Yeni tip dallanmış vic-dioksim ve geçiş metal komplekslerinin sentezi

Abstract

Oksimler ve son yıllarda önem kazanmaya başlayan diğer bir madde grubu olan dendrimerler çeşitli özellikleriyle geniş ve yeni uygulama alanları bulmaktadırlar. Bu çalışmada sentezlenen oksim bileşiği ve metal kompleksleri de içerdikleri dendrimerlere benzer uzun zincirler nedeniyle bu tür moleküllerin daha kompleks yapıda olanları için yeni ve ilginç başlangıç maddeleri olma özelliğim taşımakta olup çoğu organik solventlerde çözünmektedirler. Bu iyi çözünürlük, sentezlenen yeni bileşiklerin yapılarının aydınlatılması için gerekli olan spektroskopik çalışmaları kolaylaştırmış, aynı zamanda reaksiyonlarının incelenebilmesini mümkün kılmıştır. Bu çalışmada 4-amino-4-[2-(tert-bütoksi karbonil) etil] heptandioat bileşiğinden yola çıkılarak literatürde bulunmayan yeni bir vic-dioksim türevi olan 1,2-Bis{[di- tert-bütil 4-amino-4-(2-(tert-bütoksi karbonil) etil) heptandioat]-N-yl}glioksim (H2L) elde edilmiş, daha sonra ilgili metal tuzlanyla Nikel(II), Palladyum(ü), Bakır(II), Kobalt(II) ve Platin(II) kompleksleri sentezlenmiştir. Elde edilen yeni maddelerin yapılan Elemöntel Analiz, İR, Mass, NMR, Atomik Absorpsiyon ve UV-VTS gibi ölçümlerle aydınlatılmıştır.

The coordination chemistry of vic-dioximates is an intensive area of study and numerous transition-metal complexes of this group of ligands have been studied. The exceptional stability and unique electronic properties of these complexes can be attributed to their planar structure which is stabilized by hydrogen bridges. Owing to their importance as stable MN4 core-containing coordination compounds, vic-dioxime complexes have been much investigated. We have initiated a series of studies on the chemistry of the transition metal complexes of vic-dioximes incorporating macrocyclic poh/ethers(e.g. crown ethers) thus generating a range of compounds capable of binding transition and alkali metal ions simultaneously and enhancing their solubility in various organic solvents. In addition to the traditional study of the alkali metal- binding abilities of crown ethers, many efforts have been directed recently towards combining these macrocyclic polyether units with additional donor sites in order to provide possible access to new functionalized materials. Vicinal dioximes have received considerable attention as model compounds to mimic bifunction such as reduction of vitamin B12. Their complexes have been the source, through the decades, of a never-ending series of interesting reports. Although extensively investigated under the tacit assumption of their bidentate involvement in metal-ion coordination, most studies are mainly based on spectroscopic evidence. The reaction of amines or thiols with (E,E)-dichloro gtyoxime or cyanogen di- N-oxide yielded various symmetrically substituted diaminoglyoxime or ditbioglyoxime derivatives. The (E,E)- and (E,Z)- stereoisomers of vicinal dioximes are capable of coordination through N,N or N,0 sites of the oxime groups, and only in a few cases it is possible to realize the interconversion of (E,E)- and (E,Z)- complexes. In the case of (E,E)-monochloroglyoxime, asymmetric vicinal dioximes have been obtained. The transition metal complexes of these vicinal dioximes are essentially N,N-coordinated square- planar structures, but the uranyl complexes form hydroxo-bridged dimers with -vii- N,0-coordination as shown by IR and H NMR spectra. Other types of vicinal dioxime complexes which have been investigated and compared with dimethylglyoximato analogs are transition-metal complexes of 5,6- dihydrocycjo pent[f,g]ace naphthylene-l,2-dione dioxime. In previous papers we have shown the synthesis of vic-dioximes and their transition metal complexes containing crown ethers, monoazacrown ethers, cyclopentadienyl groups, tetrathiamacrocycles or diazadioxa macrocycle. Our primary aim has been the synthesis of new vic-dioximes with various functional groups. According to this strategy we herein report the synthesis of a new vic-dioxime which can be considered as a starting material for dendrimers. The synthesis and spectral features of dendritic macromolecules have been recently reviewed. A first indication of new trends in dendrimer research can be found also in a report in 1991 by Newkome et al. The first studies on dendritic metal and non-metal complexes demonstrate that dendrimers can be attached to metal centers for the preparation of "supramolecular aggregates". The controlled complexation of metal ions at spesific binding sites in dendrimer cavities was achieved by Newkome et al., who prepared a dendrimer framework containing triple bonds, which could be complexed by dicobalt hexacarbonyl units. The synthesis of dendrimers is receiving world-wide attention in both academic and industrial laboratories. Up until to now the primary goal was the synthesis of dendrimers with high molecular mass and as many generations as possible. Poly(amidoamines), polypropylenamines and silicon dendrimers set "records" for the number of generations, whereas the polyacetylene dendrimer prepared by Moore et al. These first examples of cascade molecules with functional components point out the new directions in dendrimer research: Properties are modified increasingly with functional centers. Not the dendrimer itself but the multiplication of functional components attached to a dendritic skeleton moves into the forefront, and new materials with spesific properties (redox, ligand and liquid crystalline properties, biochemical activity...) are anticipated. -vni- An example of redox-active dendrimers was given by Bryce et al., who connected benzene tricarboxylic acid trichloride to ddendritic tetrathiafulvalene as a functional component. The cyclic voltammogram of this molecule indicates formation of a multiply positively charged species in which the tetrathiafulvalene units do not interact. Industry has also shown increasing interest in functional cascade molecules for applications in diverse areas such as medical engineering, agrochemistry and the development of photocopier toners. Furthermore the potential of dendrimers in pharmaceutical and medical applications, diagnostic imaging and radiation therapy is frequently discussed. Oligoamines were screened for anticancer properties. Dendrimers could have advantages over polymers with regard to viscosity properties and application in high-resolution lithography. Increasing industrial research on dendrimers should stimulate further investigations in this field. The first dendrimeric vic-dioxime l,2-bis{[di-tert-butyl 4-amino-4-(2-(tert- butoxycarbonyl) ethyl) heptanedioate]-N-yl}glyoxime (I^L) was prepared by the reactionofdi-tert-butyl4-amino-4-[2-(tert-butoxycarbonyl)ethyl]heptanedioate(2) with cyanogen di-N-oxide (Scheme 1). This ligand and its metal complexes are very soluble in common organic solvents such as methanol, chloroform, dichloromethane, n-hexane, etc. In the IR spectrum of H2L an OH stretching vibration is observed at 3220 cm"1. N-H, C=0, C=N and N-O stretching vibrations are at 3360, 1720, 1620 and 920 cm" respectively. These values are in harmony with the previously reported derivatives. In the lH NMR spectrum of P^L (in DMSO-d6) the OH and NH proton resonances appear as two singlets at 6 = 8.93 and 3.5 ppm respectively. These singlets disappear by deuterium exchange. A single chemical shift for OH proton indicate that the oxime groups are in the anti form. The 1H NMR spectrum exhibits signals for methyl protons at 1.39 ppm and methylene protons at 1.57- 2.43 ppm. These spectral data are aggreement with previously reported dendrimeric molecules. In the C NMR spectrum of H2L, methyl carbons were observed at 27.6 ppm. Other methylene carbons were appeared at 29.14 and 34.12 ppm. Quaternary carbons (C-NH2) and (C-CH3) were observed at 53.12 and 79.32 ppm respectively. The carbon resonance of amidoxime was found at 147.69 ppm. The molecular ion peak at m/z in the mass spectrum of H2L also -DC- confirms the proposed structure. Cyanogert-di-N-oxide -40C HON O OBut H2L Scheme 1 Synthesis of l,2-bis{[di-tert-butyl 4-amino-4-(2-(tert- butoxy carbonyl)ethyl)heptanedioate]-N-yl}glyoxime (H2L) The branched vic-dioxime derivative forms mononuclear complexes with Ni(II), Pd(II), Co(II) and Pt(II) with a metal-ligand ratio of 1:2 (Figure 1). The most fascinating feature of all these complexes is their solubility in various organic solvents. In all cases only the mononuclear complexes are formed even nN in the presence of excess metal ions (except for Cu ). ButO O ıw\j\* Bu<0 O O I M o. -V~^ n^n' njAn V08"' (J OBu» ButO Bu<0 BuC^O Figure 1 The structures of [M(HL)2] [M = Ni(II), Pd(II), Co(II) or Pt(II)] -x- The nickel(II) complex of H2L has a metahligand ratio of 1:2 and the ligand is coordinated only by the N,N' atoms of the vic-dioxime. It shows the characteristic features of vic-dioxime complexes. The reddish color of Ni(HL)2 is in accord with that of previously reported vic-dioximato complexes. In the IR spectrum, the O-H...O bridge is characterized by a broad absorption for the bending vibrations around 1705-1720 cm. The C=N bands due to oxime groups are observed at 1605-1620 cm". Proton NMR spectral data confirm the hydrogen-bridged structure with a chemical shift at lower field (5 15.6-17.6 ppm) for the deuterium exchangable OH protons. Also an NH proton has been observed at 8 = 4.39 ppm. Comparison of the C NMR data for H2L and its nickel(II) complex reveal a chemical shift for the carbon atom of the oxime moiety upon complexation. The diamagnetic nature of palladium(II) and platinum(II) complexes is confirmed by their H NMR spectra which show comparable shifts with those of Ni(HL)2. o Consequently we might conclude that both of these d metal ions are coordinated with dioximate donor sites in square-planar geometry. In the C NMR spectra, all peaks are approximately identical for the complexes of Pd(II) and Pt(II). Attempts to prepare the octahedral cobalt(III) complex by using pyridine or triphenylphosphine as axial ligands were not successful. In the case of copper(II) complex of H2L a new unusual feature was observed. As shown in Figure 2 the two copper atoms are linked to each other by chloride bridges. The structure is also confirmed by the mass spectrum of Cu2(HL)2Cl2 which gives a molecular ion peak at m/z 2024 using FAB technique. In the IR spectrum of this complex, the OH and NH stretching bands are observed at 3240 and 3340 cm respectively. Consequently we propose an N,0 coordinated structure in which the two molecules are bridged by two chlorine ions as encountered in some camphorquinone dioxime ligands. Because of the pale green color of this copper complex we were not able to observe an absorption in the UV-VIS spectrum corresponding to this coloration. The high solubility of the complexes in appropriate solvents enable us to investigate their spectrophotometric measurements. -xi- ButO, ButQ o O OH O. ButO^T H N~0/ Xc/ \N={ >^0 4, tt J^- OBu* ^N_fM-0But O / OH OBut II Figure 2 The structure of dinuclear copper complex