Yeni fluoresans organik materyallerin sentezi: Antrasen-flouren hibrit oligomerleri
Synthesis of new fluorescent organic materials: Anthracene-fluorene hybrid oligomers
Yazar: NURGÜL AKCEBE
Danışman: YRD. DOÇ. DR. BARIŞ YÜCEL
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Ana Bilim Dalı
Derece: Yüksek Lisans, 2014
Konu: Kimya = Chemistry

Özet:
Bu çalışmada antrasen ve fluoren türevlerinden oluşan oligomerik yapılar, Suzuki Kenetlenme Reaksiyonu aracılığı ile sentezlenmiştir. Benzosiklobütendion başlangıç maddesinin 2-bromo-7-lityo-9,9-dialkilfluoren türevleri ile -78°C sıcaklıkta reaksiyonundan elde edilen alkol ara ürününün p-ksilen içinde çözülerek, havaya açık ortamda, geri soğutucu altında kaynatılması sonucu brom bağlı indenoantrakinon türevleri elde edilmiştir. İndenoantrakinon türevleri alkinillityum ve fluorenillityum gibi çeşitli gruplar ile 0°C sıcaklıkta reaksiyona sokularak indenoanthrasen türevleri sentezlenmiştir. Suzuki kenetlenme reaksiyonu ile indenoantrasen türevleri ve alkil subsitüe 2,7-dibromo fluoren ya da alkil sübsitüe 2-bromofluoren maddeleri reaksiyona sokulmuş ve oluşan oligomerler ve bu oligomerlerin floresans özellikleri incelenmiştir. Farklı indenoanthrasen türevleri ve alkil grupları takılmış fluoren türevleri kullanılarak dört farklı, yeni oligomer elde edilmiştir. Çeşitli kondisyonlar denenerek en iyi sonuçlar elde edilmeye çalışılmış ve kuvantum verimi, ürün verimi gibi parametrelere bakıldığında bunda başarılı olunduğu görülmüştür.
Asen ve fluoren türevlerinin optoelektronik uygulamalarda kullanılması son yıllarda oldukça yaygınlaşmıştır. Bundaki temel faktörler; organik materyallerin silikon bazlı materyallere kıyasla daha küçük alanlara uygulanabilmesi, yine bu materyallerin sahip olduğu yüksek esneklik, düşük ağırlık ve çeşitli metotlarla organik ve inorganik çözücülerde çözünebilir hale getirilebilmesi gibi özelliklerdir. Bu çalışmada asen ve fluoren türevi materyallerin her birinin sahip olduğu, yüksek konjugasyon, yüksek yük taşıma mobilitesi, yüksek kuvantum verimleri gibi optoelektronik özelliklerin birleştirilerek bahsi geçen özelliklerin verimlerinin arttırılması amaçlanmıştır. Ayrıca moleküllerin uygun pozisyonlarına çeşitli sübsitüentler bağlanarak çözünürlük problemleri de ortadan kaldırılmıştır

Abstract:
The oligomeric structures, which synthesized with anthracene and fluorene derivatives by Suzuki cross-coupling reactions and their fluorescent properties, were investigated. The reaction of benzocyclobutenedione with 2-bromo-7-lithio-dialkylfluorene derivatives at -78ºC gave the alcohol intermediates. These alcohol derivatives were heated at 165ºC during 2 hour in p-xylene at reflux open to the air to oxidate to indenoanthraquinone derivatives. Then, indenoanthraquinone derivatives were reacted with alkynllithiums such as phenyllithium or fluorenyllithium at -78ºC under nitrogen atmosphere to obtain indenoanthracene derivatives. At final step, the brominated indenoanthracene derivatives were reacted with alkylated 2-bromofluorene and alkylated 2,7-dibromofluorene units by Suzuki cross-coupling reaction to furnish highly fluorescent oligomeric structures, which were soluble in organic solvents. Palladium based catalysts are used in Suzuki cross-coupling reaction. The reaction was held 24 hour and under 100ºC in a 25 ml reaction bottle. Different reaction conditions were tested to achieve optimum results. All purification processes like filtration, extraction, column chromatography etc. were applied to take pure substances.
The oligomers that synthesized in this study have a new structural unit formed by participation of a phenyl ring with both chromophoric units (acene and fluorene) and this hybrid unit (indenoanthracene) displays intrinsic properties of parent chromophors in a one form. By this way, it is observed that the proposed acene-fluorene hybrid oligomers exhibited enhanced fluorescence properties (high quantum yields, efficient fluorescence half-life), higher thermal and photo stability. Additionally, these oligomers were soluble in common organic solvents because of alkyl chains on the cyclopentane rings in the main skeleton. Indenoanthracene parts of the oligomers were synthesized by a benzocyclobutenedione-based method. Basically, this method relies on thermal rearrangement of 2-hydroxybenzocyclobutenones to corresponding indenoanthraquinones. Functionalized indenoanthracene units were achieved by reactions of these quinones with organo lithiums (phenylethynyl and fluorenylethynyl lithiums. In addition, alternative approaches to produce desired oligomers were also described. In this study, four new acene-fluorene based oligomers were synthesized with a high efficieny, a good quantum yield and fluorescence half-life properties. The study is involved synthesis of oligomeric structures containing substituted acene and fluorene units by Suzuki cross-coupling reaction. The efficieny and importance of Suzuki-cross coupling reaction is a well-known and awarded fact in reaction chemistry. Effective use of the Suzuki reaction for synthesized acene-fluorene based oligomers is other innovative feature of this study.
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In this work, there was a new structural unit formed by participation of a phenyl ring with both chromophoric units (acene and fluorene) and this hybrid unit displays intrinsic properties of parent chromophores in a one form. By this way, the prepared acene-fluorene hybrid oligomers exhibited enhanced fluorescence properties. Additionally, the alkyl chains that were bonded to main skeleton of molecules overcame solubility problem. Acene and fluorene based materials have been commonly used in optoelectronic technologies since 1950s. Both of these molecules and their derivatives have high electronic properties. The main problem about these type of molecules is solubility. However, by alkylation and acylation in the center part of the molecule, this problem is overcome in the previous studies. Acene and fluorene derivatives constitute an important place as excellent electron transport materials in organic electronic devices such as in organic thin film transistors (OTFTs), organic light emitting diodes (OLEDs) and solar cells. The device applications of these molecule derivatives were experienced in recently years. The main reasons, which is prefered these materials to silicon based ones, are easy application on small areas, high flexibility, low weight, and that can become soluble in organic and inorganic solvents by using some different methods. Nowadays, technology trends to flexible and small devices. So these properties of acenes and fluorene-based molecules have become important.