Karbazol, pirol substituye asimetrik ftalosiyaninlerin sentezi, elektrokimyasal polimerizasyonu ve karakterizasyonu

Abstract

Ftalosiyaninler termal kararlılıkları, kimyasal dirençleri, elektriksel ve optiksel özelliklerinden dolayı hem teorik alanda hem de uygulama alanında büyük öneme sahip heterosiklik sistemlerdir. 1907 yılında tesadüf eseri keşfedilen bu bileşiklerin yapısı ise daha sonraki yıllarda aydınlatılabilmiştir. 18 π elektronlu aromatik bir yapıya sahip olan bu bileşikler sahip oldukları 1.35 Ao halka boşluğuna çok çeşitli metalleri alabilmektedir. Metallerin çeşitliliği sonucunda ortaya çıkan bileşiklerin de özellikleri çeşitlenmektedir. Pc'ler HNO3 ve KMnO4 gibi kuvvetli oksiteyiciler dışında asitlerle reaksiyon vermezken bu bileşiklerle etkileşimi sonucu ise başlangıç bileşiği olan ftalimide dönüşürler. Termal olarak da çok kararlı olan bu bileşiklerin erime noktaları yoktur. Pc bileşiklerininin UV-Vis spektrumunda verdikleri karakteristik pikleri sayesinde kolayca karakterizasyonu gerçekleştirilebilmektedir. Spektrumda 600-720 nm arasında şiddetli Q-bandı, 300-400 nm aralığında ise daha az şiddette B-bandı vermektedirler. Kullanım alanları çok geniş olan ftalosiyanin bileşiklerinin bu alanlarda kısıtlamaya yol açan özellikleri ise organik çözücülerde çözünürlüklerinin çok düşük olmasıdır. Bu sorunu aşmak için ise ftalosiyanin bileşiklerinin periferal ve non-periferal konumlaırna çeşitli sübsitüentler eklenmektedir. Bu sübstitüentlerin hacimli gruplardan seçilmesi sonucu agregasyon da önlenmiş olmaktadır. Sübstitüentlerinin aynı ya da farklı olmasına göre simetrik ya da asimetrik ftalosiyaninler olarak adlandırılmaktadırlar. Simetrik ftalosiyaninler, bütün sübstitüentleri aynı olup sentezi ve saflaştırılması daha kolay olan bileşiklerdir. Asimetrik ftalosiyaninler ise saflaştırılması kompleks kromatografik yöntemler içerek bileşik türüdür. Asimetrik ftalosiyaninlerin sentezi için üç farklı yöntem bulunmaktadır: İstatistiksel karışım yöntemi, subftalosiyanin yöntemi ve polimer destekli sentez yöntemi. Bunlardan en sık kullanılan yöntem ise istatistiksel karışım yöntemidir. Ftalosiyaninlerin elektrokimyasal özellikleri, Pc'nin bir ligand oluşundan kaynaklı merkezinde bulundurduğu metal katyonunun ve üzerindeki 18π-elektron sistemi arasında gerçekleşen etkileşimlerden kaynaklanmaktadır. Ftalosiyaninin indirgenip yükseltgenmesinin yanı sıra merkezde bulunan metal katyonu da indirgenip yükseltgenebilir. Elektrokimyasal analiz yöntemlerinden birisi olan dönüşümlü voltametri tekniği ftalosiyaninlerin komplekslerinin, merkezlerindeki metallerinde veya kendi üzerlerindeki yapıdan kaynaklı elektrokimyasal olayların incelenmesini mümkün kılar. Yapının üzerine eklenmiş sübstitüentlerin de bu yapıya etkisinin analizi mümkündür.Bu çalışmada 2,3,9,10,16,17,23,24 – oktakis (hekziltiyo) ftalosiyaninato kobalt (II) sentezi ve pirol ve karbazol sübstitüe 2,3,9,10,16,17 – hekzakis (hekziltiyo) – 23 (24) -(4-(1H-pirol-1-il)fenoksi) ftalosiyaninato kobalt (II) ve 2,3,9,10,16,17 – hekzakis (hekziltiyo) – 23 (24) –(9H-karbazol-9- etoksi) ftalosiyaninato kobalt (II) asimetrik ftalosiyaninlerin ve bunların başlangıç bileşiklerinin sentezi gerçekleştirilmiştirSentezlenen bileşiklerin karakterizasyonları IR, UV-Vis, H-NMR ve kütle spektroskopileri ile yapılmıştır.İkinci kısımda ise karbazol ve pirol sübstitüe asimetrik ftalosiyaninlerinin ve bu bileşikten elektropolimerizasyonla elde edilen polimer yapılarının elektrokarakterizasyonları gerçekleştirilmiştir.

Phthalocyanines are heterocyclic molecules that show great thermal stability, chemical resistance, electrical and optical properties. That properties make phthalocyanines feasible for applications of electirical and optical fields. Phthalocyanines discovered in 1907 by coincidence. However, its molecular structure was brightened years later. It is a strong field ligand which has an aromatic 18 π electron system at the skelleton of the structure. Inner free space of 1.35 Ao makes phthalocyanine accept different kinds of metals to its center to create a complex. As the metal changes, the chemical behaviours of the phthalocyanine change as well.Phthalocyanines generally do not react with acids, only nitric acid, potassium permanganate or that kind of acids may able to oxidize phthalocyanine to its starting reactant, phthalmide. That chemical resistance is a valuable benefit for phtalocyanines, furthermore phthalocyanines have very high thermal stability too. As a result of that thermal stability, there is no melting point observed for phthalocyanines.Phthalocyanine complexes have characteristic bands on UV-Vis spectrums which makes it possible, even easy to distinguish weather it is a phthalocyanine or not. In the spectrum, a strong Q-band around 600-720 nm and a less strong B-band around 300-400 nm can be observed. The most preferred method for the synthesis of metalophthalocyanine is by boiling the commonly used starting material, phthalonitrile, with a suitable high-boiling solvent in the presence of a template-forming metal ion. Alkyl chains, simple functional groups such as amine, ether and thiol, as well as substituents such as crown ether, dendrimer and ferrocene, can also be attached to phthalocyanines. With the addition of these groups, the uses of phthalocyanines are diversified.The method of cyclotetramerization of the substituted starting materials with metal is generally used to obtain substituted phthalocyanines.Phthalocyanines find theirselves wide usage areas. However it cannot be dissolved in most of the organic solvents. It diminishes the feasibility of the phthalocyanine. To be able to overcome that disadvantage, different kinds of substituents are being attrached to the skelleton of phthalocyanine, either periferal or non-periferal positions of it. By choosing that substituents as considerably large groups, it can be protect the skelleton of the phthalocyanine to be aggregerated. While modifying the phthalocyanine, it is not necessary to stick only one type of substituent to a skelleton four times. Substituent groups can differ on one phthalocyanine structure. By the symmetry of the substituents, they were named as symmetric or asymmetric phthalocyanines. Symmetric phthalocyanines are containing only one type of substituent, which is generally bonded to main structure four times by a coovalent bond each. They are easy to purify. However, asymmetric phthalocyanines may require advanced chromatographic methods to be able to be purified. There are three different methods for the synthesis of asymmetric phthalocyanines: Statistical condensation method, subftalocyanine method and polymer supported synthesis method. The most commonly used method is the statistical condensation method.In the statistical condensation method, although the synthesis step is easy, it is difficult to separate the targeted compound from the product mixture obtained. Various chromatographic methods are used for separation. In the subphthalocyanine method, although it is very easy to purify the targeted asymmetric phthalocyanine structure, it is difficult to synthesize the subphthalocyanine structure. In the polymeric assisted synthesis method, which is the last synthesis method, bonding and breaking the polymeric structure to the compound complicates the process.Phthalocyanines have a wide range of uses. Because of their colors, they are mostly used as dyestuff. As a result of various studies, some metal phthalocyanine derivatives have been shown to show antibacterial properties against various bacterial species. The antibacterial properties of phthalocyanines differ according to the metal ion and the substituents. Phthalocyanines and metal complexes can be also used in various sensor devices because their properties can be modified according to the ambient conditions. Furthermore, phthalocyanine compounds having redox active metal ions are used as catalysts in many reactions.Electrochemistry is actively used industrially for the synthesis of 1A metals such as metallic sodium, potassium, and 2A metals such as calcium magnesium, for the coating of plates with transition metals to use in the basic reaction types of chemistry, reductions, oxidations or other organic synthesis steps. Coating has been applied in the industry with high efficiency and success for many years. The science of electrochemistry, which is formed on these foundations, is also used in battery development fields today. Various methods in electrochemistry are also used for analytical purposes. These methods can be classified as electrochemical analyzes. Electrochemical analysis techniques can be simply divided into dynamic and static methods. Systems where net current is zero are called static systems, and methods where net current changes are called dynamic techniques. Voltammetry is a technique based on voltage measurement. It is one of the measurement techniques that find the most usage area among electroanalytical methods. This technique works by measuring the change in current value in the system based on the changed voltage.Phthalocyanines electrochemical features caused from the interaction between the 18 π electron system of the phtalocyanine and the metal which is bonded to it. It is possible to reduce or oxidize the phthalocyanine, but it is also possible to oxidize or reduce the metal too. To be able to observe this electrochemical features of phthalocyanine cyclic voltammetry is used. Ths technique makes it possible to analyze the interactions between metal and the phthalocyanine. Also effect of the substituents on phthalocyanine can be observed by this technique.At the beginning of the study, the synthesis of 4,5-di (hexylthio) phthalonitrile, 4- (4-pyrrol-1-yl) phenoxy phthalonitrile and 4– [9H-carbazol-9-ethoxy-] phthalonitrile was performed. The synthesis of asymmetric phthalocyanines was then carried out using these starting compounds. Following that, syntehis of 2,3,9,10,16,17,23,24 – octakis (hexylthio) phthalocyaninato cobalt (II) and pyrole and carbazole substitued 2,3,9,10,16,17 – hexakis (hexyilthio) – 23(24) - (4-(1H-pyrole-1-yl)phenoxi) phthalocyaninato cobalt (II) and 2,3,9,10,16,17 – hexakis (hexyilthio) – 23(24) – (9H-carbazole-9-etoxi) phthalocyaninato cobalt (II) were performed.Characterisation of these compounds was performed by IR, UV-Vis, H-NMR and mass spectroscopies. At the second part of this thesis, carbazol and pyrole substitued phthalocyanines, and their electropolymerized polymer structures were characterized by electrochemistry.