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İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Anabilim Dalı

Alkil zincirleri ile sübstitüe asimetrik ftalosiyanin sentezi

Synthesis of alkyl chain substituded unsymmetrical phthalocyanines

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Özet:

Tetrapirol türevleri olarak gruplandırabileceğimiz porfirinler, ftalosiyaninler, tetrabenzo porfirinler ve porfirazinler son yıllarda hem temel bilim, hem de uygulamalı çalışmalar için üzerinde önemle durulan konulardan birini oluşturmaktadır. Tetrapirol makrohalkalarının iki önemli sınıfı olan porfirin (P) ve ftalosiyaninler (Pc), temelde birbirinden farklıdırlar, porfirinler porfin molekülünden oluşurlar. Ftalosiyaninler ise porfirinlerin yapısal tetraazatetrabenzo analoglarıdır. Ftalosiyaninler, porfirin iskeletindeki CH gruplarının yerine pirol halkalarının birbirlerine azot atomları ile bağlandığı porfirazin (Pz) türü bir merkeze sahiptirler. Porfirinler ya moleküler sistemlerde doğal olarak bulunmakta ya da orjinal sentetik ürünlerdir, ftalosiyaninler ise laboratuar çalışmalarından elde edilen tamamen sentetik maddelerdir. Bu gruptan ftalosiyaninlerin üzerindeki 2-boyutlu ? -elektron delokalizasyonu, endüstriden (katalizörler, fotoiletkenler) tıbba (fotodinamik terapi, PDT) kadar pek çok farklı uygulamalarıyla sonuçlanan, nadir fiziki özelliklerinin büyük miktarda artışına sebep olmaktadır. Bu yüzden ftalosiyaninler, olağanüstü optik ve elektriksel davranışlar gösteren kimyasal ve termal olarak dayanıklı bileşiklerdir. Son yıllarda, periferal pozisyondaki sübstitüe grupların farklı olmalarından dolayı bu şekilde adlandırılan asimetrik veya düşük simetrili ftalosiyaninlerin non-lineer optik, fotodinamik terapi gibi alanlarda kullanımı bu konuda yoğun araştırmalara sebep olmaktadır.Ftalosiyaninler, şiddetli ??? * bantları ile beraber düzlemsel heteroaromatik ? -konjuge sisteminden dolayı genellikle mavi-yeşil renktedirler. Bu nedenle boya ve pigment olarak yaygın bir şekilde kullanılmaktadırlar. Ftalosiyaninlerin pek çok uygulamaları, onların karakteristik ? -konjugasyonlarından kaynaklanmaktadır. Uygulama alanlarındaki spesifiklik, Pc halkasının modifikasyonu ile, merkezdeki metalin veya ligandların değiştirilmesi ile arttırılabilmektedir.Simetrik sübstitüe ftalosiyaninlerin hazırlanması için pek çok yöntem keşfedilmesine rağmen, asimetrik ftalosiyaninlerin sentezlenmesinde çok daha az sayıda yöntem uygulanabilmektedir. Bu yöntemler sentezi hedeflenen ürünün türüne göre de farklılık göstermektedir. Farklı iki tür sübstitüent içeren A3B tipi asimetrik ftalosiyanin sentezi için ise uygulanabilirliği en fazla olan yöntem bu sübstitüentleri barındıran başlangıç maddelerinin siklotetramerizasyonudur. Bu yöntemdeki en önemli problem, hedeflenen ftalosiyaninlerin tamamen benzer fiziksel ve kimyasal özellikler gösteren izomer karışımından ayrılmasındaki zorluktur. Başka bir deyişle, istatistiksel kondenzasyon yöntemi hedef Pc için seçimli bir sentez yöntemi değildir. Buna karşın, başlangıç maddelerinin oransal değişimi ile istenen asimetrik türün verimi arttırılabilmektedir.Bu çalışma iki aşamadan oluşmaktadır. Birinci aşamasında üç benzen ünitesi üzerinde periferal hekziltiyo sübstitüentleri ile dördüncü benzende bir hidroksietiltia grubunun bulunduğu asimetrik metalsiz ftalosiyaninler sentezlenmiş ve ikinci aşamasında da metalsiz ftalosiyaninler farklı metal tuzları ile reaksiyona sokularak metalli ftalosiyaninlerin sentezi gerçekleştirilmiştir.Birinci aşamada, 4,5- dihekziltiyo ftalonitril (1) ve 4-(2-hidroksietiltia)ftalonitril (2) başlangıç bileşenleri olarak seçilip Li metali varlığında -pentanol içerisinde öncelikle Li2Pc sentezi gerçekleştirilmiş, daha sonra asetik asit ile asitlendirilerek metalsiz Pc'ye geçilmiştir. Sentez için istatistiksel kondenzasyon yöntemi tercih edilmiş ve 4,5- dihekziltiyo ftalonitril (1) ile 4-(2-hidroksietiltia)ftalonitril (2)' in 3:1 oranında reaksiyona girmesi sağlanmıştır.Yüksek sıcaklıkta ve kapalı bir tüp içerisinde gerçekleştirilen reaksiyon sonunda farklı tipte simetrik ve asimetrik izomer karışımı elde edilmiştir. A3B yapısındaki 3 nolu asimetrik Pc farklı elüent sistemlerinin kullanıldığı silikajel dolgulu kolon kromatografisi ile saflaştırılmıştır.Çalışmanın ikinci aşamasında ise, saf olarak elde edilen 3 nolu bileşiğin pentanol içerisinde farklı metal tuzları (Zn(CH3COO)2, CoCl2) ile kondenzasyonundan metalli asimetrik ftalosiyaninler (4, 5) sentezlenmiştir. Son olarak da 3, 4, 5 bileşiklerinin yapısı elementel analiz, UV-vis, FT-IR, 1H NMR ve kütle spektrumu teknikleri kullanılarak karakterize edilmiştir.

Summary:

Porphyrins, phthalocyanines, tetrabenzoporphyrins and porphyrazines are tetrapyrrole derivatives receive extensive attention for both theoretical studies and applications in advanced materials science. Tetrapyrrole macrocycles are either original synthetic products or naturally occurring molecular systems, whereas porphyrazines and phthalocyanines derive exclusively from synthetic laboratory work. Phthalocyanines are distinguished from porphyrazines by the presence of benzo rings fused to the pyrrole rings in the former. Phthalocyanines (Pcs), as the most studied and best-known class of porphyrazines, have attracted considerable attention and present an important and active frontier, due to their interesting and useful biological, electronic, optical, catalytic, and structural properties. Due to extensive delocalized two-dimensional ?-system of phthalocyanines gives them rare physical properties to afford usability in differnet applications from industry (catalyst, photoconductor) to medicine (photodynamic therapy). Therefore, phthalocyanines which display tremendous optical and electrical properties have great stability. Since then, their outstanding and tailorable properties such as liquid crystallinity, generation of singlet oxygen and redox properties have enhanced their use as efficient agents in several high technology applications including: photodynamic therapy a technique for which phthalocyanines are currently the most promising class of compounds for photodynamic antimicrobial chemotherapy as sensors including biosensors for non-linear optical applications dye sensitised photovoltaic production semiconductor materials oxidation or reduction catalysts and photocatalysts among others. Their combination with nanomaterials (quantum dots, nanotubes, liposomes, dendrimers) may efficiently enhance the desired properties. In recent years, unsymmetrical phthalocyanines which contain different groups on the peripheral positions are studied for applications in nonlinear optics, photodynamic therapy intensively. More recently, particular attention has been paid to the development of unsymmetrical phthalocyanines. This is because such chromophores possess a number of unique physicochemical properties and improved organization capabilities, which render these compounds valuable applications in materials science, in particular in photodynamic anticancer therapy and non-linear optics for optical limiting applications and optical signal detection techniques.The intrinsic structure of these compounds makes them, when unsubstituted, insoluble in nearly all the solvents. However appropriate substitution pattern helps to overcome this problem. Indeed, the flexible points for a chemist aiming at synthesizing soluble phthalocyanines are the substitution pattern (macrocyclic and/oraxial) as well as the choice of the metal. The introduction of one or two nitrogen atoms on the isoindole subunits (the corresponding tetrapyridinoporphyrazine and pyrazinoporphyrazine derivatives being commonly designated as azaphthalocyaninesis another point allowing for the tailoring of properties.Water-solubility is a quest for many chemists in various fields, as several of the current applications of phthalocyanines are of biological interest and/or require environment friendliness, necessitating water-solubility in various concentration, pH, etc. ranges. This is the case of biological and medical applications such as photodynamic therapy. Another very important application of water-soluble phthalocyanines is the catalysis of reactions in aqueous media, the main one being the degradation of pollutants. Catalysis of reactions in aqueous media is currently becoming of major interest. Thus, when designing a phthalocyanine on demand for a specific application, or to get a precisely targeted property, its water-solubility may be a requirement.Phthalocyanines are generally blue-green in color due to the intense ??? * bands associated with the planar heteroaromatic ? -conjugation system. As a result, phthalocyanines have been used extensively in dyes and pigments. Most of the applications of phthalocyanines stem from their characteristic ? -conjugation systems. Specificity in the applications of phthalocyanines can be introduced by modification of the phthalocyanine ring or by changes in the central metal or ligands.The symmetry of radially symmetric phthalocyanines with AAAA structures can be lowered by introducing structural modifications, which result in a folding of the ?-system of the ligand. For example, slight deviations from planarity are often observed in X-ray structures of metal complexes when the central metal ion does not fit into the central cavity. Another potential source of nonplanarity is steric hindrance between peripheral substituents at the ? and ß positions.Low symmetry phthalocyanine derivatives allow for the fine-tuning of many physical properties responsible for enhancing technological applications of phthalocyanines and have thus become of increasing interest in fields such as non-linear optics, photodynamic therapy (PDT) of cancer and and in the development of ordered phthalocyanine Langmuir?Blodgett thin films.Despite the variety of synthetic routes developed to prepare symmetrically substituted phthalocyanines, relatively few methods can be applied for preparing unsymmetrical ones. Synthesis via statistical condensation method is the most widely used strategy to prepare A3B-type Pcs, the Pcs bearing three identical (A) and one different (B) isoindole subunits, and it usually affords a mixture of six compounds. Commonly, 3:1 to 9:1 ratios between A and B are employed, which favor the formation of the unsymmetrical Pcs but sometimes 10:1 and even higher ratios (i.e., 40:1) were also used, due to the different effects of substituents. Although this method has been widely used for the synthesis of A3B-type Pcs, it is often laborious, due to difficulty in separating similar chemical structures. Synthesis via ring expansion of subphthalocyanine is the other method to prepare unsymmetrical phthalocyanines. Subphthalocyanines (SubPcs) are non-planar coned-shaped (saddle-shaped) aromatic molecules with 14? electrons and a trigonal geometry. One of the most important applications of SubPcs is to form the asymmetrically substituted phthalocyanine by ring expansion employing substituted phthalonitriles or diiminoisoindolines Good yields were obtained when the SubPc was treated with phthalonitriles or diiminoisoindolines in the presence of a strong base, such as DBU, and a metal salt. However, its more widespread application was limited, due to its dependence on the solubility and reactivity of the reactants and the experimental conditions. Thus, there is still a lot of work to do in the search for favorable reaction parameters and to gain a better understanding of the mechanism of the ring-expansion approach. In 1982, a polymerization strategy approach (solid-phase synthesis) was developed for the selective preparation of A3B type Pcs. In this strategy, the reaction involves the introduction of the substituted phthalonitrile or diiminoisoindoline into an insoluble polymer, and then this starting polymer reacts with an excess of another different substituted phthalonitrile or diiminoisoindoline, affording the desired unsymmetrical A3B-type Pc after liberation from the polymer . However, this method has not seen widespread application and only a few examples have been reported to date.This work come into being two parts; in the first part, we report on the synthesis and characterisation of unsymmetrical H2Pc which carry two peripheral hexylthio substituents on each of three of the benzenoid groups while the fourth one carries two phenylethynyl groups. In the second part, H2Pc converts to metallo phthalocyanines by treating with metal salts.Firstly, a mixture of 4,5-di(hexylthio)phthalonitrile (1), 4-(2-hydroxyethylthio) phthalonitrile (2) and lithium metal in pentanol was heated and stirred to synthesis of Li2Pc. The reaction mass was then treated with acetic acid and the Li2Pc formed was converted into H2Pc. Statistical reaction of 4,5-di(hexylthio)phthalonitrile (1) and 4-(2-hydroxyethylthio)phthalonitrile (2) in a 3:1 ratio was preffered to synthesis of this compound.Different types of symmetric and unsymmetric isomer mixture was obtained by heating phthalonitrile derivatives in pentanol under N2 atmosphere in a sealed tube. A3B type (3) unsymmetrical Pc was gained by flash column chromatography with SiO2 and gradient elution of CH2Cl2:CH3OH.In the second part of the study, metallo phthalocyanines were synthesized. New Zn (II) (4), Co (II) (5)phthalocyanines were synthesized by reaction with divalent metal salts (Zn(CH3COO)2 or CoCl2). In the final part, the structures of obtain compounds were characterized by using UV-vis, FT-IR, 1H NMR and mass techniques.