The wide utilization of herbicides in the crop management has created a challenging problem in terms of residual herbicides. The major problems experienced are the contamination of soil, surface water, and possibly ground water with their residues. Therefore, systematic studies are needed to evaluate the toxicity of several substituted triazines and triazoles as well as their metal complexes in order to understand the role of substituents and metal complexation in modifying the activities of herbicidal compounds containing N-heterocyclic systems. This book describes the basic chemistry of derivatization and metal complexation of selected herbicide systems that can be used as a means for modifying their activities. Accordingly, Atrazine (ATZ), Simazine (SMZ), and Amitrole (ATA) were derivatized into HAATZ, HSMZ, and NSATA respectively. Co(II), Ni(II) and Cu(II) complexes of NASTA were synthesized. All the synthesized compounds were characterized on the basis of analytical, magnetic susceptibility, conductance, IR, NMR, UV-VIS spectral studies. An octahedral geometry for Co(II)-NSATA complex and square planar geometry for Ni(II)-NSATA and Cu(II)-NSTA complexes are proposed.