Synthesis, Characterization And Antibacterial Activities Of Schiff Bases With 2-hydroxyl-1-naphthaldehyde And Theirs Transition Metal Complexes

The paper based on 2-hydroxyl-1-naphthaldehy(HNL) which have high conjugate property and strong steric hinder effect of naphthyl ring, and can form more coordinated point of Schiff bases and fantastic transition metal complexes in structure and capability. In this paper, five schiff bases and its eighteen transition metal complexes were prepared with 2-hydroxyl-1-naphthaldehy and different amines, and their structures, spectra and antibacterial activities were also studied. The main work are as following:1).The Schiff base ligands N-o-phenylenediamine-(2-hydroxyl-1-naphthaldehy) (HL¹),N,N'-o-phenylenediaminebis-(2-hydroxyl-1-naphthaldehy) (H₂L²), which from the reaction of o-Phenylenediamine and 2-hydroxyl-1-naphthaldehyde, and theirs eight transition metal complexes ZnL¹Â·C₂H₅OH(1), NiL¹Â·C₂H₅OH(2), Mn(L¹)₂·CH₃COO)(3), CuL¹Â·C₂H₅OH(4), ZnL²Â·C₂H₅OH(5), NL²Â·CH₃COOH(6),MnL²Â·CH₃COO(7), CuL²Â·C₂H₅OH(8) were synthesized and characterized by elemental analysis, IR, UV-Vis, TG, etc. The result indicated metal ions in complexes (1), (2), (4), (5), (6) and (8) were existed in tetra-coordinated form, and in complexes (3) and (7), metal manganese ion was hexa-coordinated environment, the CH₃COO^- in complex (3) was not coordinated, but in complex (7), manganese ion coordinated also with two oxygen atoms from acetic acid. (All these complexes have the same or different structure because of different ligands or metal ions.) The fluorescent analysis of ligand H₂L² and complex (5) indicated they all occured Einstein shift compared with HNL. The reason is that, excitated energy reduce in schiff bases and zinc complexes, resulted in fluorescent emission apex Einstein shift.2). The ligand N,N'-ethylenedianinebis-(2-hydroxyl-1-naphthaldehy) (H₂L³) and its four transion metal complexes ZnL³Â·2H₂O (9), NiL³ (10), MnL³Â·Ac (11), CuL³ (12) were synthesized , and a single crystal of complex (10) was also obtained by the methods of solvent diffuse. The structure of (10) shows the Ni²⁺ is in four-coordinated plane environment, each two complexes molecule form a dimer through p-p interaction of naphthyl ring and two C-H^…O hydrgon bonds, and a three dimensional structure is constructed by the dimer as unit through C-H^…0 hydrgon bonds. The structure of complex (12) was similar to (10), but complexes (9) and (11) may form a hexa-coordinated octahedron environment, in complx (11) the metal manganese ion was trivalence. It can be see that different metal acetic acid salt react with the same ligand can get complex with different coordinated forms. The TG analysis indicated that the decomposed temperature of complex (9) is at 420℃, higher than the ligand after one water molecule is eliminated. It means Zn²⁺ can improve the decompose temperature.3). Schiff ligands N,N'- diethylenetriaminebis-(2-hydroxyl-1-naphthaldehy) (H₂L⁴), N,N'- triethylenetetraminebis-(2-hydroxyl-1-naphthaldehy) (H₂L⁵) and theirs five complexes ZnL⁴(13),CuL⁴(14),ZnL⁵(15),NiL⁵(16),CuL⁵(17) were synthesized and characterized by elemental analysis, IR spectra, UV-visible spectra and TG-DTA analysis, etc. These complexes have similar coordinated environments. The TG showedthe heat decompose temperature of complex (13) more higher than corresponding ligand H₂L⁴. This indicated the thermal stability of ligand is increased after it coordinateto metal ion. The thermal decompose temperature of complexes (15) and (16)were also higher than their ligand, but theirs thermal stability is lower than complex (13).4). The antibacterial activities of five ligands and theirs copper complexes (4),(8),(12),(14),(17) against two kind of bacterias- Staphylococcus aures and bacillus subtilis were measured, the result indicated they all have better antibacterial activities, and the complexes were higher to corresponding ligands. Also, the antibacterial time was long. The complex (14) has the maximal antibacterial activities and longest antibacterial ability.