JCBPS; Section A; Nov. 2014 – Jan. 2015, Vol. 5, No. 1 ; 111-119 . E- ISSN: 2249 –1929 Journal of Chemical, Biological and Physical Sciences An International Peer Review E-3 Journal of Sciences Available online at www.jcbsc.org Section A: Chemical Sciences CODEN (USA): JCBPAT Research Article 111 J. Chem. Bio. Phy. Sci. Sec. A, Nov. 2014 – Jan. 2015; Vol. 5, No. 1; 111-119 Theoretical Approach of the Binary Complexation of Hg(II) with 2,4-D, MCPA and MCPP Habiba ELJAZOULI 1 , Mohamed LAABD 1 and Abdallah ALBOURINE 1* 1 Laboratory of Materials and Environment (LME), Department of Chemistry, Faculty of Sciences, Ibn Zohr University, BP 8106, Agadir, Morocco. Received: 25 November 2014; Revised: 9 December 2014; Accepted: 23 December 2014 Abstract: The experimental study of the binary complexation of phenoxy-acetic acids 2,4-D (2,4-dichlorophenoxyacetic acid), MCPA (Chloro-MethylPhenoxy acetic acid) and MCPP (Chloro-MethylPhenoxy-Propionic Acid) with mercuric ion Hg(II) has been completed by the characterization of the different ligands using a quantum computation system based on a semi-empirical method Austin Model 1 (AM1) . This review covers electronic, structural and energy aspects. We found that a more stable complexes are those with two ligands : L 2 Hg(H 2 O) 2 , L 2 Hg(OH) 2 and L 2 Hg(OH)(H 2 O) (LH : 2,4-D ; MCPA ; MCPP) and on the other hand the donor effect of substituent R in α of carboxyl group increases the stability of the complexes in passing from 2,4–D towards MCPA and MCPP and thereafter the chelating power of these ligands vis-à-vis the Hg (II) ion obeys , in agreement with the experiment, with the following order : MCPP > MCPA > 2,4-D Furthermore, the rigidity of the formed coordinate-covalent bond (formerly known as the dative bond, now obsolete) : metal-ligand moving in the same direction as that of the capacity of the three herbicides complexed Hg(II) and consequently they are complexes formed with MCPP which are more difficult to degrade and eventually more harmfull to the environment. Key words: Herbicides, Phenoxy-acetic acids, Binary complexation, Hg(II) ion, AM1.