Supramolecular structures based on porphyrazines

Abstract

Porphyrins, phthalocyanines, tetrabenzo porphyrins and porphyrazines which are tetrapyrrole derivatives. Because of both theoretical studies and applications in advanced materials science, tetrapyrrole derivatives receive extensive attention. Porphyrins are important not only from biological aspect but also for coordination chemistry as catalysis and material science. Phthalocyanines which are used in electro-photography, optic data collection, gas sensor, liquid crystal, laser technology and the photodynamic therapy of tumors as well as their classical fields as pigments and dyes, are completely synthetic materials. Porphyrazines that have functionalized groups at pheripheral positions have the potential to exhibit novel optical, magnetic and electronic properties. They also maintain some additional features superior to the values met in related materials. Additions of the transition metal ion in the inner core of a porphyrazine offer new ways to induce, modify and control molecular properties. The starting point for a novel porphyrazine structure with eight (1- naphthyl) groups bound to the periphery is 1,2-bi ( naphthyl )dinitrile which was obtained by oxidative coupling of 1-naphthylacetonitrile in the presence of I2. The solid product was obtained in a yield of 21%. It was a mixture of maleo-and fumaro-nitriles and the latter was present in higher ratio as expected from the presence of bulky naphthyl substituents. The mixture of maleo-and fumaro-nitrile reluctance to turn into porphyrazine under the usual conditions (i.e. Mg(OR)2 in refluxing propanol or butanol) points out the lower ratio of the maleonitrile component. This problem was solved by activation of the fumaronitrile derivative to the corresponding pyrroline derivative 3,4-(1-naphthyl)pyrroline-2,5- diimine which cyclizes quite easily to porphyrazine at reflux temperature of propanol or butanol. Conversion of 3,4-(1-naphthyl)pyrroline-2,5-diimine into porphyrazine was achieved by the template effect of magnesium butanolate. Cyclotetramerization gave green-colored octakis(1-naphthyl) porphyrazinato magnesium in yield (70%). It is soluble in chloroform, dichloromethane and acetone, but insoluble in apolar hydrocarbon solvents such as n-hexane. Intensive research interest on peripherally functionalized porphyra-zines during the last decade has shown that these tetrapyrrol derivatives should be considered in many respects as an alternative to phthalocyanines. The porphyrazine macrocycles afford a skilful platform to build up detailed molecular superstructures and this property coupled with a full and well-improved synthetic chemistry has surpassed to the synthesis of different catalytically essential metallo porphyrazines and original model compounds of various functions. In this study magnesium porphyrazinate substituted with eight (1- naphthyl) groups on the peripheral positions has been synthesized by cyclotetramerization of 3, 4-(1- naphthyl)pyrroline-2,5-diimine in the presence of magnesium butanolate. Its demetallation by treatment with trifluoroacetic acid result with a partially oxidized product, namely, octakis(1-naphthyl)-2- seco-porphyrazine-2,3-dione. Further reaction of this product with copper(II) acetate, zinc (II) acetate and cobalt (II) acetate led to the metallo derivatives, [octakis (1-naphthyl)-2-seco-2, 3-dioxoporphyrazinato]M (II) (M= Cu, Zn, Co). These new compounds have been characterized by elemental analysis, together with FT-IR, 1H NMR, UV-Vis and mass spectral data. Since naphthyl groups are comparable with dimethylamino groups as electron donors to 18-π electron system of the inner core , in the demetallation reaction, relatively strong acids (e.g. trifluoroacetic acid) inhibits the electron donating strength of the dimethylamino groups much more than naphthyls. Sterical tension due to the presence of eight bulky naphthalene units around the core might be another reason for the cleavage of one of pyrrol rings. These should be taken together with the oxidation resulting from singlet oxygen cycloaddition reactions as described in early works. The presence of an electron donating group on the periphery causes a bathochromic shift on Q bands. UV-Vis spectra of porphyrazines (1, 3-5 in CHCl3) prepared in the present work exhibited intense single Q band absorption of the π→π* transitions around 632-644 nm and B bands in the UV region around 340-348 nm.For metal-free derivative (2), Q band is split into two peaks at 620 and 676 nm as a consequence of the lowering of the symmetry of porphyrazine core. In conclusion, new seco-porphyrazines with eight naphthyl groups have been described; Together with their high electron donating property, steric requirements of the eight bulky naphthyl substituents can be the reasons leading to oxidized seco-porphyrazines.

Özet

Porfirinler, ftalosiyaninler, tetrabenzo-porfirinler ve porfirazinler tetrapirol türevleridir. Bu yapılar, son yıllarda hem temel bilim hem de uygulamalı çalışmalar için üzerinde önemle durulan konulardan birini oluşturmaktadır. Porfirinler sadece biyoloji açısından önem taşımakla kalmayıp zengin koordinasyon kimyası, kataliz ve malzeme bilimindeki uygulamaları ile de ilgi çekmektedir. Ftalosiyaninler, tamamen sentetik ürünlerdir. Bunların boyar madde ve pigment olarak değerlendirilmesi yanında enerji dönüşümü, elektrofotografi, optik veri toplanması, gaz sensör, sıvı kristal, lazer teknolojisi için kızılötesi boyar madde ve tek boyutlu metaller gibi pek çok uygulaması bulunmaktadır. Fonksiyonel substitüent taşıyan porfirazinler üzerinde yoğun çalışmalar yapılmaktadır. Bu tetrapirol türevlerinin birçok açıdan fitalosiyaninlere alternatif olabileceği düşünülmektedir. Porfirazinlerin makrohalkaları oldukça işlevsel makro moleküllerin oluşturulmasını sağlar. Bu tür makrohalkalı bileşikler, biyolojik etkileri nedeniyle, oldukça önemli bileşiklerdir. Halka üyesi olarak azot, kükürt ve oksijen gibi atomları içeren heterohalkalı bileşikler hem endüstrinin çeşitli alanlarında hem de tıpta yaygın bir şekilde kullanılmaktadırlar. Bu çalışmada peripheral konumlarında sekiz adet naftil grubu bulunan magnezyum forfirazin 3,4-(1-naftil)pirolin-2,5-diimin’nin magnezyum butanolat mevcudiyetinde halkalaşması sonucu elde edilmiştir. Bu madde trifloroasetik asit ile işleme tabi tuturak metalsizleştirilmiştir. İşlem sonucunda kısmi oksitlenmiş bir bileşik olan oktakis(1-naftil)-2-seko-porfirazin-2,3-dion’un oluştuğu belirlenmiştir. Metalsiz seko-porfirazinin bakır(II) asetat, çinko(II) asetat ve kobalt(II) asetat ile reaksiyonundan metalli türevleri olan [oktakis(1-naftil)-2-seko-2,3-dioksopor-firazinat]M(II) bileşikleri elde edilmiştir (M=Cu, Zn, Co). Oluşturulan yeni bileşikler FT-IR, 1H NMR, UV-Vis ve kütle spektrumları alınarak elementel analizleri yapılarak karakterize edilmiştir.