Synthesis, spectroscopic and structural characterization of Co(II)-pullulan complexes by UV-Vis, ATR-FTIR, MALDI-TOF/TOF MS and XRD. (15th November 2018)

• Record Type: Journal Article
• Authors: Mitić, Žarko; Nikolić, Goran M.; Cakić, Milorad; Nikolić, Goran S.; Živanović, Slavoljub; Mitić, Sanja; Najman, Stevo
• Is Part Of: Carbohydrate polymers. Volume 200(2018)
• Page Start: 25
• Page End: 34
• Publication Date: 2018-11-15
• Subjects: Co(II)-pullulan -- ATR-FTIR -- MALDI-TOF/TOF MS -- XRD; Polysaccharides -- Periodicals; Polysaccharides -- Periodicals; Polysaccharides -- Périodiques; Electronic journals; 547.78
• DOI: 10.1016/j.carbpol.2018.07.032
• Languages: English
• ISSNs: 0144-8617

Abstract

Graphical abstract: Highlights: Stable Co(II)-RLMP complexes were synthesized and isolated in the solid state. Co(II)-RLMP complex formation is confirmed by UV-Vis and ATR-FTIR spectroscopy. MALDI-TOF/TOF MS results confirmedd -Glc p as the RLMP repeating unit. XRD results show a low crystallinity form of Co(II)-RLMP. Different model structures of synthesized Co(II)-RLMP complexes are proposed. Abstract: Complexes of Co(II) ion with reduced low-molar pullulan (RLMP) ( Mw 6000 g/mol) were synthesized in aqueous solutions at boiling temperature in the pH range from 7.5 to 13.5. Obtained Co(II)-RLMP complexes, with cobalt content ∼2–8% (AAS), were characterized by UV-Vis spectrophotometry, FTIR spectroscopy (ATR-FTIR, FT-IRIS), MALDI-TOF/TOF MS, and XRD. Tetragonally distorted Oh coordination of Co(II) ions with O ligand atoms in synthesized complexes is suggested based on the spectrophotometric data. No influence of complexation process on the 4 C1 chair conformation of thed -glucopyranose units of pullulan was detected by ATR-FTIR measurements and FT-IRIS showed high homogeneity of synthesized complexes. Some additional depolymerization of pullulan during complex synthesis was indicated by MALDI-TOF/TOF MS but it also revealed good stability of complexes with much weaker binding of Co(II) ion in low molar mass fragments. Even in complexes with highest Co(II) ion content a low degree of crystallinity was detected by XRD analysis.