-Dibromo-thieno[3,2-b]thiophen-3-yl)-benzonitrile (4):To a solution of 2 (200 mg, 0.83 mmol) dissolved in DMF (6 mL) was added NBS (295 mg, 0.166 mmol)  at -10 °C in dark. After stirring for 8 h at the same temperature, the mixture was poured into water (50 mL) and the precipitate was filtrated and purified by column chromatography eluting with CH2Cl2:hexane (1:3) to obtain the titled compound 4 (0.26 g, 78%).
•	Synthesis of 4-[2-(4-Diphenylamino-phenyl)-thieno[3,2-b]thiophen-3-yl]-benzonitrile (9) :To the mixture of 3 (200 mg, 0.501 mmol) and 6 (279 mg, 0.750 mmol) dissolved in THF (25 mL) and degassed for 10 minutes with N2 was added K2CO3 (2.5 mL, 2 M) and Pd(PPh3)4 (0.002505 mmol) . The mixture was then saturated with N2 and the sealed reaction flask was stirred at 75 oC for 48 h, after which the crude product was filtered through celite, extracted with sodium carbonate, dried over sodium sulfate, filtered and the solvent was evaporated under reduced pressure. The crude product was purified by column chromatography eluting with n-hexane: CH2Cl2 (3:1) to obtain the title compound 9 (227 mg, 75%) as a yellow powder, mp 151-152 oC.
•	Synthesis of 4-(2-(4-(1,2,2-triphenylvinyl)phenyl)thieno[3,2-b]thiophen-3-yl)benzonitrile (11):To the mixture of 3 (150 mg, 0.262 mmol) and 10 (215 mg, 0.47 mmol) dissolved in THF (25 mL) and degassed for 10 minutes with N2 was added K2CO3 (2.5 mL, 2 M) and Pd(PPh3)4 (0.002505 mmol). The mixture was then saturated with N2 and the sealed reaction flask was stirred at 75 oC for 48 h, after which the crude product was filtered through celite, extracted with sodium carbonate, dried over sodium sulfate, filtered and the solvent was evaporated under reduced pressure. The crude product was purified by column chromatography eluting with n-hexane: CH2Cl2 (3:1) to obtain the title compound 13 (175 mg, 65%) as a yellow powder, mp 209-211°C.