Interaction between threonine and cadmium cation in [Cd(Thr)n]2+ (n = 1-3) complexes: density functional calculations

Structures corresponding to energy minima and the binding of cadmium cation to threo- nine (Thr) in model systems [Cd(Thr) (n) ](2+) (n = 1-3) were studied theoretically. Quantum chemical computations were performed within the framework of the density functional theory using the B3LYP, BLYP, and P functionals. In the optimized structures of the complexes [CdThr](2+) and [Cd(Thr)(2)](2+), threonine acts as a bidentate ligand and cadmium binds to oxygen atoms of carbonyl and hydroxyl groups with the formation of one and two six-mem- bered rings, respectively. In the complex [Cd(Thr)(3)](2+), cadmium binds to three nitrogen atoms and three oxygen atoms of carbonyl groups in three Thr molecules to form three five-mem- bered rings.