As a society, we are increasingly aware of the environmental impact of human activity, and consequently of the need to develop cleaner and more energy-efficient technologies in chemical synthesis. The development of efficient and selective greener methods has become a major focus of researchers worldwide and selection of appropriate alternate eco-friendly reaction media has become an integral part of this paradigm shift. Microwave (MW) irradiation as an alternative energy source in conjunction with water as reaction medium has proven to be a successful 'greener' chemical approach.
Schiff bases derived from aromatic amines and aromatic aldehydes have a wide variety of applications in many fields e.g., biological, inorganic and analytical chemistry14-18. In recent years, the acceleration of a wide range of chemical reactions using microwave dielectric heating has been reported. The solvent free conditions under microwave irradiation offer several advantages.
All the chemicals and solvent used were dried and purified by standard method and reaction were carried out under strictly anhydrous conditions. All the reactions were carried out in a domestic microwave oven (Kenstar, Model No. OM-26 E 60, Power-1200 W). Power-1200 W). The ligands were prepared by two methods. In first method microwave technique were used. In microwave method synthesis of ligands HL1 2-[1(2 Pyridinyl) ethyledene] hydrazine carbothioamide, HL2: 2-[1(2 Thienyl) ethyledene] hydrazine carboxamide, HL3 2-[1(2 Naphthenyl) ethyledene] hydrazine carboxamide, HL4 2-[1(2 Naphthenyl) ethyledene] hydrazine carbothioamide were prepared by condensation of respective ketones with thiosemicarbazide or semicarbazide presence of sodium acetate in eqimolar ratio (1.1.1) in alcoholic medium. The content was allowed to react in Teflon beaker in microwave oven using few ml of solvent. The reactions were completed in short time (4-8 min.).
In the second method the conventional heating technique was used. In this method the weight amount of thiosemicarbazide or semicarbazide hydrochloride and the respective ketones (in presence of sodium acetate) were mixed in 100mL of ethanol refluxed for 3 hrs. The crystalline products so obtained were filtered, recrystallized from the same solvent and dried.
The resulting new complexes have been characterized by elemental analyses, molar conductance, molecular weight determination and spectral studies including IR and 1H NMR spectra. The Schiff bases and their complexes have been screened for their in-vitro antibacterial (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis) and antifungal (Aspergillus niger and Pencillium chrysogenum) activities by minimum inhibitory concentration (MIC) method.
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