Nahid Nishat

Synthesis, characterization and anti-microbial studies of a newly developed polymeric Schiff base and its metal-polychelates

A new polymeric Schiff base containing formaldehyde and piperazine moieties has been synthesized by condensation of salicylaldimine, formaldehyde and piperazine in alkaline medium; its metal polychelates have also been synthesized with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) acetate. The synthesized Schiff base and its metal polychelates were characterized by elemental, spectral (IR, 1H NMR, UV-visible) and thermogravimetric analysis (TGA). Electronic spectra and magnetic moments indicate that Mn(II), Co(II) and Ni(II) polychelates show octahedral geometry, while Cu(II) and Zn(II) polychelates show square planar and tetrahedral geometry, respectively. All compounds show excellent anti-bacterial as well as anti-fungal activity against three bacteria and two fungi. The anti-microbial activities were determined by using agar well diffusion method, with 50 µg mL−1 and 100 µg mL−1 concentration of each compound tested against the microbes.

Synthesis, characterization, and biocide properties of semicarbazide-formaldehyde resin and its polymer metal complexes.

Semicarbazide-formaldehyde resin (SFRs) was prepared by the condensation of semicarbazide with formaldehyde in an acidic medium and its polymer metal complexes were prepared with transition metal ions. All the synthesized polymers were characterized by elemental analysis, FTIR, (1)H NMR, (13)C NMR, electronic spectroscopy, magnetic moment measurement and thermogravimetric analyses. The percentage of metal in all the polymer metal complexes was found to be consistent with 2:1 (resin: metal) stoichiometry. The magnetic susceptibility measurement and electronic spectra of all the polymer metal complexes confirmed the geometry of the complexes. All the synthesized polymeric compounds have been screened in vitro against Bacillus subtilis, Staphylococcus aureus (Gram-positive) and Escherichia coli, Salmonella typhi (Gram-negative) using shaking flask method. The entire polymer metal complexes showed excellent anti-bacterial activity and low toxicity when compared with their parental polymeric resin. The anti-bacterial activity and toxicity of the entire synthesized compound is significant and they can be used as antimicrobial as well as anticancer agents for mammals in future.

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, spectral and antimicrobial studies of a novel macrocyclic ligand containing a piperazine moiety and its binuclear metal complexes

A novel macrocycle 1,16-diaza-7,10-diamino-6,11-dioxo-1,17-bis[2′-hydroxy-5′-aminobenzyl]-piperazine-4,12-cyclododecadiene, [H4L] has been synthesized by a multistep process. The interaction of 5-amino salicylic acid, piperazine and formaldehyde in ethanol gave PC-1, which was reduced into a chloro-derivative PC-2. PC-2 by reacting with ethylenediamine gave a new macrocyclic ligand titled [H4L]. Its binuclear complexes with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) ions have also been synthesized. The ligand and all metal complexes have been characterized by elemental analysis, IR, 1H NMR, 13C NMR and U.V.Visible spectroscopy. Molar conductance and magnetic moment measurements have also been determined. Microanalytical data revealed 1 : 2 molar ratio of ligand to metal in all the complexes. The spectral and magnetic data indicate that Mn(II), Co(II), Ni(II) complexes show octahedral geometry with two water molecules while Cu(II) and Zn(II) complexes exhibit square planar and tetrahedral environments, respectively. The compounds show significant inhibitory activity against seven bacteria and seven fungi.

Antimicrobial polyesters containing Schiff-base metal complexes

Antimicrobial polyesters containing Schiff-base metal complexes (PSB) were prepared by polycondensation of adipoyl chloride with chelated Schiff-base diol {bis-(2-hydroxy-5-methylol-benzaldehyde)ethylenediamine}. All the metal chelated polyesters were characterized by elemental analysis, UV–Visible, FTIR, 13C and 1H NMR spectra and thermogravimetric analysis. The analytical data of the polyesters agreed with 1 : 1 molar ratio (metal chelated diols to adipoyl chloride). The geometry of the chelated polyesters was confirmed by magnetic susceptibility measurements and UV–Visible spectroscopy. The thermal behaviors of these chelated polyesters were studied by TGA (Thermogravimetric analyzer) in a nitrogen atmosphere up to 800°C. The TGA results revealed that the Cu(II) chelated polyester has better heat resistant properties than the other polyesters. The antimicrobial properties of these polyesters were investigated with agar diffusion methods against selected microorganisms Bacillus subtelillis, Bacillus megaterium, Streptococcus aureus, Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, Shigella boydii and for antifungal activity against Candida albicans, Trichophyton longifusus, Aspergillus flavus, Aspergillus niger, Fusarium solani, Microsporum canis, Puccinia graminis. The antimicrobial activity of these polyesters was higher than standard drugs Kanamycin and Miconazol.

Antimicrobial agents: synthesis, spectral, thermal, and biological aspects of a polymeric Schiff base and its polymer metal(II) complexes

Some new coordination polymers 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 studied by elemental, spectral (FT-IR, 1H-NMR, and UV-Vis), and thermogravimetric analysis. UV-Vis spectra and magnetic moments indicate that Mn(II), Co(II), and Ni(II) polymer metal complexes are octahedral, while Cu(II) and Zn(II) polymer metal complexes are square planar and tetrahedral, respectively. All compounds were screened for their antimicrobial activities against Escherichia coli, Bacillus subtillis, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Candida albicans, Agelastes niger, and Microsporum canis using the Agar well diffusion method with 100 µg mL−1 of each compound.

New class of anti‐microbial agents: Synthesis, characterization, and anti‐microbial activities of metal chelated polyurea

A new class of metal chelated polyurea have been synthesized by the reaction of toluene 2,4-diisocyanate (TDI) with chelated Schiff base diamines. The synthesized polyurea have been characterized by analytical, spectral, and thermal analysis. The results of TGA ascribed that [Cu(II)-PoU(A)] show better heat resistant properties than other metals chelated polyurea. The antibacterial activities of all the synthesized polymers were determined using the shaking flask method, where 30 mg/mL concentrations of each compound were tested against 10(5) CFU/mL solutions of S. aureus, E. coli, B. subtillis, S. typhi. The number of viable bacteria was calculated by using the spread plate method on agar plates and the number of viable bacteria was counted after 24 h of incubation period at 37 degrees C. All the polymers showed good antibacterial activity. The Cu(II) chelated polyurea show higher zone of inhibition then other due to higher stability constant and may be used in biomedical applications.

Antimicrobial Polychelates: Synthesis and Characterization of Transition Metal Chelated Barbituric Acid–Formaldehyde Resin

A monomeric Schiff base was prepared by the condensation reaction of salicylaldehyde and semicarbazide, which further react with formaldehyde and barbituric acid-formed polymeric Schiff base. Its metal polychelates were then formed with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II). All the synthesized compounds were characterized by elemental analysis, magnetic moment, FTIR, 1HNMR, and electronic spectroscopies. The elemental analysis data show the formation of 1:1 [M: L] metal polychelates. Thermogravimetric analysis was carried out to find the thermal behavior of all the synthesized polymeric compounds and thermal data revealed that all the metal polychelates are more thermally stable than their parent polymeric Schiff base. All the synthesized polymeric compounds were screened for antimicrobial activity against some clinically important microorganisms, such as Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Staphylococcus typhi, Candida albicans, Microsporum canis, and Aspergillus niger. In vitro antimicrobial activity was determined by the Agar Well Diffusion method and the result shows that all the metal polychelates exhibited better antimicrobial activity than their parent polymeric Schiff base.

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, characterization and antimicrobial activity of a new macrocycle and its transition metal complexes

The semicarbazone (L1) has been prepared by reaction of semicarbazide and glutaraldehyde (2 : 1) in distilled water and methanol (1 : 1). The reaction of semicarbazide, glutaraldehyde and diethyl oxalate in distilled water and methanol gave Schiff-base L2, 1,2,4,7,9,10-hexaazacyclo-pentadeca-10,15-dien-3,5,6,8-tetraone. Complexes of first row transition metal ions Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) have also been synthesized. The ligand and its complexes were characterized by elemental analysis, molar conductance, magnetic moment measurements, IR, 1H NMR, UV–Visible spectra and thermogravimetric analysis (TGA). Molar conductance values show that the complexes of Ni(II), Cu(II), Zn(II), Mn(II) and Co(II) are 1 : 2 electrolytes. On the basis of electronic spectral studies and molar conductance measurements an octahedral structure has been proposed for Mn(II) and Co(II) complexes, tetrahedral for Zn(II) complex and square planar for Ni(II) and Cu(II). The thermal behavior of the compounds, studied by TGA in a nitrogen atmosphere up to 800°C, reveal that the complexes have higher thermal stability than the macrocycle. All the synthesized compounds and standard drugs kanamycin (antibacterial) and miconazole (antifungal) have been screened against bacterial strains Staphylococcus areus, Escherichia coli and fungal strains Candida albicans, Aspergillus niger. The metal complexes inhibit growth of bacteria to a greater extent than the ligand.