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The interaction of Schiff base ligand A and its three metal complexes [A-Fe(II), A-Cu(II), and A-Zn(II)] with bovine serum albumin (BSA) was investigated using a tryptophan fluorescence quenching method. The Schiff base ligand A and its three metal complexes all showed quenching of BSA fluorescence in a Tris-HCl buffer. Quenching constants were determined for quenching BSA by the Schiff base ligand A and its metal complexes in a Tris-HCl buffer (pH＝7.4) at different temperatures. The experimental results show that the dynamic quenching constant (K SV ) was increased with increasing temperature, whereas the association constant (K) was decreased with the increase of temperature. The thermodynamic parameters ∆H, ∆G and ∆S at different temperatures were calculated. The ionic strength of the Tris-HCl buffer had a great influence on the wavelength of maximum emission of BSA. Under low ionic strength, the emission spectra of BSA influenced by A-Zn(II) had a small blue shift. Compared to A-Zn(II), the emission spectra of BSA in the presence of the Schiff base ligand A and A-Cu(II) had no significant λ em shift. At high ionic strength, the emission spectra of BSA upon addition of the Schiff base A, A-Fe(II), and A-Zn(II) all had a red shift, but the emission spectra of BSA had λ em shift neither at low ionic strength, nor at high ionic strength in the presence of A-Cu(II). Furthermore, the temperature did not affect the λ em shift of BSA emission spectra.

Using highly dilute method and 5-fold excess of diamine a new acyclic diamine containing pyridine moiety, N, N'-bis(2-aminoethyl)-2,6-pyridinedicarbamide (1a) was synthesized. Six novel linear polydentate Schiff base ligands containing pyridine and amide moieties, and N,N'-bis(γ-salicylideneaminopropyl)-2,6pyridinedicarbamide (2f) have been synthesized and characterized by elemental analysis, IR, UV-Vis, MS and 1 H NMR methods. The single-crystal analysis of 2e showed that it belongs to triclinic system with P-1 space group and the unit cell parameters: a＝11.010 (2) nm, b＝13.865(3) nm, c＝9.6537(19) nm, α＝102.77(2)°, β＝92.07(3)°, γ＝ 87.98(3)°, V＝1435.7(5) nm 3 , Z＝2, D c ＝1.230 mgּcm -3 , M r ＝531.66. In addition, microcalorimetric test of the inhibitory capacities of these compounds for E. coli has shown that they have antibacterial activity to different extent and that of salicylidene Schiff base is the best. The structure-activity relationship has been primarily discussed.

The antibacterial effect of a series of novel pyridine amide Schiff base compounds on Escherichia coli was investigated by a microcalorimetric method at 37 . The metabolic power ℃ -time curves of the bacteria treated by the compounds were obtained, and the thermokinetic parameters were analyzed, from which the antibacterial activities of these compounds were evaluated. The results show that two compounds F and G have good activity on aerobic multiplying metabolism of E. coli, with the value of IC 50 106 and 113 mg/L respectively, but have no effective action on the fermentation metabolism of E. coli. The action of the compounds on the non-multiplying metabolism was investigated by taking the heat output of E. coli in the stationary phase as the guideline of the activity. The experimental results revealed that the hydrophilicity of these Schiff bases had a great influence on their antibacterial activity, which results from the bacterial cell wall structure. The antibacterial structure-activity relationship of these Schiff base derivatives was also briefly discussed. The antibacterial activity of the compounds against E. coli was as follows: compound F＞G＞C＞D＞E＞B＞A.