Please use this identifier to cite or link to this item: http://hdl.handle.net/11527/16323
Title: Çözünür yeni kobalt ve demir porfirazin türevlerinin sentezi
Authors: Gül, Ahmet
Hasanov, Begenç
66377
Kimya
Chemistry
Keywords: Demir
Kobalt
Porfirazinler
Iron
Cobalt
Porphyrazines
Issue Date: 1997
Publisher: Fen Bilimleri Enstitüsü
Institute of Science and Technology
Abstract:  Tetrapirol türevi makrosiklik bileşiklerden porfirinler biyokimyasal önemleri nedeniyle, ftalosiyaninler ise pigment ve boyarmadde olarak ticari kullanımları yanında yüksek teknolojik uygulamalar için gerekli ileri malzemeler olarak yoğun bir şekilde araştırılmaktadır. Sadece meso konumlarında metin (= CH -) grupları yerine aza (- N=) grupları bulundurmaları nedeniyle porfirinlerden farklılık gösteren porfirazinler ile yine benzer yapıdaki tetrabenzoporfirinler üzerinde ise başlangıç maddelerinin elde edilmesindeki güçlük ve reaksiyon şartlarının ağırlığı yüzünden aynı nispette çalışmaya rastlanılmamaktadır. Bu çalışmada çözünür porfirazinler sentez edip, Co ve Fe türevlerini elde ettikten sonra, bu bileşiklerin merkezi metal iyonlarına eksene! olarak bağlanan ligandlar vasıtasıyla monomerik ve oligomerik yapıda yeni bileşiklere geçmek ve elde edilen ürünleri analog yapıdaki ftalosiyaninlerle karşılaştırmak amaçlanmıştır. Sodyum siyanür ve karbon sülfür gibi basit başlangıç maddelerinden çıkarak iki adımda ditiyomaleonitril disodyum tuzu sentezlenmiş, oktilbromür ile alkilleyerek 1,2 - bis (oktiltiyo) - 1,2 - disiyanoetilen elde edilmiştir. Bu bileşikten magnezyum butanolatın template etkisi ile butanol içerisinde oktakis (oktiltiyo) porfirazinato magnezyuma (Mg Pz) geçilmiştir. Metalsiz porfirazin (H2 Pz), toprak alkali Pz türevlerini kuvvetli asilerle ve özellikle trifloroaseik asid ile muamele etmek suretiyle başarılmıştır. H2 Pz'nin 2 - kloroetanol / etanol karışımında kobalt (ÎI) - asetat ile muamele edilmesiyle oktakis (oktiltiyo) porfirazinato kobalt (II) (Co Pz) elde edilmiştir. Co Pz biryandan NaBFLj ile Co (I) türevine indirgendikten sonra, alkil halojenür, asetik anhirid veya dialkil haiojenür ilavesiyle organo kobalt (III) porfirazin bileşiklerine dönüştürülmüş, öte yandan aseton içerisinde KCN mevcudiyetinde hava geçirerek yapılan oksidasyonla monomerik K[Co Pz (CN)2] elde edilmiştir. Bu monomerden su etkisiyle KCN eliminasyonu sağlandığında [Co Pz (CN)]" formülüyle gösterebileceğimiz " şiş kebap " yapısı olarak adlandırılan oligomerik yapıya ulaşılmıştır. H2 Pz ile demir (II) asetatın asetik asiddeki reaksiyonunda bitirme işlemlerinde H Cl çözeltisi kullanıldığı için Fe Pz Ci formülüne uyan trivalent yapı ortaya çıkmıştır. Bu bileşiğin uzun süre piridin ile reaksiyonu monomerik bis (piridin) kompleksi FePz(py)2'yi, bidendat pirazin ile reaksiyonu ise "şiş kebap" yapısında oligomerik [Fe Pz (pyz)]n ürününü vermiştir. Sentezi gerçekleştirilen bileşiklerin yapılan elementel analiz yanında, IR, UV - Görünür Bölge, 1H NMR ve / veya kütle spektrumları yardımıyla aydınlatılmaya çalışılmıştır.
An important group of coordination compounds is that of tetrapyro! derivatives which receive intenest due to both practical and îheoretical point of view. A 16 - membered electron rich conjugaîed pianar macrocyciic core is common in ali these structures. When this main core is composed of four pyrol units bound to öne another through methine (- CH =) bridges, it is cailed porphyrine. Four benzo condensation on each of the pyroi groups result with tetrabenzoporphyrine. Changing methine bridges with aza functions ( =N- ) in porphyrines resuit with porphyrazines (ör tetraazaporphyrines ). The benzo condensed porphyrazines are the weli known phthalocyanines (Fiğ 1). KJ '|! «' n' ş!..-/rY>"-.^VY>- V=N UN-f \=:^ ^_f "J~\ /R) 4 /' /- NÜ N-\ J-Ntl N-/.'-ÇVY-* «--OsÂ^-"1 R' H3 K1 n1 R1 a c MN=( ><)-N r^V^.' ^t^>, H- M-W k-x^/ : v-1^^ N=^y-ü b ö d' Figüre l. a) porphirin b) teîrabenzopoıphirin c) porphirazin d) phthalocyanine Metallo phthalocyanines have important uses as commerciaî dyes, pigments, optical and eîectrical maîerials and catalysts. At the same time, they are being examined as advanced materials and their properties are compared îo those of the vii porphyrine complexes in hope of arriving at an understanding of how these naturally occuring maerocyclic compounds function. Although tetrabenzoporphyrines and porphyrazines are structural analogues of porphyrines and phthalocyanines, they have not been investigated so intensely due to the difficulty in reaction conditions and preparationof starting materials. One of the most important properties of tetrapyrroi ligands is their ability to coordinate to metal ions, yielding stable intercomplex salts. Stable campiexes of porphyrins, porphyrazines and phthalocyanines result from formation of four equivalent a bonds (N- >M) that is filling of vacant S, Px,Py and (n - 1) dx2 _y2 or ndx2-y2 orbitals of the cation with 0 electrons of the central nitrgen atoms which are called as coordinating N atoms. The resulting a bonds are strong that in the case of metals Cu2+, Ni2^~, Co2* and Zn2+ that in solid complexes practically no repicement of the metal ions takes place at H2 S04 concentrations ranging from 2 to 7 m. In the case of coordination of triply or quadrupiy charged ions the formation of a complex involves, in addition to d, s, and p2 orbitals, pz and dz orbitals that participate in the attachment of the extra ligand along the z - axis perpendicular to the plane of the molecule. The formation of a bonds (N- >M) in porphyrine and porphyrazine complexes leads to four electron pairs of the coordinating nitrogen atoms being excluded from the conjugation. The antibonding 71 orbitals (71*) of the macroring are filled with the heteraatomic n orbitals. The attendant decrease in the energy of these antibonding % orbitals favors conjugation of the heteroatomic n electrons which have not taken any part in the coordination to the metal. As a result the remaining n electrons acquire a 7t rather than a g character and are not easily protonated with acids. In many cases where the metal ion has filled d orbitals of % symmetry (d*,., dxz. dyz) it forms backward dative % bonds with the1 maerocyclic tetrapyrroi ligand. The metal serves as a donor of n electrons and the ligand as their acceptor. These bonds are opposite in direction to a bonds, that is M- »N, and are called backbonding. The d" electrons of the metal fill the antibonding n orbitals of porphyrazine. The filling of antibonding k orbitals increases their energy, which prevents the n electrons of the meso N atoms from entering into a n conjugation as well as enhancing their a character and capacity for acid protonation. In addition to electronic and charge effects of coordination complexes with cyclic k ligands such as porphyrines, phthalocyanines, porphyrazines and other macroheterocyclic compounds, may in some cases display steric effects of coordination. If coordination distorts the planar structure of a conjugated cyclic system, the conjugation of n electrons of the nitrogen atoms with the macroring ~ system weakens. As a result the basicity of the molecules increases. If coordination to a metal creates a more coplanar % system than the ligand, the opposite is true. Porphyrazines may be considered to be structural hybrids of the well - studied Viil porphyrines and phthaiogyanines. As such, they provide an excellent opportunity to explore the subtle effects of ligand structure on the properties of coordinated metal ions in porphyrinic complexes. In addition, porphyrazines show several unique properties (optical, electrochemical, and catalytic) which make them of interest in their own right. Despite the structural similarities, porphyrazines are virtually unstudied compared to the related macrocycies, partly due to the lack of an efficient synthesis of soluble derivatives. Octakis (pheyl) derivative, first reported by Linstead 60 years ayo, have received scattered attention. Despite the further efforts of Linstead in 1950's, no great improvement was made in porphyrazine synthesis or solubility over the next 30 years until Schram and Hoffmann have published a general, high yield route to octakis (alkylthio) porphyrazines in 1980. These readily soluble derivatives with eight electron donating alkylthio - substituents are naturally richer in electron density that the unsubstituted parent molecule. Further works in the five years to obtain new alkylthio - derivatives have reached to crown ether derivatives with S2 03 - donor groups. Onthe other side. Fitzgerald et al. Have reported new methods to convert alkynes into aikyl - or aryl - substituted maleonitriles which serve as arich souree of starting materials for cyclocondensations into soluble porphyrazines. Because of their biological relevance and structural similarity with phthalocyanines, our aim has been to prepare soluble porphyrazine complexes and further elaborate these structures into hexa - coordinated monomers or " shish - kebap" type oligomers by making use of suitable monodentate or bidentate iigands such as pyridine, cyanide or pyrazine. For this purpose, cobalt and iron have been chosen as the central metal ions in the inner core of porphyrazine. As proposed by Linstead, unsaturated 1,2 - dinitrile derivative should be prepared as the starting material. Disodium salt of dithiomaleonitrile (1), obtained from simple reactants sodium cyanide and carbondisuifi.de in two steps, was preferred as the starting point. Alkylation of disodium salt of maleonitrile (1) with octylbromide in methanol gave 1,2 - bis (octylthio) - 1,2 - dicyano - ethylene (2) which was in cis - form and easily soluble in benzene, chloroform, and dichlormethane ( Scheme 1). In the IR spectrum 2 gives a sharp intense peak at 2125 cm*' for C=N groups. ? 2CgH17Br MeOH__ X NaS^ ^CN CgH17S^ TN Scheme 1 1,2-Bis (oktyltio) maleonitrile. IX Cycloîeîramerization of 2 into porphyrazine was accomplished by making use of the template effect of magnesium ions. The optimal condition was to carry out the reaction in butanol in reffux temperature for 12 h. Octakis (octylthio) porphyrazinato magnezyum (Mg Pz) was very soluble in most of the common solvents except methanol and ethanol (Fig 2). Figure 2. Octakis (octylthio) porphyrazinato magnesium ( Mg Pz). In the mass spectrum of Mg Pz, the moleculer ion peak is observed at m/z 1488 as expected. The IR spectrum shows that nitrite groups are missing alter cyclocondensation and the C - H stretching vibrations of alkyl substituents are the most intense absorptions. ' H NMR spectrum of Mg Pz in deutorated chloroform cherly indicates the methylene protons in a - (3,74 ppm), P - (1,63 ppm), % ~ (1-42 ppm) positions to sulfur. The intense blue colour of Mg Pz is a consequence of Q absorption at 675 nm. This single band for Q absorption confirms the D4h symmetry as encountered in metallophthalocyanines. The effect of 5 - donors is also ciear, since Q band absorption is at 600 nm in octaethylporphyrazinato magnesium and their effect is comparable with benzo - condensation in phthalocyanines. The metal - free derivative (H2 Pz) was obtained by treating Mg Pz with strong acids, e.g. trifluoro acetic acid. The yield of the reaction was sufficiently high (94 %). Mass spektrum of H2 Pz obtained by FAB technique gives the molecular ion peak at m/2 1468,2 which is in accordance with the calculated value of 1468,55. When the IR spectrum of Mg Pz and H2 Pz are compared, stretching vibration of the inner core N - H group at 3250cm ~l H2 Pz is the only difference. The lower symmetry in H2 Pz (i.e. Da) is clearly indicated by the splitting of Q absorption at 714 and 650 nm. This property is also in parallel with that of phthalocyanines. Figure 3. Metal - free porphyrazine (H2 Pz). Metalloporphyrazines other that magnesium derivative is prepared by treating metal - free derivative with the metal salt in a suitable solvent. There is no other way reported in the literature to prepare metalloderivatives. Co Pz was prepared from H2 Pz and Co - acetate in a mixture of 2 - chloroethanol and ethanol (Fig 4). Mass spectrum of Co Pz gives the moleculer ion peak at m/z 1525,4. Its Q band absorption is at 645 nm indicating the metallation in the inner core. When planar XI Figure 4. Octakis (octylthio) porphirazinatocobalt (II). Co" complexes are reduced to Co1, then a non - bonding electron pair is present perpendiculer to the plane of the molecule and it reacts very easily with alkyl halides to give organo - cobalt compounds. Treatment of Co Pz with NaBFL* in ethyleneglycoldimethyl ether decreased the intensity of Q and B bands and led to a new absorption around 570 nm which was accepted as a typical cansequence for N4 Co complexes. Withount isolating this product, the reaction mixture was treated with alkyl halides or acetic anhydride and a new Co (III) compound was obtained as follawed by the changes in the colourof the mixture (Scheme 2). c£pz--*CqPz C8HI7 S 1 C-CH3 2 CH3 2 CH(CH3)2 4 CC%-CH3 Scheme 2. Synthesis of the alkyl porphyrazinatocobalt (ÎTİ) xn In UV - VIS spectra of these Co"'* dervetives, Q absorptions are around 635 - 645 nm and no shoulders on the high energy side of this peak is present which can be accepted as a proof for lack of aggregated species. Co - phthalocyanines have been extensively investigated by Hanack to prepare one - dimensional polymers through cyano bridges and these compounds have been shown to be semiconductants. In order to obtain analogues materials with porphyrazines, Co Pz was treated with K CN in acetone and air was bubbled through it. The product was an octahedral Co - complex of K [Co Pz (CN)2] formula which was confirmed by a C=N peak at 2130 cm"1 in the IR spectrum and the typical Q band absorption, around 678 nm. Elimination of KCN from this dicyano compound was easily accomplished by treatment with water at 80° C. The oligomeric structure was verified by the decrease in the intensity of the C=N band in the IR spectrum and the shift of the Q band absorption slightly to higher energy in the visible spectrum (Scheme 3). Iron phthalocyanines have been also under focus to prepare complexes of various oxidation state and " shish kebap " type oiygomers. Similar investigations on the porphyrazine derivatives were carried out during this study. Iron insertion into the metal - free H2 Pz was carried out in acetic acid and Fe - acetate was used as the iron source. RS\ T DC* RS RS 1. i RS. K[CoPz(CM)2] __ L RS T SR RS T SR RS p£ RS RS R=%h17 Scheme 3. p-Cyano octakis (octyltiyo) porphyrazinatocobalt (III) Although the reaction was carried out under inert atmosphere trace amount of oxygen led to Fem derivatives. Further exposure to air was certain during the work up procedures, so Fe Pz CI was isolated when excess iron had been expelled by treatment wite H CI solution (Scheme 4). xiij H2PZ « Fe{CH3COO)2 R\ SR N-ANX^N RS sr Scheme 4. Monochloro octakis (octyltio) porphyrazinatoiron. The visible spectrum of Fe Pz CI is completely different than other D4h compouds of porphyrazine. There are one intense peak at 594 nm and two others at 509 and 767 nm. Treament of Fe Pz CI with pyridine at reffux temperatures gave immediate changes in the colour of the solution and it was further confirmed with the visible spectra. The Q band region was the same as the other D4h compounds with a maximum at 645 nm. This product was assigned to be Fe Pz (Py)2 octahedral complex (Scheme 5). Ff PzCî + Py RrCgHt7 Scheme 5. Bipyridin octakis (octyltio) porphyrazinatoiron xiv When Fe Pz CI was reacted with bidendaîe N - donor ligand pyrazine for 36 h, the central metal ion was again divalent iron (II) coordinated to pyrazine donors from two sides to from a shish kebap type oligomer (Schemeö). In conclusion we can say that pophyrazines with eigh alkylthio substituents have very similar properties with phthalocyanines. Scheme 6. p. - pyrazine octakis (octyltio) porphyrazinatoiron
Description: Tez (Doktora)--İTÜ Fen. Bil. Enst., 1997.
Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 1997
URI: http://hdl.handle.net/11527/16323
Appears in Collections:Kimya Lisansüstü Programı - Doktora

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