Taç eter sübstitüe yeni ftalosiyoninlerin siklik voltametri ile incelenmesi
Başlık çevirisi mevcut değil.
- Tez No: 46196
- Danışmanlar: PROF.DR. NÜKHET TAN
- Tez Türü: Yüksek Lisans
- Konular: Kimya, Chemistry
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1995
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 93
Özet
ÖZET Ftalosiyaninler genellikle ftalonitril ve bunların çeşitli türevlerinden (örneğin ftalimid, ftalik asit vb. ) metalsiz olarak ve metal tuzlarıyla tercihen yüksek sıcaklıklarda metalli olarak elde edilmektedirler. Ayrıca o -pozisyonunda halojen içeren çeşitli aromatik bileşikler de CuCN ile reaksiyona sokulursa ftalosiyanin oluşmaktadır. Elde edilen ftalosiyaninler genellikle mavi renkli, yüksek ısıya ışığa ve asitlere karşı dayanıklı, fakat çözünürlüğü çok az olan bileşiklerdir. Bu çalışmada sentezlenmiş olan taç eterlere sulfanil köprüleriyle substitüe olmuş metalsiz ftalosiyanin ve Co(II), Ni(II) ve Zn(II) komplekslerinin, dimetilsulfoksid, dimetilformamid ve diklorometan içerisindeki siklik voltametrileri incelenmiştir. Destek elektrolit olarak 0.1 M tetrabutilamonyum perklorat kullanılmıştır. Buna ilaveten.destek elektrolitin difüzyon katsayısına olan etkisini gözlemleyebilmek için, dimetilsulfoksid içeri sindeki tetrabutilamonyum konsantrasyonu beş kat arttırılarak denemeler yapılmıştır. Bütün bu yapıların siklik voltametri incelemelerinde üç-elektrodlu bir hücre oluşturulmuş, ölçümlerinde de bilgisayara bağlı PARC 273 potensiostat-galvanostat (EG & ) ' dan yararlan ı İm ı şt ı r. Voltamogramlar x-y kaydedicisi (RE 0091) üzerine kaydedilmiştir. vıiAnahtar Kelimeler : Siklik voltametri, taç eter sübstitüe ftalosiyanin, Co(II), Ni(II), Zn(II) kompleksleri. Özet : Sülfanil köprüleri ile sübstitüe taç eterler içeren yeni bir ftalosyanin ve Co (II), Ni(II), Zn(II) komplekslerinin dimetilsülf oksid çözeltisinde destek elektrolitin (tetrabutilamonyum perklorat) iki farklı konsantrasyonu ve dimetilformamid ve diklormetan içerisinde siklik voltamogramları incelenmiştir. Bu bileşiklerin dimetilsülf oksid, dimetilformamid ve diklormetanda ki siklik voltamogramlarının katodik pik akımları (ip) tarama hızının karekökü ile orantılıdır. Bu komplekslerin indirgenme ve yükseltgenme dalgaları ile ilgili difüzyon katsayıları Randies -Sevcik denklemi kullanılarak hesaplanmıştır. Difüzyon katsayılarının değerlerinin düşük oluşu moleküllerin büyük oluşu ve çözeltide agregasyon yapmaları ile ilgilidir. Heterojen elektron transferi yavaştır, dolayısıyla katodik ve anodik pik uzaklıkları tarama hızıyla değişmektedir. CYCLIC VOLTAMMETRTC STUDIES ÜF NOVEL PHTHALÜC¥ANİKE£5^ SüBSIMr'rm.'EÜ WITH CROWN ETHERS THROUGH SULFANYL BRIDGES Dilek COŞKUNER Keywords : Cyclic Voltammetry, phthalocyanine substituted with crown ethers through sulfanyl bridges and its Co (II), Ni(II), Zn(II) complexes. Abstract : The cyclic voltammetry of a novel metal free phthalocyanine substituted with crown ethers through sulfanyl bridges and its Co (II), Ni(II) and Zn(II) complexes has been investigated in dimethyl sulphoxide solution for two different concentrations of the supporting electrolyte ( tetrabutylammonium perchlorate) and also in dichloromethane and in dime thy lformamide. The cathodic peak currents in the cyclic voltammograms of these species in dimethyl sulfoxide, dimethyl formamide and dichloromethane are proportional to the square root of the sweep rate. The diffusion coefficients associated with the waves of all these complexes were calculated using the Randles-Sevcik equation. The values of the diffusion coefficients obtained for the metal-free phthalocyanine and its complexes are low since it is consistent with the larges size of the molecules and with the aggregation of the molecules in solution. The heterogeneous electron transfer is relatively slow, so that the separation between the cathodic and anodic peaks varies with the sweep rate.
Özet (Çeviri)
Since their early synthesis this century, phthalo- cyanines have established themselves as blue and green dyestuffs par excellence. They are an important industrial commodity (output 45.000 tons in 1987) used primarily in inks (especially ballpoint pens), coloring for plastics and metal surfaces, and dyestuffs. More their use as photoconducting agent in photocopying machines heralds a resurgence of interest in these species. In the coming decade, their commercial utility is expected to have significant ramifications. Thus future potential uses of metal phthalocyanines, currently under study, include sensing elements in chemical sensors, electrochromic display devices, photodynamic reagents for cancer therapy and other medical applications, applications to optical computer read/write discs, and related information storage systems, catalysts for control of sulfur effluents, electrocatalysis for fuel cell applications, photovoltaic cell elements for energy generation, laser dyes, and molecular metals and conducting polymers. In addition to their extensive use as dyes and pigments, phthalocyanines have found wide applications in catalysis, in optical recording, in photoconductive materials, in photodynamic therapy and as chemical sensors. For this broad range of applications the stable phthalocyanines core should be amenable to modifications which can be accomplished either by changing the central metal ion or by adding functional groups on the periphery. By a judicious choice of substituents with suitable donor groups on the periphery, one can direct the phthalocyanine interactions with metal ions or with one another; the consequences of these phenomena will appear in affecting the ordering of molecular assemblies in the solid state as well as in solution. Drastic changes occur in the absorption spectra and photophysical properties when strongly conjugated macrocycles such as phthalocyanines are forced to lie in face to face conformations. Although phthalocyanines with N- or 0- donor substituents have been frequently encountered, those with thioether moieties are rather few. The latter group contains essentially products obtained by the cyclotetramerization of thioether substituted phthalonitriles which themselves have been derived by nucleophilic displacement reactions of dinitriles. VlllThe physical and chemical properties of soluble phthalocyanines have recently attracted much attention from materials chemist for their potential use in semiconducting materials, non-linear optics, and other optical devices [28fr At the same time, since they effectively absorb in the lower energy region of visible light, they have found extensive application as photoconductors in optical recording materials as well as photosensitizers in photodynamic therapyf323« The advantage of using soluble phthalocyanines for these applications, incontrast to the insoluble parent phthalocyanines, is the possibility to reach high purification degrees by column chromatography or crystallization [ 33 ]. Incorporation of macrocyclic groups such as crown ethers, tetraaza- or diazatrioxa- macrocycles onto the periphery of phthalocyanines has enhanced the solubility of these compounds and provided additional sites for different kinds of ions [8-14]. At the same time additional binding sites for different kinds of ions have been provided. The macrocyclic substituents also bring about novel features such as ion channel and mesophase formation when the macrorings are integral parts of the inner core by way of enhancing the planarity of the molecules [ 15]. Metallophthalocyanine redox species have been observed as intermediates in a variety of catalytic processes. Such complexes exhibit a rich electrochemical behaviour due to the accessibility of a range of oxidation states centered on the phthalocyanine ligand and for some transition-metal phthalocyanines on the central metal. Electrochemical studies of phthalo cyanines have concentrated mainly on complexes of the first-row transition metals, with only a few reports on those of the second and third row[ 30]. Few results have been reported on the redox changes trigged in the phthalocyanines by substituents attached to the macrocycle. Only a few tetrasubstituted and octa- substituted phthalocyanines appear to have been studied [34]. Metallophthalocyanines have been used as photo- catalysts or electrocatalysts in the reduction of methyl viologen, the reduction of oxygen, the oxidation of water and the reduction of carbon dioxide. In this latter connection, carbon dioxide is reduced in many aqueous solutions to formic acid. In aprotic solvents, carbon monoxide or oxalic acid are formed [23']. The redox behaviour of metallophthalocyanines has been the subject of much investigation. Rollman and Twamoto[35'] reported the half-wave potentials on polarography and at a rotating platinum electrode for a number of tetra- sulphonated examples in dimethyl sulphoxide. The cyclic- voltammetry of two phthalocyanines with sulfonated 17- membered diazatrioxamacrocycles (Cu, Co) was investigated in both aqueous and dimethylsulphoxide solutions. The IXeffect of the solvent was discus sed[ 31]. Oxydo-reduction behaviour of copper (II) phthalocyaninate substituted with four 15-membered tetraazamacrocycles and its pentanuclear complexes have been also reported [27]. In this present work, the cyclic voltammetry of a novel metal-free phthalocyanine substituted with crown ethers through sulfanyl bridges and its Co (II), Ni(II), and Zn(II) complexes has been investigated in dimethyl - sulphoxide solution for two different concentrations of the supporting electrolyte ( tetrabutylammonium perchlorate) and also in dichlorome thane and in dimethyl- f ormamide. M 2H Co11 Ni11 Zn11 Fig.l. Phthalocyanines Substituted with Crown Ethers Through: Sulfanyl Bridges Triple-distalled and spectrosol grade dimethyl- sulf oxide, dimethyl f ormamide and dichloromethane, dried over 4A molecular sieves, were used in the voltammetric experiments. Tetrabutylammonium perchlorate (TBAP) (0.1 M and 0.5 M) was used in dimethylsulf oxide and (0.1 M) indimethylformamide and in dichloromethane as supporting electrolyte. Solutions were purged with nitrogen prior to each voltammetric measurement. Cyclovoltammetric measurements were performed on a PARC 273 potensiostat/galvanostat (EG&G) interfaced with an external computer. A standard three-electrode cell configuration was employed using a Pt plate (area 0.55cm2) working electrode, a Pt wire counter electrode and a saturated calomel reference electrode (SCE). Voltammograms were recorded on the x-y recorder (RE 0091). After addition of a 0.1 M amount of TBAP as supporting electrolyte, the electrochemically available potential range was checked prior to use. The cyclic voltammograms of the metal-free phthalo- cyanine in dimethylsulf oxide, dimethylformamide, and dichloromethane in the presence of 0.1 M tetrebutyl- ammonium perchlorate as a supporting electrolyte have been observed in the potential range of +0.5 V to -1.5 V respectively. The cyclic voltammogram of this compound is characterized by two one-electron reduction waves in DMSO. These waves show quasi-reversible behaviour at all sweep rates studied. The heterogenous electron transfer is relatively slow, so that the separation between the cathodic and anodic peaks varies with the sweep rate. In dimethylformamide the cyclic voltammetry of this species showed one single-electron reduction peak. This cathodic wave has an irreversible character. On the other hand, in dichloromethane, and 0.1 M tetrabutylammonium perchlorate four one-electron quasi-reversible waves are observed for this compound. The reduction peak occur at more negative potentials in dichloromethane when compared with the potentials in dimethyl sulfoxide and dimethyl formamide. The cyclic voltammogram of the Co (II) complex of this phthalocyanine species has two quasi-reversible one- electron couples in dimethylsulf oxide and 0.1 M tetra butylammonium perchlorate. In this Co (II) complex the ratio of anodic to cathodic peak currents differs from unity and depends on the switching potential, demonstrating presence of the coupled chemical reactions. The behaviour of this complex in cyclic voltammetry in dimethylformamide and 0.1 M tetrabutylammonium perchlorate showed three one-electron reduction peaks. The third reduction peak disappear at sweep rates above 0.100 Vs"1. This may be result of a slow follow-up chemical reaction. In dichloromethane electrochemical measurements were performed at around 10 °C. The vapor pressure of this solvent is high, it is difficult to maintain constant composition because of solvent evaporation. Aggregation of this species at that temperature makes the measurements complicated. Thus the surface state of the xisolid electrode is modified. So well defined redox responses are not obtained. In this solvent and 0.1 M tetrabutylammonium perchlorate, only one single-electron reduction appears. In the case of the Ni(II) species cyclic voltammo- gram in dimethylsulf oxide using 0.1 M tetrabutylammonium perchlorate two one-electron reduction waves were observed. On the other hand, in dimethylformamide two cathodic single-electron peaks and in dichloromethane two one-electron reduction couples appeared. These waves except the second reduction one in dimethylformamide show quasi-reversible behaviour at all sweep rates studied. For this Ni(II) species the first oxidation and the first reduction peaks may be attributed to the ring oxydo- reductions. The cyclic voltammograms of Zn(II) phthalocyanine substituted with crown ethers through sulf anyl bridges in dimethylsulfoxide four quasi-reversible one-electron reduction waves were observed. In the case of the complex the reduction peaks corresponding to the ring reduction shift to less negative potentials. In dimethylformamide two reduction waves and in dichloro methane one one-electron reduction wave appeared. The cathodic peak currents Ip in the cyclic voltammograms of these species in dimethylsulfoxide, dimethylformamide and dichloromethane are proportional to the square root of the sweep rate v. The diffusion coefficients associated with the waves of all these complexes were calculated using the Randles- Sevcik equation. The values of the diffusion coeffici ents obtained for the metal-free phthalocyanine and its complexes are low since it is consistent with the larger size of the molecules and with the aggregation of the molecules in solution. Diffusion coefficients decrease with charge. This is a reflection of two effects; as the charge increases, the size of the solvation shell increases; metal ions may coordinate the solvent molecules, but with increasing charge outer-sphere solvent molecules are also oriented about the ion. Thus a large aggregate with its solvation sheath moves through solution more slowly. The dependence of D on ionic charge is qualitatively reasonable. So in the case of these phthalocyanine compound in the anodic regions diffusion coefficients appear to be smaller than those in the cathodic regions. On the other hand diffusion coefficients are not increased, if proportional to the increase in the concentration of supporting electrolyte (except for the diffusion coefficients for Zn(II) complex which is increased compared with 0.1M TBAP). Since the Zn(II) complex is quite soluble in dimethylsulfoxide, the aggregation may not be important. xii
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