Farklı sübstitüentler içeren yeni ftalosiyaninlerin oksidasyon-redüksiyon davranışlarının siklik voltametri ile incelenmesi
Başlık çevirisi mevcut değil.
- Tez No: 55726
- Danışmanlar: PROF.DR. NÜKHET TAN
- Tez Türü: Yüksek Lisans
- Konular: Kimya, Chemistry
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 100
Özet
ÖZET Ftalosiyoninler genellikle mavi renkli ve asitlere ya da bazlara karşı dayanıklı fakat çözünürlüğü çok az olan bileşiklerdir. Bir çok sentez metodları bilinmekle beraber ftalosiyoninler daha çok ftalonitril ve bunların ftalimid, ftalik asit gibi türevle rinden metalsiz veya yüksek sıcaklıklarda metatli olarak elde edilebilmektedirler. Bu çalışmada (a) -NO2, NH2, ve -S(CH2)nCH3 grupları ile substitue olmuş metalsiz ftalosiyanin ve onun Co(II), Zn(II) komplekslerine ait siklik voltametriler 0.1 M tetrabutilamonyum perklorat destek elektrolit ile diklorometan ve tetra- hidrofiıranda (b) -N02, NH2, -S(CH2)2N(CH)3 ve -S(CH2)2N+(CH3)3S04" grupla rıyla substitue olmuş (1), (2) ve (3) no'lu metalsiz ftalosiyonin bileşiklerine ait siklik voltametrik çalışmalar dimetilsülfoksid ve dimetilformamid içinde tetrabutil amonyum perklorat ile tetraetilamonyum perklorat destek elektrolitleri varlığında gerçek leştirilmiştir. Bütün bu yapıların siklik voltametri incelemelerinde üç-elektrodlu bir hücre oluşturulmuş, ölçümlerinde de bilgisayara bağlı PARC 273 potensiostat-galvanostat (EG&G)'den yararlanılmıştır. Voltammogramlar x-y kaydedicisi (RE 0091) üzerine kaydedilmiştir. XV
Özet (Çeviri)
SUMMARY CYCLIC VOLTAMMETRIC STUDIES OF PHTHALOCYANINES SUBSTITUTED WITH -N02, NH2, -S(CH2)“ CH3 AND -N02, -NH2, S(CH2)2N(CH3)2, -SCCH^N^CH,), S04”GROUPS The field of coordination chemistry of macrocyclic compounds has undergone spectacular growth during the past 1 5 years. This growth has largely been due to the synthesis of a great number and variety of synthesis of a great number and variety of synthetic macrocycles which behave as coordinating ligands for metal ions. Coordination compounds containing macrocyclic ligands have been known and studied since the beginning of this century; however, until quite recently, the number and variety of these compounds was limited. Complexes of porphyrins, çorrins and phthalocyanines have been investigated because of their relation to important naturally occurring species containing macrocycles such as heme, cytochromes, or chlorophyll, or because of their potential as dye stuffs or pigments. 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. On the other hand, the physical and chemical properties of soluble phthalocyanines have attracted much attention because of their potential use in semiconducting materials, non-linear optics and other optical devices. 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 therapy. 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. The redox behaviour of metallophthalocyanines has been the subject of much investigation. In the last 20 years, the electrochemical behaviour of metal complexes have been studied by chemists. Expecially metal complexes containing macrocyclic ligands were used as photocatalyst, or electrocatalysts in the reduction of water, and the reduction of carbon dioxide. xviIn this present work (a) the cyclic voltammetry of a metal-free phthalocyanine substituted with NH2, -N02, -S(CH2)u CH3 groups and its Co(U), Zn(Il) complexes has been investigated in dichloromethane and THF solutions with the supporting electrolyte (tetrabutylammonium perchlorate) and (b) the cyclic voltammetry of metal - free phthelocyanine series substituted with N02, -NH2, -S(CH2)2 N(CH3)2, ( 1 ) and -S(CH2)2N+(CH3)3 SO4“ (2), (3) has also been investigated in dimethylsulphoxide and DMF solutions with two different supporting electrolytes (tetrabutylammonium perchlorate and tetraethylammonium perchlorate) in the same concentrations to identify the effect of the supporting electrolyte. Triple-distilled water and spectrosol grade dimethylsulfoxide, dimethyl- formamide, dichloromethane and tetrahydrofuran, dried over 4A molecular sieves were used in the voltammetric experiments. Solutions vere purged with nitrogen prior to each voltammetric measurement. Cyclovoltammetric tnasurements were performed on PARC 273 potensiostat/galvanostat (EG&G) interfaced with an external computer. A standart three-electrode cell configuration was employed using a Pt plate (area 0.55 cm2) working electrode, a Pt wire counter electrode and a saturated colomel reference electrode (SCE). Voltammograms were recorded on the x-y recorder (RE 0091). After addition of a 0.1 M amount of TBAP and TEAP as supporting electrolyte, the electrochemically available potential range was checked prior to use. The cyclic voltammograms of metal-free phthalocyanine substituted with -NH2 and -S(CH2)n CH3 groups in dichloromethane and THF with tetrabutylammonium perchlorate as supporting electrolyte have been observed in the potential range of +0.5 V to -1.5 V in CH2C12 while in THF this is between +0.5 V to -1.3 V respectively. The cyclic voltammogram of this compound is characterized by three one-electron reduction waves in dichloromethane. The first reduction wave at all sweep rates studied and the second reduction wave at sweep rates higher than 0. 1 Vs”1 show irreversible behaviour while the third reduction has a quasi-reversible behaviour. In the anodic region two one-electron oxidation waves with quasi- reversible character were observed. In tetrahydrafuran the cyclic voltammetry of this species showed three one- electron reduction waves. The first reduction and the oxidation peaks have quasi- reversible character while the second and the third reductions are irreversible at all sweep rates studied. The observed slopes are greater than 100 mV per decade. Thus the charge-transfer reaction in the cathodic reductions is intrinsically slow the electroactivity range in the solvent THF did not allow the observation the observation of all oxydo-reduction peaks. In contrast because the electroactivity limit in dichloromethane was -1.5 vs SCE in the presence of 0.1 M TBAP an additional oxidation peak could be identified. The cyclic voltammogram of the Co(II) complex of this metal-free pc substituted with -N02 and -S(CH2)n CH3 groups has three one-electron reductions in dichloromethane and 0. 1 M tetrabutylammonium perchlorate. On the other hand two one-electron reductions were observed in THF. All the reduction peaks occur at more negative potentials in dichloromethane when compared with the potentials in THF. xvuThe heterogeneous electron transfer rate is relatively slow so that the seperation between the cathodic and anodic peaks varies with the sweep rate in these solvents. For this Co(II) complex the ratio of anodic to cathodic peak currents differs from unity and depends on the switching potential both in dichloromethane and THF. The oxidation or reduction of the phthalocyanine ring directly reflects the electrostatic interaction between the ring and the metal [11]. The electrochemical measurements in THF and dichloromethane were performed at around 10°C. The vapor pressures of these solvents (dichloromethane and tetrahydrofuran) are 58.1 and 26,3 kPa respectively [13]. So it is difficult to maintain constant composition because of solvent evaporation. The interaction between the central metal ion and the phthalocyanine ring did effect the oxidation potential. The increase in the number of d electrons of transition metal shifted the oxidation potential to a lower side suggesting a strong coordination of nitrogen atoms in the ring to metal ion. In the case of the Zn(II) complex substituted with -NO2 and -S(CH2)uCH;i groups two one-electron reduction waves were observed in dichloromethane and tetrahydrofuran. But the potential range in tetrahydrofuran was between +1.3 V and -0.5 V/SCE while this was +0.5 V to -1.5 V vs SCE in dichloromethane. In the case of the complex the reduction peaks attributable to the ring reduction shift to less negative potentials. It is known from CV measurements that Zn phthalocyanine undergoes chemical oxidation at the ring rather than at the metal center resulting in the formation of a phthalocyanine 7t-cation radical [11]. If we compare the diffusion coefficients that were calculated using Randles- Sevcik equation, we can see that the diffusion coefficients decrease with charge. 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 diffusion on ionic charge is qualitatively reasonable [17]. For these phthalocyanines because the molecular weight in the complexes is larger than that of the metal-free species the diffusion coefficients in the case of the complexes are lower than those of the metal-free phthalocyanine. If we consider the cyclic voltammetry of the second type of the metal-free phthalocyanine series substituted with -N02 and -S(CH2)2N(CH3)2 as compound (1); -NO2 and -S(CH2)2N+(CH3)3S0'4 groups as compound (2) and substituted with -NH2 and -S(CH2)2N+(CH3)3SO“4 groups as compound (3); we see four quasi-reversible one-electron reduction for compound (1) five reductions for compound (2) and two reductions (the first is quasi-reversible one-electron and the second is reversible two- electron transfers) for the compound (3), in DMSO containing 0. 1 M TBAP. xviuIn the cyclic voltammograms of the species (2) and (3) in DMSO containing 0. 1 M TEAP as supporting electrolyte the reductions appeared approximately in the same regions as in the dimethysulfoxide - TBAP system. But small shifts in Ep values are observed (The compound (1) was not soluble in dimethylsulfoxide with tetraethlammonium perchlorate so it was not studied). For all these species the heterogeneous electron transfer rate is relatively slow so that the separation between the cathodic and anodic peaks varies with the sweep rate in dimethylsulfoxide. The ratio of anodic to cathodic peak currents differs from unity and depends on the switching potential, demonstrating the presence of the coupled chemical reductions. In the case of the cyclic voltammograms for these metal-free species in dimethylformamide with 0. 1 M tetrabutylammonium perchlorate, two reduction peaks were observed for the compound (1). At the scan rates up to 200 mVs'the first one- electron reduction is reversible but at the higher scan rates the mechanism changes and becomes quasi-reversible. For the second reduction wave at slow rates (up to 25 mVs”1) the mechanism is reversible two-electron transfer while the mechanism becomes irreversible one-electron transfer for the scan rates higher than 25 mVs"1. If we would compare the similar reduction peaks for the species (1) both in DMSO and DMF if could be seen that these reductions shifted to more negative potentials in DMF by the solvent effect. For compound (2) the cyclic voltammograms showed four reductions (only the fourth reduction is reversible two-electron transfer but the others are all quasi- reversible one electron transfers). In the case of DMF, the reduction peaks appeared approximately in the same regions but shifted to less negative potentials. For the cyclic voltammetry of compound (3) in DMF two one-electron reduction which are quasi-reversible were observed. These reduction peaks appeared in very different regions compared to the reductions of the some species in dimethyl sulfoxide. Since the solubility of compound (1) in DMF is lower than that of it in dimethylsulfoxide, aggregation may be expected and the surface of the electrode may be modified.So only two reduction peaks can be identified in DMF [18]. But for compounds (2) and (3) the solubility is high in dimethylformamide as in the case of dimethylsulfoxide thus the same number of reductions could be observed in both solvents. In order to establish the reversibility or quasi-reversibility in these solvents the rate constant k(Ep) for electron transfer at the CV peak potentials we calculated by using the Nicholson and Shain method [9] given by the equation; k(Ep)=2.18[DaFnv/RT] 1/2 XIXThe electron transfer rate constant is directly related to the sweep rate v, and the diffusion coefficient D. Thus it is possible to measure the potential dependence on the rate of electron transfer. If we compared the k(Ep) values for the compounds (1), (2) and (3) the major effect of the substituents on the redox characteristics is that the substitution by the aliphatic chains reduces significantly the electron tranfer rate constant k(Ep) [18]. The diffusion coefficients were also calculated and compared. It was seen that the compound (2) having the higher molecular weight than the others showed lower diffusion coefficients. These phthalocyanines were soluble in DMF so aggregation may not be expected and electroactivity is high thus results with an increase in the diffusion coefficients. If we compare the compounds (2) and (3) as a function of different supporting electrolytes the diffusion coefficients were higher in the case of tetraethylammonium perchlorate than that of tetrabutylammonium perchlorate. xx
Benzer Tezler
- Naftoksi veya kinolinoksi grupları içeren yeni hegzadeka sübstitüe ftalosiyaninler
Novel hexadeca substituted phthalocyanines containing naphthoxy or quinolinoxy groups
ÖZGE KURT
- Farklı sübstitüentler içeren kurşun ftalosiyaninler
Lead phthalocyanines containing different substituents
HATİCE ÇERLEK
Yüksek Lisans
Türkçe
2005
Kimyaİstanbul Teknik ÜniversitesiKimya Ana Bilim Dalı
PROF.DR. MAKBULE BURKUT KOÇAK
- Kinolin sübstitüe ftalosiyaninlerin sentezi, optik ve elektrokimyasal özelliklerinin incelenmesi
Synthesis and examination of optical and electrochemical properties of quinoline-substituted phthalocyanines
FUAT DAHİL
- Hacimli aromatik gruplar içeren ftalosiyaninlerin sentezi ve karakterizasyonu
The synthesis and characterization of some phtalocyanines derived from aromatic and bulky substituted phtalonitriles
ŞERİFE BAYAR
Yüksek Lisans
Türkçe
2009
Kimyaİstanbul Teknik ÜniversitesiKimya Ana Bilim Dalı
YRD. DOÇ. DR. HATİCE AKIN DİNÇER
