Designing a Novel Schiff Base Material Having NNSS Backbone

S-benzyl-β-N-(4-NN-bis 2′-chloroethylaminephenyl-methylene)dithiocarbazate(benzbz) Schiff base was synthesized by the condensation of S-benzyl-dithiocarbazate with benzaldehyde mustard in a 1:1 molar ratio. The geometrical parameters like bond length, bond angle, electron density, net atomic charge and IR frequencies were calculated using AM1, PM3, MNDO and MNDO-d semi-empirical methods. All the methods produced excellent correlation between calculated and experimental results. For IR frequencies the correlation coefficient obtained for AM1, PM3, MNDO and MNDO-d methods are 0.965973, 0.993056, 0.999154 and 0.992743 respectively. Out of all the semi-empirical methods MNDO produced maximum correlation (cc = 0.999154) between experimental and calculated vibration frequencies. Electronic charge and atom electron density data reveal the probable coordination sites in the Schiff base ligand at the time of complex formation with transition metal ions. Azomethine nitrogen and thiolsulphurcarries relatively large electron densities and hence are the preferred sites for coordination.