Sumaiya Hasnain

Metal-containing polyurethanes from tetradentate Schiff bases: synthesis, characterization, and biocidal activities

N,N′-bis(salicylidene)thiosemicarbazide Schiff base has been synthesized by the reaction of thiosemicarbazide with salicylaldehyde and then reacted with formaldehyde to generate phenolic groups, resulting in the formation of Schiff-base monomeric ligand. It was further incorporated with transition metals, Mn+2, Co+2, Ni+2, Cu+2, and Zn+2, to form Schiff-base metal complex, which was then polymerized with toluene 2,4-diisocyanate to form metal-chelated polyurethanes. Monomeric ligand, its metal complexes, and its metal polychelates were characterized and compared by elemental analysis, FT-IR, 1H NMR, thermal, and biocidal activities to evaluate the enhancement in physical and chemical properties on coordination with metal and on polymerization. SEM images of ligand and polymer metal complexes showed changes in surface morphology, while electronic spectra of polymer metal complexes were used to predict the geometry. Antimicrobial activities were determined by using agar-diffusion method with Staphylococcus aureus, Escherichia coli, Bacillus subtilis (bacteria), Aspergillus niger, Candida albicans, and Aspergillus flavus (yeast). The polymeric ligand had varied antibacterial and antifungal activities, enhanced after chelation and polymerization. Comparative results show that coordination of metal to the ligand enhances its physical and chemical properties which were meliorated on polymerization.

Synthesis, characterization and biocidal activities of Schiff base polychelates containing polyurethane links in the main chain.

The concept of combining metallo-polymers with urethanes offers a versatile approach for the synthesis of new polymeric materials. Polyurethane containing transition metals was synthesized by the reaction of Schiff base metal complex with toluene 2,4 diisocyanate. The proposed structures were confirmed by elemental analysis, (1)H NMR, (13)C NMR and FT-IR. The geometry is determined by UV-Visible spectra and magnetic moment measurements, which reveals that the Mn(II), Co(II) and Ni(II) complexes have octahedral geometry while square planer geometry is reported for Cu(II) and tetrahedral for Zn(II) complex. The antimicrobial activities are determined using the agar well diffusion method with Staphylococcus aureus, Escherichia coli, Bacillus subtilis (bacteria), Aspergillus niger, Candida albicans and Aspergillus flavus (yeast). All the polymeric metal complexes show comparatively good biocidal activity, which is further enhanced after polymerization.

Synthesis, spectral, and antibacterial screening studies of chelating polymers of bisphenol-A–formaldehyde resin bearing barbituric acid

A new polymeric ligand was synthesized by the reaction of bisphenol-A and formaldehyde in the basic medium, followed by condensation polymerization with barbituric acid in the acidic medium. Polymer metal complexes were prepared by reaction of this resin with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II). The polymeric resin and its metal polychelates were characterized by elemental analysis, FT-IR, 13C-NMR, and 1H-NMR spectra. The geometry of the polymer metal complexes was evaluated by electronic spectra (UV-Vis) and magnetic moment measurement. Thermal stabilities show an increased thermal stability of the metal polychelates compared to the ligand. The antibacterial activities of all the synthesized polymers were investigated against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli, showing good antibacterial activities against these bacteria. Cu(II) polychelate showed highest biocidal activity.

Metal-based Schiff base polymers: preparation, spectral, thermal and their in vitro biological investigation

New polymer metal(II) complexes have been synthesized using Schiff base ligand, synthesized by the condensation reaction of 2-hydroxyacetophenone and o-phenylenediamine. The ligand and polymer metal(II) complexes have been characterized by micro-analytical, UV–vis, FT-IR, 1H-NMR spectral studies, as well as magnetic susceptibility and thermal studies. On the basis of spectral studies, a square-planar geometry has been proposed for the copper(II) polymer metal complex; manganese(II) polymer metal complex shows octahedral geometry while other polymer metal complexes have shown tetrahedral geometries. The in vitro antimicrobial activity of the compounds is tested against the bacteria Escherichia coli, Pseudomonas aeruginosa, Bacillius subtilis, Staphylococcus aureus, Salmonella typhi, and the fungi Candida albicans, Microsporum canis, and Aspergillus niger by well diffusion method. The polymer metal complexes show stronger antimicrobial activity than the free ligand and thermal studies were promising after coordination. The polymers represent a novel class of metal-based antimicrobial agents providing large number of opportunities for thermal and antimicrobial applications.

Coordination polymers of glutaraldehyde with glycine metal complexes: synthesis, spectral characterization, and their biological evaluation

Glycine metal complexes were prepared by the reaction of glycine with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) in 1 : 2 molar ratio. Thereafter their condensation polymerization was done with glutaraldehyde to obtain polymer metal complexes. All the synthesized polymer metal complexes were characterized by elemental analysis, FT-IR, 1H-NMR, and UV-Vis spectrometry, magnetic susceptibility, and thermogravimetric studies. The analytical data of all the polymers agreed with 1 : 1 molar ratio of metal complex to glutaraldehyde and magnetic moment data suggest that PGG–Mn(II), PGG–Co(II), PGG–Ni(II), and PGG–Cu(II) have an octahedral geometry around the metal atom, whereas the tetrahedral geometry was proposed for PGG–Zn(II) polymer. The PGG–Mn(II) and PGG–Cu(II) showed octahedral geometry. Thermal behavior of the polymer metal complexes was obtained at a heating rate of 10°C min−1 under nitrogen atmosphere from 0°C to 800°C. The antimicrobial activities of synthesized polymers were investigated against Streptococcus aureus, Escherichia coli, Bacillus sphaericus, Salmonella sp. (Bacteria), Fusarium oryzae, Candida albicans, and Aspergillus niger (Yeast).

Biologically active and thermally stable polymeric Schiff base and its metal polychelates: Their synthesis and spectral aspects

New metal polychelates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) obtained by the interaction of metal acetates with polymeric Schiff base containing formaldehyde and piperazine, have been investigated. Structural and spectroscopic properties have been evaluated by elemental analysis, FT-IR and (1)H-NMR. Geometry of the chelated polymers was confirmed by magnetic susceptibility measurements, UV-Visible spectroscopy and Electron Spin Resonance. The molecular weight of the polymer was determined by gel permeation chromatography (GPC). Thermogravimetric analysis indicated that metal polychelates were more thermally stable than their corresponding ligand. All compounds were screened for their antimicrobial activities against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, (bacteria) and Candida albicans, Microsporum canis, Cryptococcus neoformans (fungi) by agar well diffusion method. Interestingly, the polymeric Schiff base was found to be antimicrobial in nature but less effective as compared to the metal polychelates. On the basis of thermal and antimicrobial behavior, these polymers hold potential applications as thermally resistant antimicrobial and antifouling coating materials as well as antimicrobial packaging materials.

Coordination Polymers: Preparation, Physicochemical Characterization, Thermal and Biological Evaluation of Thiosemicarbazide Polychelates

Coordination polymers were prepared by the condensation reaction of salicylaldehyde and thiosemicarbazide with formaldehyde, transition metal acetates Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). Structural and spectral properties have been studied by elemental, spectral (FT-IR, 1H NMR, and UV–Vis), and thermogravimetric analysis. The geometry of the chelated coordination polymers was confirmed by magnetic susceptibility measurements and UV–Visible spectroscopy. Antimicrobial screening was done against microbes such as Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Staphylococcus typhi, Candida albicans, Microsporum canis, Aspergillus niger. In vitro antimicrobial activity was determined by the Agar Well Diffusion method and result show that all the coordination polymers exhibited better antimicrobial activity than their parent polymeric Schiff base. Coordination polymers were found to be more stable than their corresponding ligand as deduced by on thermogravimetric analysis. Because of antimicrobial and thermal behavior, these coordination polymers have broad range of applications as thermally resistant as well as antimicrobial-biocidal and antifouling coating materials.