Correlation between UV-VIS spectra and the structure of Cu(II) complexes with hydrogenated dextran in alkaline solutions

Abstract

UV-VIS spectrophotometric investigations of Cu(II) complexes with hydroge-nated dextran showed that the complexation of Cu(II)-ions began at pH > 7. The formation of Cu(II) complexes with dextran monomer units was observed at pH 7-12. With further increase in solution pH > 12, the Cu(II)-dextran complex decomposed to Cu(OH)42~-ions and dextran. With increasing solution pH the absorption maximum of complex solutions increased and shifted to shorter wavelength (hypsochromic shift) compared with uncomplexed Cu(II). The UV spectra displayed bathochromic shifts. The changes of UV-VIS spectra with increasing in solution pH confirmed the formation of different kinds of complex species. The correlation between the results of UV-VIS spectrophotometry and the central metal ionligand coordination predicted that the copper binding within the complex depended on the pH and participation H2O molecules. Dextran complexes with Cu(II) were formed by the displacement of water molecules from the coordination sphere of copper by OH groups. The analysis indicated that the Cu(II) center was coordinated to two glucopyranose units of dextran. The spectrophotometric parameters of the investigated complexes were characteristic of a Cu(II)-ion in a square-planar or tetragon ally distorted octahedral coordination

Nano-biocomplexes based on oligosaccharides and their derivates

“…ESR parameters of the spectra for the complexes synthesized at higher pH values were close to the values for the frozen Cu(II)ethylene glycol complex indicating the square-planar or tetragonal distorted octahedral coordination of Cu(II) ion, with four oxygen atoms in the same plane. The appear-ance and ESR parameters for the spectra of complexes obtained at pH 8 and 12 were very similar to the ESR spectra of some Cu(II) ion complexes with carboxymethyl-dextran and cellulose obtained at high pH values [34,37]. Although the Cu(II) ion content of the complexes synthesized at lower pH values was much higher (up to 13.04% for the complex synthesized at pH 7.5), the ESR signal of these complexes was lacking due to strong spin-spin interactions of neighboring Cu(II) ions, and probably due to the formation of polynuclear Cu(II) complexes.…”

“…The synthesis and spectroscopic characterization of the Cu(II) ion complexes with RLMP and RLMD is described in detail [33,34,37].The formation of Cu(II)-hydroxyl complexes with deprotonated dextran monomer unit was observed in the range of pH 8-12. The results of spectrophotometric analysis indicate the possibility of the formation of coordination bonds which rearrangement begins at pH > 8.…”

Fourier-Transform IR spectroscopic investigations of Cobalt(II)–dextran complexes by using D2O isotopic exchange

“…The spectroscopic analysis showed that IR spectra of RLMD and its complexes with Co(II) ions are basically similar. Exactly let's say we know that by the complexing Cu(II) ion with dextran [18,20], and pullulan [15] in the dependence of the pH, form different types of the complexes, and the spectral picture in this region is very similar. The similarity of the spectra indicate that during the reaction of the samples, there is no change in the dextrans linearity γ(C-H) as well as no change in the C 1 chair conformation of glucopyranosyl units (910 and 840 cm −1 ).…”

Analysis of Bioactive Olygosaccharide-Metal Complexes by Modern FTIR Spectroscopy: Copper Complexes

“…The interaction of Cu(II), Ni(II) and Fe(III) ions with dextran may be used for their speciation by ultrafiltration (Solpan & Sahan, 1993). Synthesis procedures for the complex formation of Cu(II) ion with polysaccharides, including dextran, are described in scientific literature (Nikolic et al, 2005;Mitic et al, 2004;. In the section, we analyzed the IR spectra of Cu(II) ions complexes with reduced low molar dextran (RLMD).…”

“…5. The results obtained from the structural studies of the investigated complexes were based on other spectroscopic techniques (Nikolic et al, 2005;Mitic et al, 2004;Nikolic et al, 2004;Bartkowiak et al, 1998;Cakic et al, 2008). The changes in number, frequencies, intensity, and width of the FTIR bands in the particular region of ν(O-H) vibrations (3400 cm -1 ), δ(C-H) vibrations (1500-1300 cm -1 ) and ν(C-O) vibrations (1200-1000 cm -1 ) (Fig.…”