Halka ve zincir sübstitüenler içeren bazı yeni vic-dioksimlerin ve komplekslerinin elektrokimyasal davranışlarının incelenmesi
Başlık çevirisi mevcut değil.
- Tez No: 55829
- 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: 95
Özet
ÖZET Yeni vic -dioksimlerin sentezi, stereoizomerlerinin ayrılması ve oluşturuldukları komplekslerin incelenmesi konusunda pek çok çalışma yapılmıştır. Diaminoglioksimin Co(II) ve Co(III) kompleksleri, bilinen vic -dioksim komplekslerinden farklılıklar göstermiş ve bu komplekslerin yapılan x-ışınlan difraksiyonu ile kesin olarak belirlenmiştir. Anti ve amfi izomerleri izole edilip, farklı kompleksleri elde edilen l,4-difenil-2,3bis(hidroksiimino) piperazin ve l,3-difenil-2-tiokso- 4,5-bis(hidroksiimino) imidazolin'in sentezi disiyan-di-N- oksit ile yapılmıştır. Çeşitli kobalt kompleksleri hazırlanan asenaftilen 1,2-diondioksim, B,2 model bileşiği olarak dimetilglioksim kompleksleri ile karşılaştırılmıştır. Aynca anti- monokloroglioksimden çeşitli sübstitüe mono ve diaminoglioksimler elde edilmiş ve kompleksleri incelenmiştir. Oksimlerin geçiş metallerinin çoğu ile sağlam kompleksler verdikleri ve bu komplekslerinde metaller ile azot veya oksijen atomları üzerinden değişik şekillerde koordinasyon bağı yaptıkları görülmüştür. Bu çalışmada; sentezlenmiş olan uzun zincir sübstitüentli vic -dioksim ve Cu(ll), Co(II), Pt(II) komplekslerinin dimetilsülfoksid ve dimetilformamid içerisindeki siklik voltametrileri incelenmiştir. Destek elektrolit olarak 0. 1 M tetra-butilamonyum perklorat kullanılmıştır. Buna ilaveten halkalı sübstitüentler içeren yeni bir vic -dioksim ve tetranükleer ve uranil ile pentanükleer nikel-uranil komplekslerinin dimetilsülfoksid ve dimetilformamid içerisindeki siklik voltametrileri de incelenmiştir ve her iki tür viç-dioksim komplekslerinin elektrokimyasal davranışları karşılaştırılmıştır. Bütün bu yapılann siklik voltametri incelemelerinde üç-elektrotlu bir hücre oluşturulmuş, ölçümlerinde de bilgisayara bağlı PARC 273 potensiostat-galvanostat(EG- G)'den yararlanılmıştır. Voltamogramlar x-y kaydedicisi (RE 0091) üzerine kaydedilmiştir. MI
Özet (Çeviri)
SUMMARY ELECTROCHEMICAL BEHAVIOR OF SOME NOVEL VIC-DIOX1MES SUBSTITUTED WITH RINGS ADN CHAINS The chemistry of simpler inorganic systems which can mimic certain of the properties of naturally occuring complexes has been of long and continuing interest. The succesful design and synthesis of ligands capable of forming multinuclear complexes are of great interest for obtaining special effects in magnetic, optical and electrical properties. For this purpose, the ligand need to carry multidonor groups to be able to bind more than one metal ion simultaneously. Macrocyclic ligands can be considered as an important candidate for one of the components of these ligands. Although many examples of macrocyclic synthetic ligands contain identical donor groups being liable to coordinate with either hard or soft metal ions, a mixture of two or more donor sites has been also employed to tune the selectivity and stability. Incorporation of a yjc-dioxime moiety onto the macrocycle provides an efficient binding site for transition metal ions through formation of an MN4 core with additional two hydrogen bridges. It is known that the oximate group can function as a bridge between two metal ions through the imino nitrogen and the deprotonated oxygen to afford bi-and tri-nuclear complexes. The high stability of the complexes prepared with yjc-dioxime ligands has been extensively used for various purposes including model compounds or trace metal analysis. The significant chemical behavior of transition metal complexes very often depends on their facile redox properties. This is true to a large degree for the natural and synthetic complexes involving macrocyclic ligands. These substances undergo a diverse array of chemical reactions, such as ligand dehydrogenation, metal alkylation, ligand substitution and hydrogenation. The success of some of these reactions is intimately linked with the ability of higher and lower oxidation states of these complexes to function as reactive intermediates. The ability of macrocyclic ligands to stabilize a wide range of oxidation states of a coordinated metal ion has been amply demonstrated. It becomes highly significant, therefore, when the availability of an extensive series of macrocyclic complexes permits an opportunity, to provide a sound chemical basis for the evaluation of redox-structure relationships. Macrocyclic complexes of transition metals have been the subject of several studies concerning various aspects of stereochemistry and electrochemistry. Electrochemical studies on macrocyclic complexes have shed considerable light on the chemistry of such systems, including the stabilization of unusual metal oxidation states, the ease of oxidation or reduction of the central metal ion with respect to macrocyclic ring size and the degree and position of ligand unsaturation, and the reactivity of the ligand as a function of the site of electron donating or withdrawing substituents. The complexes present a unigue viaopportunity to study and correlate the significant changes in redox properties which occur as a result of changing the parameters. In this present work, the cyclic voltammeti ies of two novel different types of yjç- dioximes substituted with long side-chains (H2L) and with ring systems (LHL,) and their complexes have been investigated in dimethylsulfoxide and dimetil-formamide by using 0. 1 M tetrabutylammonium perchlorate as a supporting electrolyte. Triple-distilled water and spectrosol grade dimethyl-sulfoxide, dimethylformamide, dried over 4A molecular sieves, were used in the voltametric experiments. Tetra butylammonium perchlorate (TBAP) (0. 1M) was used in dimethylsulfoxide and dimethylformamide. Solutions were purged with nitrogen prior to each voltammetric measurement. Cyclovoltammetric measurements were petformed on a PARC 273 potensiostat interfaced with an external computer. A standard three-electrode cell was employed using a Pt plate working electrode, a Pt wire counter electrode and a saturated calomel reference electrode x-y recorder was used for taking voltammograms. The electrochemically available potential range was checked prior to use. The cyclic voltammograms of the novel yic-dioxime H2L have been observed both dimethylsulfoxide and in dimethylformamide in the presence of 0. 1 M tetrabutylammonium perchlorate as a supporting electrolyte. The cyclic voltammogram of this compound is characterized by two one-electron reduction waves in DMSO. These show quasireversible behaviour at all sweep rates studied. In dimethylformamide the cyclic voltammetry of this species showed two quasi- reversible one-electron reductions. These reductions appeared at less negative potentials than those in DMSO. In both solvents the variation of E,, with sweep rate changed from the quasi-reversible case to the charge-transfer rate determining case within the sweep rates studied [41]. The cyclic voltammogram of the dinuclear Cu(Il) complex of this vic-dioxiine presents three quasi-reversible one-electron reduction waves. The first reduction may be assigned to the Cu(II)/Cu(I) couple. The other two reduction peaks are responsible for the reductions centered in the ligand moiety. In DMF two single electron reduction waves were observed. The reduction peak 2 was approx. In the same region with the reduction wave of the ligand. But this reduction shifted to more negative potential. Cyclic voltammetry of the copper containing dinuclear complex clearly shows that the reduction proceeds in two distinct one-electron steps. After the first one-electron reduction, the redox properties of the second complexed transition metal cation are changed [44]. In the cyclic voltammogram of Pt(II) complex of H2L one-electron reduction one- electron oxidation peaks were observed. These peaks appeared in the same vicinity with the oxydo-reductive waves of the ligand. Thus these peaks can be attributed to the oxydo- reductions occured in the ligand. For Pt(II) complex two one-electron reduction waves appeared in DMF and did not appear in the voltammogram of ligand. The reduction peak IX2 was approx. In the same region with the reduction of the metal-free yjc-dioxime. In the anodic region peak 4 is reversible, i.e. the charge transfer reaction is intrinsically slow. The cyclic voltammograms of Co(II) complex of H2L species showed two one- electron reduction waves in DMSO and one-electron reduction peak in DMF. All these waves have quasi-reversible behaviour. In DMF the electron transfer mechanism was changed from reversible to irreversible case for the oxidation peaks have irrevesible character. For all these species the heterogenous electron transfer rate is relatively slow so that the separation between the cathodic and anodic peaks varies with the sweep rates studied. The cathodic peak currents Ip in the cyclic voltammograms are proportional to the square root of the sweep rate. This shows that the diffusion is the rate- limiting step. A typical voltammogram of the novel yjc-dioxime substituted with rings, LFL, showed two quasi-reversible one-electron reductions in dimethylsulfoxide and 0.1 M tetrabutylammonium perchlorate system. In dimethyl-formamide and 0.1 M tetrabutyllammonium perchlorate, the cyclic voltammogram of the same species presented three one-electron reduction waves. The reduction peak 3 has irreversible character but all the others are quasi-reversible waves. In this system the corresponding reduction peaks appear at more negative potentials than those in dimethylsulfoxide and 0.1 M tetrabutylammonium perchlorate. For mononuclear Ni(II) complex of this species, quasi-reversible one-electron reduction peak and two one-electron oxidation waves were observed. The only reduction peak in the cathodic region and in the anodic region peak 2 appeared approx. In the same oxydo-reduction vicinity of the oxime ligand. So these waves may be attributed to the oxydo-reductions in the ligand species. The peak 3 may be metal-centered [46,47,48]. In dimethylformamide and 0. 1 M tetrabutylammonium perchlorate the cyclic voltammagram of the mononuclear Ni(II) complex showed three quasi-reversible one-electron reduction waves. Peaks 1 and 2 appeared approx. In the same region of those in LFL,. Thus these peaks may be centered on the electron transfers in the ring system. The reduction peak 3 may suggest the reduction in the metal center. Three one-electron reduction waves appeared in the cyclic voltammogram of the tetranuclear U02(VI) complex of this species in dimethylsulfoxide and 0.1 M tetrabutylammonium perchlorate. The reduction peak 1 and oxidation peak 5 in anodic region may be attributed to the U02(VI) centered on the oxydo-reductions [50]. The other reductions may be attributed to the electron transfers in the ring system. The cyclic voltammogram of this complex in dimethylformamide and 0.1 M tetrabutylammonium perchlorate showed two quasi-reversible one-electron reductions. The first reduction appeared in a different region than that of the free yjc-dioxime. So it may be metal- centered. In the cyclic voltammogram of the pentanuclear U02(V1) Ni(II) complex showed three one-electron reduction waves and two oxidation peaks. In the anodic region peak 4 has two-electron transfers. It is reversible in character at sweep rates studied, and may be attributed to the phenanthroline ring oxidation [51]. However the cyclic voltammogram of this species in dimethylformamide and 0. 1 M tetrabutylammonium perchlorate showedonly one-electron reduction. In anodic region one two-electron oxidation existed This oxidation has reversible character. The reduction peak appeared in the same region of the metal centered reduction of the mononuclear Ni(II) complex. Thus this reduction may exhibit the reduction in the Ni(II) center. For all these dioxime species and its complexes studied the heterogeneous electron-transfer rate is relatively slow, so that the separation between the cathodic and anodic waves varies with the sweep rate. The variation of Ep with sweep rate change from the quasi-reversible or reversible case to the charge transfer rate determining case [41]. In all cases the cathodic peak current Ip in the cyclic voltammogram proportional to the square root of the sweep rate. is The diffusion coefficients associated with the waves of all these species were calculated using Randles-Sevcik equation. The values of diffusion coefficients obtained for these species in dimethylformamide are generally larger than those obtained in DMSO. In both solvents diffusion coefficients decrease with charge. Thus in the anodic region diffusion coefficients have lower values than those in the cathodic region. 0 f - Bu Ot-Bu Ot-Bu Ot-Bu Ot-Bu Ot-Bu Fig. 1. M= I'l(II), Cu(ll) complexes of H2L OH 0- N NVNX / N / Cu /u OH H OtBu OtBu OtBu OtBu OtBu -OtBu Fig. 2. Cu(ll) complex oflbL XIFig. 3. Mononuclear Ni(II) complex of LH4 (Ol ° h o rjû OH Fig. 4. Tetianuclear U02(1V) complex of LI I.t Ö NXN 9 0 9 01 0 Wx )Ni( x ^1 Fig. 5. I'enlanueleni U02(VI) Ni(ll) complex of LIU Xll
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