Quantum chemical approach (DFT) of the binary complexation of Hg(II) with L-canavanine and L-arginine.

The experimental study of the complexation of the two amino acids, L-canavanine, and L-arginine, with the mercuric ion Hg(II), was completed by the characterization by a quantum calculation based on the DFT method. This study covers electronic, energetic, and structural aspects in the neutral, deprotonated, and complexed states. The atomic net charges show that the active sites of the carboxyl, guanidyl, and amino groups are the oxygen and nitrogen atoms. In fact, the L-canavanine (Can) gave stable mercuric bidentate chelates via the amino and guanidyl groups. Hg(Can)(H 2 O) 2 , Hg(Can) 2 and Hg(OH)(H 2 O)(Can), while the L-arginine (Arg) resulted in engagement of carboxyl and amino groups to bidentate complexes: Hg(Arg)(H 2 O) 2 , Hg(Arg) 2 , Hg(Arg)(OH)(H 2 O). The metal-ligand coordination bond is more rigid with the guanidyl and carboxyl groups than with the amino group; and the bond formed with the amino group is more rigid in the L-canavanine than L-arginine.