Sulfur The Ureido Symmetric And Asymmetric Schiff Bases And Their Complexes

Schiff base, containing the C=N group, has some specialities: its atom N with several lone pair electronson and SP2 hybridized orbit is inclined to coordinate with metals and to be ring formation. It seems to be useful to synthesize Schiff base with chemical and biological active. Up to now , research work about this field has been done by researchers in the world, who have synthesized and charactered a plenty of Schiff base and their metal complexes, studied and exploited many uses, such as medicines , catalyst , material , titrate and simulating biology mechanism et al. Schiff base containing sulfur and its complexes are given more attention because of their significant antitumor and antibacterial activities.In this paper , we use symmetrical diamine -thiocarbohydrazide as the parent reactants, symmetrical bis-Schiff bases are easily obtained because two -NH2 groups have the same activity. Five symmetrical bis-Schiff bases have been synthesized by the reaction of thiocarbohydrazide and substituted salicylaldehydes (controlling their molar ratio 1:2) directly . However, if the reaction is carried out in the condition of a slow addition of ketone- 2-acetylpyridine to an excess of thiocarbohydrazide , controlling their molar ratio 1:1, the product of monocondensation was formed firstly, The resulting product with an additional -NH2 group may be condensed with substituted salicylaldehydes. Thus five new asymmetrical bis-Schiff bases have been synthesized. It can been seen that this method offered the possibility of a simply synthetic route to asymmetrical bis-Schiff base. Melting Point ,IR , Mass spectrum, elemental analyses and 1HNMR have been tested and their composition and probably structure are confirmed. Among these, nine have not been reported by literatures. We take asymmetrical Schiff base 2e and symmetric Schiff base 3e as representation, and two Ni(II) complexes are synthesized. Electric conduct, melting point, element analysis, IR, UV, and 1HNMR are measured, and their probablystructures have been conformed.The antibacterial activities of ten Schiff bases and two complexes have been tested against gram-positive(micrococcus aurous, bacillus subtills) and gram-negative bacterium(colibacillus). Using the international codex current method (cup-plate method), we find that Schiff bases above all have anti-bacterial ability. We measure the diameter of circles of different concentration and find that the diameter of circles do not become larger when the concentration of the compound is stronger, but have the best effect hi a certain range, However, two complexes do not have biological activity. We also compare their anti-bacterial ability and find out their concentration which showing best effect and suppose their anti-bacterial mechanism.